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Citation: Yannis, G.; Michelaraki, E.
Review of City-Wide 30 km/h Speed
Limit Benefits in Europe.
Sustainability 2024,16, 4382. https://
doi.org/10.3390/su16114382
Academic Editor: Rosolino Vaiana
Received: 19 March 2024
Revised: 8 May 2024
Accepted: 16 May 2024
Published: 22 May 2024
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sustainability
Review
Review of City-Wide 30 km/h Speed Limit Benefits in Europe
George Yannis and Eva Michelaraki *
Department of Transportation Planning and Engineering, National Technical University of Athens, 5 Heroon
Polytechniou Str., 15773 Athens, Greece; geyannis@central.ntua.gr
*Correspondence: evamich@mail.ntua.gr
Abstract:
To date, more and more European cities are systematically working to expand the pro-
portion of their street network with a speed limit of 30 km/h. This paper endeavored to assess
the effectiveness of city-wide 30 km/h speed limits in Europe. In an effort to condense research
outputs, a quantitative approach along with qualitative assessments were implemented. This study
described the changes in safety, environment, energy, traffic, livability, and health before and after the
phased implementation of city-wide 30 km/h speed limits. The systematic review was conducted
following the Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) guide-
lines. Results from 40 different cities across Europe, including Brussels, Paris, and Zurich, indicated
that reductions in speed limits improved road safety by decreasing the likelihood of crash risk and
the severity of crashes that do occur. On average, the implementation of 30 km/h speed limits in
European cities demonstrated a 23%, 37%, and 38% reduction in road crashes, fatalities, and injuries,
respectively. Lower speed limits also yielded environmental benefits, with emissions decreasing on
average by 18%, noise pollution levels by 2.5 dB, and fuel consumption by 7%, indicating enhanced
fuel efficiency and reduced environmental impact. Encouraging citizens to embrace walking, cycling
and utilizing public transit services can further contribute to a safer and environmentally sustainable
urban environment.
Keywords:
30 km/h speed limits; road safety; speed limit reduction; cities;
implementation modalities
1. Introduction
The European Union’s road safety policy framework for 2021–2030 aims to achieve a
50% reduction in road deaths and serious injuries by 2030, with the ultimate goal of “zero
deaths on the roads” by 2050, known as “Vision Zero” [
1
]. Vision Zero is a comprehensive
strategy which aims to completely eliminate all traffic fatalities and serious injuries, and
promote healthy, safe, and equitable mobility for all road users. First implemented in
Sweden in the 1990s, Vision Zero states that any serious or fatal injuries that occur within
the road system are unacceptable. This approach is supported by time-limited targets and
performance indicators aiming to reduce fatalities and slight and serious injuries [2].
In order to achieve “Vision Zero” in the European Union (EU), the Safe System
Approach is promoted [
3
]. This Safe System prioritizes safer vehicles, infrastructure,
lower speeds, and improved post-collision care. In particular, special emphasis is given
to safer vehicles through the implementation of regulations and standards for advanced
safety features. Additionally, efforts are directed toward enhancing road infrastructure
design and maintenance to minimize the risk of collisions and reduce crash severity. Speed
management strategies, including lower speed limits in residential streets and effective
enforcement, are also crucial to promote safer driving behavior. Improving emergency
response systems and post-collision care facilities is essential for better treatment of crash
victims and reducing injury severity. Cross-border cooperation is prioritized to enforce
traffic regulations consistently across EU member states, while digitalization of driving
licenses enhances license management and enforcement.
Sustainability 2024,16, 4382. https://doi.org/10.3390/su16114382 https://www.mdpi.com/journal/sustainability
Sustainability 2024,16, 4382 2 of 28
The implementation of City 30, which enforces a maximum speed limit of 30 km per
hour (km/h), aligns with urban sustainability goals, including those outlined in the Cities
Mission aiming for zero climate impact by 2030. It serves as a foundational element for
initiatives such as the ‘Green Footprint’ project. By prioritizing spaces conducive to slow
mobility, cycling, and walking, City 30 aims to contribute to sustainable urban development.
It seeks to promote a variety of transportation modes, enhance safety for pedestrians and
cyclists, and foster community engagement and interaction.
In contemporary cities, ensuring traffic safety remains a top priority, prompting gov-
ernment bodies and policymakers to implement strategies aimed at improving road safety
and promoting walking and cycling. One such strategy involves lowering speed limits,
particularly in areas with high pedestrian density, as a means to reduce the frequency and
severity of traffic crashes. Numerous studies have consistently shown that higher speeds
increase the chances of being involved in a crash and the severity of resulting injuries [
4
,
5
].
By driving at lower speeds, drivers have more time to react to unexpected events, thereby
preventing crashes or lessening their impact. Consequently, the implementation of reduced
speed limits in residential areas, city centers, and streets with heavy pedestrian traffic is
anticipated to decrease noise levels, promote active modes of transportation, and positively
influence urban livability [6–8].
To date, several European cities, including Brussels and Paris, are actively pursuing
efforts to systematically increase the portion of their street networks governed by a 30 km/h
speed limit, either across the entire city or within designated city regions. Many of these
cities have adopted a broad implementation of a 30 km/h speed limit as a standard measure,
designating it as the default unless otherwise signposted. The adoption of this approach
indicates a broader trend toward prioritizing pedestrian safety and urban livability.
This study aims to critically assess the effectiveness of city-wide 30 km/h speed limits.
To achieve this objective, a thorough literature review was implemented and the benefits
from 30 km/h speed limits in 40 cities across Europe were provided. This paper described
the changes in safety, environment, energy, traffic, and livability, before and after the phased
implementation of city-wide 30 km/h speed limits.
This paper is structured as follows: First, the overall concept and the motivation of
this study is presented, emphasizing the key principles of Vision Zero and Safe System
Approach. In the next chapter, the theoretical background with the benefits of lowering
speed limits in cities is given. Then, the methodology of this study is provided. This
is followed by the cornerstone chapter of the paper covered by an extensive literature
review implemented with respect to the effectiveness of city-wide 30 km/h speed limits
measuring road safety, traffic efficiency, environmental impacts, etc., in several European
cities. The results of the study are then presented, enabling the emergence of road safety-
related conclusions. Finally, the main findings are highlighted and recommendations for
implementation modalities are also discussed.
2. Background
Reducing speed limits in cities to appropriate levels, such as 30 km/h, can poten-
tially save lives, prevent road crashes, and reduce injuries among all road users. The
improvements in both actual and perceived safety and comfort for road users result in
positive outcomes across various societal well-being indicators, including safety, health,
energy conservation, environmental preservation, accessibility, equality, and economic
prosperity [
9
,
10
]. Research and scientific evidence suggest that these benefits have direct or
indirect economic implications, often quantifiable [11,12].
The enforcement of speed limits is the most effective measure in order to manage
operating speeds [
13
]. It should be noted that speed enforcement yields optimal results
when it is difficult to avoid, when it is continued over a long period of time, and when
there is a mix of highly visible and less visible activities. Moreover, it is effective to focus
on speed enforcement in situations, roads, and times where speeding is having the most
effect on road safety levels. To begin with, speed limits were primarily implemented in
Sustainability 2024,16, 4382 3 of 28
order to reduce the frequency and severity of crashes and decrease the generalized cost
associated with road incidents [
14
]. This countermeasure was introduced with the intention
of addressing the fact that up to 30% of casualty crashes occurred in cities.
Moreover, lower speeds can directly benefit the environment through the reduced
direct and indirect emissions. Specifically, higher speed limits in urban environments
are associated with harsh acceleration and braking [
15
]. Calmer and slower driving can
decrease emission rates of carbon monoxide, volatile organic compounds, and oxides of
nitrogen emission rates by up to 17%, 22%, and 48%, respectively, depending on the driver’s
aggressiveness and the gear engaged [
16
]. An interesting study conducted by Duong and
Lee [
17
] revealed that vehicle speed contributes to the extent of heavy metal contamination,
including lead, cadmium, zinc, and nickel found in road dust.
The implementation of 30 km/h speed limits in cities can yield broader public health
benefits beyond just reducing fatalities and serious injuries. These include substantial
advantages, such as diminished noise pollution, lower rates of obesity, and increased
engagement in active transportation. According to Zijlema et al. [
18
], utilizing active
transport modes improves mental health, while Warburton and Bredin [
19
] have noted
that active transportation is associated with a reduced risk of over 25 chronic diseases and
promotes longevity.
Studies have shown that traffic-induced noise is the primary source of noise pollution
in cities, accounting for approximately 80% of all communal noise sources. In urban
environments where speeds range from 30 to 60 km/h, reducing the speed limit by just
10 km/h can lead to decreased noise levels by up to 40%. Vienneau et al. [
20
] implemented a
comparative risk assessment in Lausanne, Switzerland (i.e., comparing areas with 30 km/h
speed limits to a reference scenario without such limits) and results demonstrated that
4700 years of life lost were attributable to road traffic noise. It was also estimated that in the
lower speed limit scenario, 1 cardiovascular death, 17 diabetes cases, as well as 72 hospital
admissions from cardiovascular disease annually could be prevented [21].
In recent decades, road designs have predominantly prioritized motorized traffic
without adequately considering streets as public spaces or ensuring all road users’ safety.
However, practitioners are increasingly moving away from the idea that there should
always be a trade-off between safety and speed. Within the framework proposed by
Corben [
22
], known as “movement and place”, both mobility and safety concerns can be
addressed simultaneously, rather than treating them as conflicting priorities. By imple-
menting speed limits that are tailored to the specific requirements of a road, considering its
function as both a “place” and a pathway for “movement”, communities can foster more
vibrant and livable environments [23].
Enforcing safe speeds can enhance accessibility and consequently reduce the division
caused by roads functioning as barriers within cities. In areas with high levels of motorized
traffic and fast-moving vehicles, walking can be discouraged, and social interactions among
residents living on opposite sides of the road may be limited. This severance can particularly
impact communities in residential areas, potentially impeding children from safely crossing
roads to reach school or hindering workers from commuting safely between their residences
and nearby workplaces.
Lowering speed limits is often met with resistance due to concerns about potential
increases in travel times and traffic congestion. However, research generally indicates
that any such impacts range between 3 and 5%, and in some cases, reducing speed limits
can even lead to improvements in travel times and congestion levels [
24
]. Despite fears
that lowering speed limits may result in slower travel, studies suggest that the benefits
in terms of improved safety and other factors often outweigh any change in travel times.
The relevant change is usually lower than most people intuitively assume. This may be
due to the fact that in dense urban areas, the proportion of the time that can be driven
considerably more than 30 km/h is quite low, especially during the times of day when
most car journeys take place.
Sustainability 2024,16, 4382 4 of 28
Interestingly, speed limit reduction can sometimes lead to improvements in travel
times by smoothing traffic flow and reducing bottlenecks. From an economic standpoint,
optimal speeds are those that minimize costs related to safety, emissions, journey time,
and other relevant factors. According to Hosseinlou et al. [25], these optimal speeds often
tend to be lower than the existing speed limits, highlighting the potential advantages of
lowering speed limits for overall road efficiency and safety.
To date, there is limited scientific evidence with regard to the city-wide 30 km/h speed
limit benefits. This forms the motivation of the current research, which aims at assessing the
effectiveness of 30 km/h speed limits in Europe in terms of safety, emissions, energy, traffic,
livability, and health. Particular emphasis in the current research will be given to highlight
the effectiveness of city-wide 30 km/h speed limits and provide valid suggestions that
could be an effective strategy for reducing road crashes, fatalities, and injuries. It is crucial
to realize that in Europe where big parts of the cities are dense, city-wide 30 km/h speed
limits are proven to save thousands of lives. The policy recommendation that would follow
from this study is to implement city-wide 30 km/h speed limits, rather than 30 km/h speed
limits in restricted areas of a city.
3. Methodology
The current study undertakes a comprehensive evaluation of the effectiveness of
30 km/h speed limits in cities. To achieve this objective, an extensive literature review was
conducted, focusing on changes in various parameters such as safety, environment, energy
consumption, traffic patterns, livability, and public health before and several months (or
1–2 years) after the phased implementation of city-wide 30 km/h speed limits. Stringent
selection criteria were employed to incorporate studies into this review, which involved
assessing factors such as publication date, study quality, and relevance, as well as the
overall credibility and validity of the publication sources. This methodological approach
ensures the inclusion of research findings, allowing for the assessment of the impacts
associated with the adoption of lower speed limits in cities.
It should be clearly emphasized that the estimated health benefits associated with
the current speed limits, as well as additional benefits that could be obtained by the
implementation of additional 30 km/h speed limits, can be indirectly revealed through
factors such as noise reduction, decreased number of deaths from cardiovascular disease,
decreased hospital admissions from cardiovascular disease, decreased incidence of diabetes,
as well as reduced levels of annoyance and sleep disturbance in individuals.
3.1. Literature Search
To critically assess the effectiveness of implementing a 30 km/h speed limit in cities,
a systematic search across scientific articles and gray literature sources was conducted
using the key terms outlined in Table 1. While numerous studies, articles, and commer-
cial websites explore the benefits of speed limit reductions for road safety, this literature
review specifically focused on research aimed at objectively determining the impact of
city-wide 30 km/h speed limits across various domains including safety, environment,
energy consumption, traffic flow, livability, and public health.
Following the establishment of inclusion criteria, the identified key terms were sys-
tematically entered into the relevant databases. The inclusion criteria for selecting relevant
studies were as follows:
−The search term should be present in the title, abstract, or keywords of the study.
−Studies should have been published from 1992 onwards.
−
Studies should include information related to the 30 km/h speed limit in the title
or abstract.
−
Sources should prioritize scientific journals over peer-reviewed conference papers,
followed by scientific reports, articles, or websites.
−Only studies published in English were considered for inclusion.
Sustainability 2024,16, 4382 5 of 28
These criteria were meticulously applied to ensure the selection of studies meeting
stringent quality and relevance standards, thereby facilitating a thorough and credible
assessment of the effectiveness of 30 km/h speed limits in urban environments.
Table 1. Search terms and screened and included papers.
Key Search Review Search Terms Screened
Papers
Included
Papers
30 km/h speed limit
“30 km/h” OR “20 mph” OR “30 km/h speed limit” OR “speed
limit” OR “speed limit reduction” OR “maximum speed” OR
“reduced speed” AND “traffic calming” AND “city-wide”
AND “cities” AND “implementation modalities”
589 70
The search process was conducted across various databases, including ScienceDirect,
Scopus, ResearchGate, Google Scholar and PubMed. Initially, publications were identified
and screened based on their titles, resulting in 589 potential research articles. Subsequently,
these publications underwent further assessment through abstract screening to determine
their relevance to the study’s objectives. The limitation was set to include publications
from 1992 onwards, with a focus on peer-reviewed English language scientific journals,
conference papers, articles, websites, and scientific reports for inclusion. In order to enhance
the comprehensiveness of the search, additional relevant search terms were incorporated.
Following a thorough screening process, a total of 70 publications were deemed suitable
for inclusion in the review. The literature predominantly focused on the topic of 30 km/h
speed limits, providing a robust foundation for the critical review and assessment of their
effectiveness in urban settings.
Regarding the issue of potential sources of bias, seasonal variations may impact traffic
patterns and safety outcomes, potentially complicating the interpretation of the results.
To address this concern, a comprehensive analysis that accounted for seasonal trends
was conducted by comparing safety outcomes during the post-implementation period to
historical data from the same time period in previous years (if available). An attempt was
made to include comparisons over long periods of time. However, in many cases, no data
were available in scientific papers or articles. As a result, comparisons with several months
later were included in the analysis in order to provide an overall depiction of the findings
for European cities.
3.2. The PRISMA Procedure
The review conducted in March 2024 adhered to the Preferred Reporting Items for
Systematic Reviews and Meta-Analyses (PRISMA) guidelines to ensure the systematic
identification of relevant research articles [
26
]. Recently updated to incorporate advance-
ments in both conceptual and practical methodologies for selecting, identifying, assessing,
and synthesizing studies [
27
], this review aimed to provide a comprehensive analysis of
the effectiveness of 30 km/h speed limits in cities. The initial search was conducted in
March 2023, with all databases accessed for the last time in May 2024.
Regarding the PRISMA framework, it serves as a valuable guideline for transparently
reporting systematic reviews and meta-analyses. It aids in the identification of relevant
studies by facilitating a structured approach to literature search, screening, and selec-
tion based on predefined criteria. PRISMA ensures that the review process is conducted
rigorously and transparently, thus enhancing the credibility and reproducibility of the
findings.
As for assessing study quality, this approach involved a comprehensive evaluation of
various methodological aspects to ensure the trustworthiness and reliability of the included
studies. This assessment typically encompasses factors such as study design, sample size,
data collection methods, and risk of bias. Validated tools and specific criteria to the study
type were also employed in order to systematically appraise the strengths and limitations
Sustainability 2024,16, 4382 6 of 28
of each article. Potential bias, such as the COVID-19 pandemic, short-term effect of a speed
reduction, or demand changes were also highlighted.
Moreover, it is crucial to acknowledge the inherent complexity of evaluating study
quality, especially given the diverse nature of research methodologies and contexts. There-
fore, the proposed assessment incorporates a nuanced interpretation of findings, taking into
account the overall body of evidence and the consistency across studies. Particular empha-
sis was given to prioritize transparency in reporting the assessment criteria and decisions,
enabling readers to critically appraise the evidence and draw informed conclusions.
Figure 1provides an overview of the PRISMA flowchart and the search strategy
followed.
Sustainability 2024, 16, x FOR PEER REVIEW 6 of 28
sample size, data collection methods, and risk of bias. Validated tools and specific criteria
to the study type were also employed in order to systematically appraise the strengths
and limitations of each article. Potential bias, such as the COVID-19 pandemic, short-term
effect of a speed reduction, or demand changes were also highlighted.
Moreover, it is crucial to acknowledge the inherent complexity of evaluating study
quality, especially given the diverse nature of research methodologies and contexts.
Therefore, the proposed assessment incorporates a nuanced interpretation of findings,
taking into account the overall body of evidence and the consistency across studies.
Particular emphasis was given to prioritize transparency in reporting the assessment
criteria and decisions, enabling readers to critically appraise the evidence and draw
informed conclusions.
Figure 1 provides an overview of the PRISMA flowchart and the search strategy
followed.
Figure 1. PRISMA flowchart of the systematic literature review.
The search yielded a total of 1279 papers, of which 589 were identified as duplicates.
Two reviewers independently screened all papers using a general inclusion/exclusion
assessment, following a methodology similar to that of Hawker et al. [28]. A total of 126
articles were selected for full-text review, comprising full papers, articles, websites, and
commercial reports recommended by a subject maer expert. Following the full paper
review, an additional 56 articles and reports were excluded for not meeting the inclusion
criteria. Ultimately, 70 papers, commercial reports, and websites were included in the final
review.
4. Literature Review Findings
Scientific evidence has demonstrated that the introduction of city-wide 30 km/h speed
limits has resulted in saving more than 37% of lives, alongside positive impacts on the
environment, energy consumption, and public health through reduced fuel consumption
and increased walking and cycling. Currently, numerous cities worldwide have begun
implementing 30 km/h speed limits in substantial portions of their urban areas. Below, a
Figure 1. PRISMA flowchart of the systematic literature review.
The search yielded a total of 1279 papers, of which 589 were identified as duplicates.
Two reviewers independently screened all papers using a general inclusion/exclusion
assessment, following a methodology similar to that of Hawker et al. [
28
]. A total of
126 articles were selected for full-text review, comprising full papers, articles, websites, and
commercial reports recommended by a subject matter expert. Following the full paper
review, an additional 56 articles and reports were excluded for not meeting the inclusion
criteria. Ultimately, 70 papers, commercial reports, and websites were included in the final
review.
4. Literature Review Findings
Scientific evidence has demonstrated that the introduction of city-wide 30 km/h speed
limits has resulted in saving more than 37% of lives, alongside positive impacts on the
environment, energy consumption, and public health through reduced fuel consumption
and increased walking and cycling. Currently, numerous cities worldwide have begun
implementing 30 km/h speed limits in substantial portions of their urban areas. Below,
a detailed description of the effectiveness of the 30 km/h speed limit in various cities is
provided, focusing on safety, emissions, noise, energy usage, traffic flow, livability, and
public health. It is worth noting that only cities with populations exceeding 200,000 were
considered in this study. Lastly, it should be mentioned that for the majority of cities
Sustainability 2024,16, 4382 7 of 28
examined, data collected came from speed measurements carried out by LIDAR cameras
outside the radar zones to avoid the bias of slowdowns dictated by fear of the police.
Previous research on the effectiveness of city-wide 30 km/h speed limits in Europe
is limited and lacks some important aspects. Thus, this study addresses a gap in the
state-of-the-art literature by assessing the impact of reducing speed limits, focusing on the
case of several European cities. The evaluation of 30 km/h speed limits on a city-wide and
urban environment level is a novel undertaking. The present work presents a complete
framework to evaluate the benefits of reducing default speed limits, which can be adopted
by other cities worldwide. The conclusions drawn from this research could contribute to a
more comprehensive understanding of the effectiveness of speed limit reductions. These
findings may have an impact on future policies and initiatives, promoting safer roads for
all users worldwide.
4.1. Safety
First of all, it is worth highlighting that due to the COVID-19 pandemic, 2020 was
not a typical year in terms of mobility and road safety. The COVID-19 pandemic had an
impact on traffic in EU27, with a corresponding reduction in road crashes, fatalities, and
injuries following the introduction of lockdown measures. As a result, for those cities
which have implemented speed limit reductions in 2020, part of the exposure reduction can
be attributed to the introduction of 30 km/h speed limits, but there are also other crucial
parameters that might have led to the relevant decrease (e.g., change demands, traffic
patterns).
Most cities implemented the changes fairly recently and just before or during the
pandemic (most in 2020 and 2021). Consequently, there is no well-documented knowledge
about results from all cities, and existing knowledge mainly concerns more immediate
effects such as reduced speed, traffic crashes, noise, air pollution, etc. An attempt was
made to take the year 2019 as a reference taking into account the confinements and traffic
restrictions on the years 2020 and 2021 which make them non-representative years. The
assessment was conducted relatively soon after introducing the intervention.
Findings from the literature review revealed that during the COVID-19 pandemic,
average speed increased by 6–11% while a 22% increase in the drivers exceeding the speed
limit was observed compared to the 2018–2019 average [
29
]. Thus, the decreased mobility
patterns along with the reduced number of traffic volumes led to a reduction in road crashes
and fatalities. This is contradictory with the results derived from the implementation of
a 30 km/h speed limit for all cities examined in which lower average driving speeds of
up to 7% were found. After this measure, drivers reduced their mean speed and drove
conservatively and more carefully which led to improvement of road safety, through
the reduction in road crashes and fatalities. Taking the abovementioned arguments into
consideration, the study was based on only a few cases (18 out of 40), which in return
indicated good results, in which the effect of COVID-19 was not taken into account.
However, it is important to emphasize that it is still too early to document long-term
consequences and draw definitive conclusions. While trends from other cities suggest
that similar results can be expected over time, it is evident that the 30 km/h speed limit
represents a crucial step toward creating safer, more livable cities with fewer road crashes,
fatalities, and serious injuries. Although it will take more time to measure and verify these
outcomes, knowledge from previous studies has generated clear expectations that reduced
speed limits, and vehicular speeds on streets will contribute to such results. The consistent
findings across diverse cities suggest that the study may indeed be useful for discussions
on the implementation of a general speed limit of 30 km/h in cities.
To begin with, in September 2023, Wales, United Kingdom (UK), has instituted an
urban speed limit of 30 km/h, reflecting a comprehensive effort to enhance road safety
and improve the overall urban environment [
30
]. This measure was designed to reduce
crash risk, create safer streets for pedestrians and cyclists, and promote a more sustainable
and community-friendly approach to transportation. However, the effectiveness of the
Sustainability 2024,16, 4382 8 of 28
introduction of 30 km/h speed limit on road safety in Wales has not been examined yet.
Starting on 8 December 2023, Amsterdam, The Netherlands, reduced the speed limit on
most of its roads (i.e., 80% of Amsterdam’s roads) to 30 km/h [
31
]. With the new speed
limit, it is expected to have a 20–30% reduction in serious crashes [32].
In January 2021, Brussels, Belgium, implemented a city-wide 30 km/h speed limit.
Under this policy measure, the maximum speed is set at 30 km/h on all roads in the
Brussels Capital region, except for major thoroughfares where the speed limit remains at
50 or 70 km/h
. Despite being a new initiative for the city, improvements in road safety
were observed. In particular, five months after the introduction of the general 30 km/h
speed limit, there was an overall 10% reduction in road crashes (i.e., dropping from 708
in the last quarter of 2020 to 635 in the first quarter of 2021). Specifically, during the first
quarter of 2021, there were 635 road crashes compared to 814 during the same period in
2020 (i.e., the first quarter of 2020). Findings from Brussels revealed that the reduction in
average speed had no impact on journey times. In particular, slightly shorter journey times
were observed. Nevertheless, to mitigate any bias stemming from the coronavirus crisis
lockdown, these figures were compared with those from the last quarter of 2020, which
recorded 708 road crashes [33].
This decrease was also noticeable for serious injuries in Brussels, where a 37% reduc-
tion (i.e., from 38 in the fourth quarter of 2020 to 30 in the first quarter of 2021) in serious
injuries was identified [
34
]. It is worth noting that the number of serious injuries was
down from 46 in the first quarter of 2020 to 30 in the first quarter of 2021. One year later,
a 20% reduction in serious injuries was observed, while fatalities also fell from 13 (2018)
and 11 (2020) to 5 in 2021; an overall 55% reduction in the total number of fatalities in
2021 compared to 2020 was found [
35
]. Nevertheless, it should be clearly mentioned that
a large part of this reduction (
−
55% in the number of fatalities) can be attributed to the
introduction of the 30 km/h speed limits, but there are also other crucial parameters that
might led to this decrease, such as the COVID-19 pandemic. Interestingly, according to
Moore [
34
], the main reduction was found in crashes with vulnerable road users, such as
pedestrians and cyclists.
Similarly, in August 2021, Paris, France, initiated the reduction of speed limits to
30 km/h on 60% of Parisian roads, taking concrete steps to enhance road safety and
mitigate noise and air pollution. Several months after the implementation of this measure,
a 25% decrease in the number of bodily injuries and a 40% decrease in serious and fatal
crashes was achieved [
36
]. The corresponding percentages are exempt from potential bias
relating to the COVID-19 pandemic. Findings from Münster, Germany, where 30 km/h
speed limits were introduced in July 2021, revealed that one year after the implementation
of the 30 km/h speed limit, there was a 72% decrease in the number of people severely
injured in road crashes [
37
]. In November 2021, Zurich, Switzerland, implemented 30 km/h
speed limit restrictions on parts of its street network to reduce noise levels and improve
residents’ health and quality of life. Following this measure, a 25% reduction in road
fatalities was observed. Additionally, the incidence of car–pedestrian crashes was reduced
by 16%, and the number of injured pedestrians decreased by 20% [38].
With the aim of encouraging the micromobility in the city of Bologna, Italy, from July
2023, the speed limit dropped to 30 km/h. Three months after the implementation of this
measure, road crashes have fallen by 14.5% compared to the same period in 2023 [
39
].
According to the data provided by local authorities, in the period between 15 January and
14 April 2024, there was a 13.4% decline of crashes with injuries and 17% of crashes without
injuries compared to the previous year. It was also revealed that there was a 14.7% drop in
pedestrians involved in crashes (i.e., from 102 in 2023 to 87 in 2024).
Moreover, in June 2018, Bilbao, Spain, reduced the speed limit to 30 km/h aiming
to improve road safety, public health, and quality of life for residents as well as reduce
noise and air pollution. Two years later, in September 2020, 30 km/h speed limits were
set for the entire city. Between 2019 and 2020, the city had reduced the number of road
crashes by 28% [
40
]. This decrease was mainly due to the implementation of 30 km/h speed
Sustainability 2024,16, 4382 9 of 28
limits; however, it is unclear if part of this reduction could be attributed to the COVID-19
pandemic. Overall, it is important to point to the evidence from Spain, where the speed
limit on the majority of roads was changed from 50 to 30 km/h in 2019. After two years of
implementation (2019–2021), Spain has reported a 20% reduction in urban road deaths, with
fatalities reduced by 34% for cyclists, 31% for the elderly, and 24% for pedestrians. In order
to explain this reduction in road deaths in Spain, it should be mentioned that the 30 km/h
speed limit on single-lane streets in each direction came into effect in September 2020.
In 2004, Helsinki, Finland, introduced widespread 30 km/h speed limit restrictions,
which were later expanded in 2019. Initially implemented in the city center and certain
residential areas, these speed restrictions were eventually extended to encompass almost
all streets. Following the implementation of this measure, streets with lower speed limits
experienced a 9% decrease in road crashes resulting in personal injury. Moreover, in areas
where the speed limit was reduced from 40 to 30 km/h, a 19% decrease in pedestrian injuries
and a 34% decrease in vehicle damages were observed. The most important improvement
occurred in the city center, where traffic-related injuries dropped by 42% [
41
]. In 2019,
coinciding with the city-wide introduction of the 30 km/h speed limit, there were no
pedestrian or cyclist fatalities in road crashes. Luxembourg has also expanded its city-wide
30 km/h speed limit to cover all built-up areas, mirroring Helsinki’s initiative, where not a
single pedestrian or cyclist was killed in road crashes in 2020 compared to 2021 [42].
In general, close to 200 cities in France have introduced a 30 km/h speed limit so
far, including Grenoble, Nantes, and Lille. More specifically, in 2016, Grenoble, France,
extended traffic to 30 km/h throughout the country. In 2016 and 2017, 43 of the 49 munici-
palities in the metropolitan area gradually joined this approach, with 30 km/h becoming
the rule, making the metropolis the first major urban area to implement the generalization
of 30 km/h. There was a reduction in the number and severity of road crashes, with
pedestrians in particular spared from crashes [
43
]. An intriguing study found that the
number of pedestrians killed or injured in Grenoble had decreased by 50% since the city
implemented a 30 km/h speed limit [
44
]. What is more, road crashes seem to be decreasing,
in number and severity, and pedestrians were particularly spared from crashes.
Similarly, in March 2022, Lyon, France, implemented city-wide 30 km/h speed limit
aiming to improve the well-being and health of its residents. One year later, an initial
encouraging assessment was drawn up; crash rates dropped by 22%, while hospitalized
injuries decreased by 40% [
45
]. In addition, Lille, France, was another city which has an-
nounced a 30 km/h speed limit from January 2021, aiming to improve road safety and make
the city streets quieter to encourage more active modes of transport. On
19 August 2020
,
the council began dropping the city-center speed limit from 50 to 30 km/h with the aim of
turning 88% of Lille’s roads into 30 zones, except for main roads. With only 44% of its roads
having a 30 km/h speed limit back in October 2019, this was a major step and represented
rapid progress. In August 2020, Nantes went into the 30 km/h speed limit in more than
80% of the urban roads, while one year later, Montpellier also started the implementation
of 30 km/h zones. New signs have been installed at the entrances to the built-up area,
identified by road markings, while zones remaining at 50 km/h were exceptions [46].
In July 2016, Edinburgh, UK, reduced the speed limit on nearly all of its roads (e.g., city
center, main streets, and residential roads) from 30 miles per hour (mph) to 20 mph (roughly
30 km/h). One year after the extensive evaluation of 20 mph speed limits, a 38% drop was
observed, with 371 fewer crashes compared to the previous year. This decrease included
fewer crashes involving cyclists and pedestrians [
47
]. A breakdown of the casualty figures
revealed that one year later, the number of fatalities dropped by 23% (i.e., 11 fewer fatalities
compared to the previous year) while the number of serious injuries fell by 33% [
48
]. In
a recent study, Abohassan et al. [
49
] examined the effectiveness of speed limit reduction
in Edmonton. It was revealed that the overall number of collisions and injuries as well as
fatalities resulting from collisions decreased by 25% and 31%, respectively.
In addition, in June 2016, London, UK, has implemented 20 mph (30 km/h) zones. The
implementation of 20 mph zones resulted in an overall 46% decrease in death and serious
Sustainability 2024,16, 4382 10 of 28
injury crashes, with a 50% reduction specifically for children aged 0–15 inside the zones.
Monitoring of the 20 mph schemes by Transport for London [
50
] revealed reductions in
collisions since the implementation of this measure. The number of collisions decreased by
25% (i.e., from 406 to 304), and collisions resulting in death or serious injuries also decreased
by 25% (i.e., from 94 to 71), highlighting the substantial impact of reducing speeds across
London. Although vulnerable road users (VRUs) remained most at risk on London’s roads,
collisions involving VRUs decreased by 36% (i.e., from 453 to 290) since the introduction
of the 20 mph speed limits. Particularly encouragingly, collisions involving pedestrians
decreased by 63%.
In Bristol, UK, the implementation of 20 mph zones has resulted in a 63% reduction
in fatalities at the city level [
51
]. Similarly, in Warrington, there was a reported 43%
reduction in serious and slight pedestrian injuries compared to the 18-month period before
the experimental period [
52
]. Furthermore, in Brighton and Hove, 20 mph limits were
introduced in the city center in April 2013. In the first year of implementation, traffic speed
has dropped on 74% of roads, leading to 327 fewer casualties (
−
45%), including a 1%
reduction in fatal injuries, an 11% decrease in serious injuries, and a 33% drop in slight
injuries [53].
In 1992, Graz, Austria, was the first major European city which introduced a general
30 km/h speed limit in all city areas, aiming to improve road safety, air quality, and
reduce car reliance. Nowadays, the 30 km/h speed limit applies to nearly 80% of the
city’s road network, encompassing all residential roads, school zones, and areas adjacent to
hospitals. Already in the first two years of the policy, a 12% reduction in the number of road
crashes was identified while 20% fewer persons were seriously injured after introducing
the reduced speed limits from 50 to 30 km/h [
54
]. At the same time, road crashes involving
pedestrians and motorists also decreased by 17% and 14%, respectively [
55
]. As there were
no other policy changes related to safe transportation during the same time period, the
success could be probably attributed to the implementation of 30 km/h speed limits; but of
course, there might be other aspects which can affect safety besides policy. Interestingly,
the number of crashes began to rise again since 1996, but this was attributed to crashes
occurring on higher-level roads where speed limit restrictions did not apply. In areas with
30 km/h limits, the total number of crashes remained constant or even decreased [41].
Scotland’s biggest city, Glasgow, introduced 30 km/h speed limits at the end of 2019
in order to create safer streets and make cycling and walking more appealing options for
everyday transportation. In Glasgow, there are currently eighty-two 20 mph zones covering
288 km of roads, including the city center. Analysis of the police database revealed a total
31% reduction in the number of casualties within these zones since the implementation of
this measure [
56
]. In Berlin, Germany, the introduction of a 30 km/h speed limit in 2017
has led to a drop in crash rates by around 10% from 2017 to 2020 [57].
Previous research has examined the impact of reducing speed limits from 50 to
30 km/h on actual driving speeds [
54
,
58
–
62
]. Specifically, after the implementation of
30 km/h speed limits in Wales, United Kingdom (UK), average speeds decreased by
12.8% [
30
]. Similarly, preliminary figures from Brussels, Belgium, indicated a 7% reduction
in average speed on streets that adopted the new 30 km/h limit [
63
]. However, it was
noted that this effect increased over time. For the city of Grenoble, in France, a reduction
of 4.2 km/h in mean speeds was demonstrated, resulting in an average speed slightly
above 30 km/h [
64
]. Additionally, Hu and Cicchino [
7
] collected vehicle speed data before
and after the implementation of speed limit reductions in Boston and at control sites in
Providence, Rhode Island, where speed limits remained unchanged. They observed a
decrease in average driving speeds by 0.3%.
It should be noted that while a decrease in driving speeds was revealed, the extent of
this change can vary depending on several factors, such as the speeds driven before, the
implementation of design alterations like speed bumps, enforcement levels, the presence of
children and pedestrians on roads, and public awareness campaigns. Moreover, compliance
with reduced speed limits is typically higher when the speed limit has been reduced
Sustainability 2024,16, 4382 11 of 28
in city-wide areas compared to individual streets. Interestingly, a commonly observed
phenomenon is the “spill over effect” [
58
,
65
], where driving speeds also decrease on streets
unaffected by the speed limit reduction. This is attributed to drivers adjusting to a new
driving speed, making 50 km/h feel relatively faster after driving at 30 km/h for a period,
compared to constantly driving at 50 km/h.
Lastly, it should be clearly mentioned that according to the preliminary results, only
positive effects with regards to 30 km/h speed limits and road safety were identified. In
particular, for all reports and studies examined, speed limit reductions from 50 km/h to
30 km/h were associated with a decreased number of road crashes, fatalities, and injuries,
and no negative impact was observed.
4.2. Environment
As already mentioned, in January 2021, Brussels, Belgium, established a city-wide
30 km/h limit. Five months after the implementation, there was a reduction in traffic noise
by 2.5 db. Similarly, the introduction of 30 km/h limits in Paris, France, in August 2021,
aimed to enhance air quality and mitigate noise pollution. It was revealed that noise
pollution decreased by 3 dB following the implementation of reduced limits. Similarly, in
November 2021, Zurich’s decision to lower its speed limit was primarily driven by the goal
of reducing noise pollution. After implementing this measure, it was found that traffic
noise decreased by an average of 1.6 dB during the day and 1.7 dB at night [66].
The implementation of city-wide 30 km/h speed limits has led to reductions in noise
levels. For example, in Buxtehude, Germany, there was a reduction of 7 dB [67]. Similarly,
in Graz, Austria, noise levels decreased by 1–2 dB, while in Berlin, Germany, a reduction
of 3 dB was observed [
67
]. In Modena, Italy, noise levels decreased by 3–5 dB [
68
] and
in Sweden, low-speed zones resulted in an average noise reduction of 3–4 dB, with a
maximum reduction of 7 dB [
69
]. These findings underscore the impact that implementing
city-wide 30 km/h speed limits can have on reducing urban noise pollution, thereby
contributing to an improved quality of life for residents. It should be clearly mentioned
that the above-mentioned values refer to the average decrease in noise level (expressed
in dB) throughout the day. Additionally, where available, separate data on reductions in
traffic noise during the day and night were provided.
In order to evaluate the impact of speed limit reduction from 50 to 30 km/h on noise
and air pollutant emissions in Münster, Germany, research was conducted and data before
and after the introduction of the speed limit were utilized [
70
]. It was found that speed limit
reduction led to a reduction in road traffic noise, both metrologically and mathematically,
and the introduction of a 30 km/h speed limit had a positive effect on air pollution by
decreased nitrogen dioxide (NO
2
). In Edinburgh, UK, the speed limit on nearly all of its
roads was reduced from 30 mph to 20 mph. One year later, the areas with the reduced speed
limit experienced a reduction in particulate matter (PM) by 8% [
62
]. A similar pattern was
identified in London, where an 8–10% decrease in PM was observed, after the introduction
of 20 mph zones.
In January 2017, Berlin, Germany, implemented 30 km/h speed limit to five main
roads. Following this measure, improvements in air quality were observed. In particular,
nitrogen dioxide and monoxide emissions decreased by up to 29% from 2017 to 2020
in four out of the five cases [
41
]. Furthermore, in June 2018, Bilbao, Spain, reduced the
speed limit to 30 km/h with the aim of reducing noise and air pollution. One year later,
the city experienced reductions in air pollution; an 11.4% decrease in NO
2
-
µ
m
3
, a 17.1%
decrease in NO
X
-
µ
m
3
and a 19.1% decrease in PM
10
was identified [
40
]. Another important
finding of the impact assessment in the city of Graz, Austria, was that noise levels and NO
x
emissions dropped by 2.5 dB and 25%, respectively, when maximum speeds of 30 km/h
were introduced [54].
On the other hand, opponents of 30 km/h speed limits in cities have criticized their
efficacy with respect to air pollution (CO
2
, NO
x
, and particulate matter). Specifically, two
assumptions were made: the former refers to the emission levels when a car is driven at
Sustainability 2024,16, 4382 12 of 28
constant speeds (30 km/h versus 50 km/h), while the latter refers to the realistic driving
cycle of accelerations and decelerations (i.e., which differ with different speed limits).
Regarding the aforementioned assumptions, results from the literature revealed an increase
in emissions [
71
,
72
]. Based on these findings, 30 km/h speed limits generate more emissions
compared to 50 km/h only when the vehicle is at constant speed with no acceleration and
deceleration. In fact, a higher speed limit always means more acceleration and deceleration
in cities. Moreover, Tang et al. [
73
] examined the impact of reducing speed limits from 50 to
30 km/h. Their results showed that the emission of NO
x
and PM increased due to speed
limit reduction. However, the extent of the increase depends on the type of network and
the traffic characteristics. Moreover, Gressai et al. [
74
] provided a more nuanced analysis,
arguing that the impact of revealed speed limits on traffic can vary depending on network
topology and emphasizing the need for careful planning and analysis before implementing
speed limit reductions.
4.3. Energy
Previous studies have shown the effectiveness of 30 km/h speed limits in terms
of energy and fuel consumption. Based on the literature, lower speeds lead to lower
fuel consumption while smoother traffic flow leads to additional fuel economy, i.e., eco-
driving [
75
]. Similarly, Ahn and Rakha [
76
] investigated the environmental and energy
impacts of traffic calming measures, such as the implementation of 30 km/h speed limits
in residential areas. It was revealed that designs that require drivers to maintain a more
consistent low speed, rather than rapidly accelerating and decelerating, were not only
better for road safety but also for fuel consumption and emissions.
In a survey implemented in the Netherlands by Haworth and Symmons [
77
], it was
found that lowering speed limits and modifying driving style were found to improve fuel
economy and other environmental outcomes in addition to improving safety. In particular,
results demonstrated that with speed limit reduction, fuel consumption declined by 11%.
In addition, Litman [
78
] attempted to quantify the energy and environmental impact of
30 km/h speed limits. The results indicated that when vehicle speeds reduced speeds
from 50 km/h to 30 km/h, a 7% decrease in fuel consumption was identified. Rowland
& McLeod [
79
] revealed that decreasing maximum speed by 20% (i.e., from 50 km/h to
40 km/h), fuel consumption decreased by 3.4%. However, these effects are relatively small
and are often offset by a more continuous traffic flow (or less accelerations) and reduced car
traffic which may be due to reduced capacity and other modes being more attractive [71].
Nevertheless, it should be noted that there are a few concerns about the positive effect
of 30 km/h speed limits on fuel consumption. There are arguments often raised against
low-speed zones, that vehicles have less efficient fuel consumption at lower speeds and
can also generate more emissions, reducing air quality [
80
]. For instance, Woolley et al. [
81
]
claimed that fuel consumption may be under lower speed limits, although this result may
have been biased to some extent by the specific fuel models available in the study. This may
be due to the common understanding that traditionally, motor vehicles were designed to
maximize fuel consumption when operating at around 50 km/h. However, cities with such
speed limits typically generate patterns of harsh acceleration and braking for intersections,
turns, or traffic congestion. Research has found that this type of travel pattern is worse for
fuel consumption and emissions than traveling at a slower but more consistent operating
speed, which lowers the amount of acceleration and braking between stops.
4.4. Traffic
It should be clarified that traffic congestion is typically measured using various metrics,
including travel times and traffic volumes or traffic flow (i.e., delays in traffic). Travel times
are often monitored using GPS data, traffic sensors, or video surveillance cameras installed
along roadways, while delays in traffic can be assessed by comparing actual travel times to
expected travel times under free-flowing conditions.
Sustainability 2024,16, 4382 13 of 28
Reducing speed limits can prompt road users to choose alternative routes or modes of
transportation, which, therefore, has a great impact on traffic volumes. To begin with, in
July 2016, Edinburgh in the UK adopted a 20 mph speed limit across all residential areas.
Nightingale et al. [
62
] investigated the impact of speed reduction on traffic volume in the
city of Edinburgh. To achieve this objective, traffic data collected before and 12 months
after the phased implementation of city-wide 20 mph speed limits from 2016 to 2018
were analyzed. Results indicated an overall 5.7% reduction in average speed and a 2.4%
reduction in traffic volumes, but with the direction of effect uncertain. Additionally, the
decrease in average speeds was consistent across different days of the week and times of
the day, except during the night (01:00–06:00 am) when traffic volumes were relatively low,
possibly due to higher average speeds during that time period.
It is worth noting that in Brussels, Belgium, with the implementation of 30 km/h
speed limits, no alteration in travel times was identified [
82
]. Indeed, in some cases,
there have been traffic improvements thanks to greater traffic fluidity [
83
]. In a survey
conducted in Bilbao, responders who were initially most resistant to the measures, such
as traders, delivery drivers, and taxi drivers proved to be happy to improve traffic flow
and acknowledge that the lower speed limit did not cause them any problems [
43
]. At the
same time, with the introduction of the generalized limit throughout the city to 30 km/h,
a 2% decrease in traffic in Bilbao was also observed. With the introduction of 30 km/h
speed limits in Zurich, travel times had lengthened by between 10
00
and 30
00
seconds per
kilometer, a gap that almost disappeared during rush hour [83].
At the same time, in Grenoble, France, there was a reduction in motorized traffic in
the city between 2016 and 2018. In particular, there were 9% fewer light vehicles and 20%
fewer heavy vehicles after the introduction of 30 km/h speed limits in urban and rural
communities in Grenoble’s metropolitan area [43].
It is worth noting that travel times were found to increase between 3% and 5% [
60
]. The
aforementioned increases are usually far lower than most people intuitively assume [
24
].
This may be probably due to the fact that in dense areas, the proportion of the time that can
be driven considerably more than 30 km/h is quite low, especially during the times of day
at which most vehicle trips take place.
Like other initiatives that restrict car traffic in cities, public support increases sub-
stantially during the implementation. This is mostly because people tend to overestimate
the negative impacts, such as increased traffic congestion and longer travel times, while
underestimating the benefits of smoother traffic flow. Moreover, the positive outcomes
often only become noticeable after the measures are in place, which probably makes them
more appreciated afterwards.
4.5. Livability
Traveling by car may be discouraged due to the increase in travel time resulting from
lower speed limits. Traveling by bicycle and foot became more attractive due to the declined
crash risks, which were also observed in Brussels after the speed limit reduction [
34
]. In
addition, Copenhagen, Denmark, implemented a 30 km/h speed limit in the city center
from June 2022 to encourage the use of public transport and reduce CO
2
emissions [
84
].
However, due to the limited time since implementation, the impact of this measure has not
yet been examined.
After the introduction of 30 km/h speed limits in Zurich, Switzerland, pedestrians
and cyclists were found to be the most satisfied. In addition, many interviewees reported
feeling that the roads were safer and less noisy [
43
]. In Graz, Austria, one of the primary
goals of reducing the speed limit from 50 to 30 km/h was to decrease reliance on cars and
simultaneously encourage cycling. Results indicated that after the introduction of 30 km/h
speed limits, more than 16% of journeys were made by bike [
43
]. Interestingly, a survey
conducted in July 1992 showed that only 30% of residents were in favor of 30 km/h speed
limits before their introduction, while just 8 months later, the satisfaction rate had already
risen to 52%, reaching 81% in 2002.
Sustainability 2024,16, 4382 14 of 28
Reducing speed limits not only enhances road safety for all users but also facilitates
better utilization of public space, promoting soft and active mobility while providing
opportunities to reimagine cities. By lowering the speed limit from 50 to 30 km/h, an
average of 20 to 50 cm of roadway is freed up, which can be repurposed for various uses
such as extending sidewalks, introducing greenery, and creating cycle paths to encourage
multimodality and active travel across the French capital. Similarly, Lille became the first
city in France with over 500,000 inhabitants to gradually lower its speed limit to 30 km/h
almost everywhere, aiming to prioritize pedestrians and reduce the dominance of cars [
43
].
The main benefit after three years of implementation was a 55% increase in the number
of cyclists compared to 2016 figures [
43
]. After three years of implementation of 30 km/h
speed limits in Grenoble, France, active users approved the proposed approach and cyclists’
feelings have improved over the duration of the evaluation: 61% of pedestrians and 70% of
cyclists are in favor of the new regulations [85].
4.6. Health
With the introduction of 30 km/h speed limits in Bilbao, findings revealed that there
were fewer stressed citizens, with less health problems, and therefore, a quieter city was pro-
moted. Cycling trips increased almost sixfold, from 320,000 in 2018 (before the introduction
of the measure) to 1,791,000 in 2022 [83].
Calm driving in lower speeds is a means of promoting healthier living for drivers.
All road users, especially children and the elderly, are more likely to walk and feel more
confident in venturing outside their homes, trying to cross the street. Additionally, the
implementation of city-wide 30 km/h speed limits increases opportunities for work and
social interaction and reduces health inequalities through improved accessibility for road
users with restricted mobility, hearing, vision, or mental health, as well as children, elderly
individuals, pedestrians, cyclists, youth, and commuters [86].
Reducing speed limits in cities will provide substantial cost savings and health benefits.
Furthermore, Cleland et al. [
87
] demonstrated that the widespread implementation of
30 km/h speed limits in cities can improve the health of the public (e.g., road safety, active
travel) through reduced emissions and increased physical activity related to walking and
cycling. At the same time, Cairns et al. [
11
] revealed that 20 mile per hour speed limits
were found to be an effective means of improving public health via reduced road crashes
and injuries.
As already mentioned, the improvements resulting from reduced noise are likely
noteworthy. Findings from an interesting study conducted by Rossi et al. [
21
] revealed that
noise reduction was far more important for improvements of public health than the number
of reduced collisions. This was likely due to reduced stress levels and improved sleep,
which, among other factors, had a positive impact on the prevalence of cardiovascular
diseases and diabetes. Similarly, the effects of decreased air pollution in cases of less car
traffic could prevent a large number of years of life lost [
88
]. Lastly, Brown et al. [
89
]
indicated that if active travel modes are increased, a substantial health benefit due to more
physical activity will be provided. The overall health effects through the large decrease
in road crashes in injuries is probably relatively small when compared to the (possible)
extents of increased health due to less noise, less air pollution, and more physical activity.
5. Discussion
Setting a speed limit of 30 km/h in areas where people and traffic mix can lead to safer,
healthier, greener, and more livable streets. The reduction in speed limits aims to improve
road safety by lowering traveling speeds, thereby reducing the risk and severity of crashes.
Additionally, the introduction of 30 km/h speed limits can decrease congestion, improve
traffic flow, and reduce travel times by minimizing stop/start traffic movements. Calmer
driving at lower speeds promotes healthier living for drivers and all road users. Further-
more, implementing 30 km/h speed limits can reduce fuel consumption, emissions, and
noise. Smoother traffic flow leads to additional fuel economy, while streets that prioritize
Sustainability 2024,16, 4382 15 of 28
safe walking and cycling can reduce car dependency and harmful vehicle emissions that
contribute to climate change. The introduction of 30 km/h speed limits plays a crucial role
in reducing air pollution by decreasing carbon dioxide and nitrous oxide emissions from
diesel cars, as well as particulate matter emissions from both diesel and petrol cars. Table 2
illustrates the target goals of cities that have reduced their city-wide speed limit from 50 to
30 km/h, along with the frequency of each motivation given by the 40 cities examined.
Table 2.
The target goals of cities which have reduced their city-wide speed limit from 50 to 30 km/h.
Target Goals Cities
Less crashes, fatalities
and injuries
Amsterdam, Barcelona, Bilbao, Berlin, Bologna, Brighton, Bristol, Brussels, Den Haag, Dublin,
Edinburgh, Florence, Glasgow, Graz, Grenoble, Helsinki, Hove, Leuven, Lille, Ljubljana, London,
Lyon, Madrid, Montpellier, Munich, Münster, Paris, Stockholm, Strasbourg, Toulouse, Wales,
Warrington, Valencia, Vienna
Less air pollution
Antwerp, Berlin, Copenhagen, Graz, Leuven, Lille, Ljubljana, Madrid, Münster, Paris, Strasbourg
Less noise Amsterdam, Barcelona, Bilbao, Brussels, Edinburgh, Graz, Grenoble, Leuven, Lille, Lyon,
Münster, Paris, Strasbourg, Zürich
Less traffic congestion Amsterdam, Berlin, Copenhagen, Florence, Lille
More cycling and walking Amsterdam, Barcelona, Brighton, Bristol, Edinburgh, Florence, Glasgow, Grenoble, Hove, Lille,
London, Lyon, Madrid, Munich, Paris, Toulouse, Wales
Increased livability Amsterdam, Barcelona, Bilbao, Bologna, Brussels, Copenhagen, Edinburgh, Florence, Glasgow,
Helsinki, Ljubljana, Lyon, Montpelier, Münster, Paris, Toulouse, Wales, Warrington
More public space Amsterdam, Brighton, Bristol, Bologna, Glasgow, Grenoble, Lyon, Montpellier, Münster, Paris
Improved health Bilbao, Barcelona, Wales
The majority of cities (34 out of 40) cited increased traffic safety, leading to fewer
road crashes and less severe collisions, as the main goal of reducing speed limits. A great
percentage (35%) of cities (14 out of 40) also identified noise reduction as a reason, while
only 11 out of 40 cities proposed this measure to address air pollution, as indicated in
Table 2. Additionally, improving the usage of active or alternative transport modes was
cited by 18 out of 40 cities as a motivation, and improving the quality of public space
was mentioned by ten cities. Eighteen cities mentioned increasing livability, enhancing
the friendliness of the city, or improving the quality of life. Improved health was only
mentioned by Barcelona, Bilbao, and Wales, mainly as a consequence of reduced noise
and increased use of active transport modes. Only five cities (i.e., Amsterdam, Berlin,
Copenhagen, Florence, Lille) mentioned the reduction of car usage and traffic congestion as
a motivation, though not as the main motivation but rather as a welcomed side effect. It is
worth noting that improvement of child play or independence, as well as enhancement of
social interactions, social cohesion, or social safety, were not mentioned once as immediate
motivations.
It is apparent that most of these cities have only reduced the speed limit in the
last couple of years. By the time writing of this paper (May 2024), most cities were in
western Europe, mostly France, Belgium, and Spain. For each city, an attempt was made to
identify the motivations and ambitions. Figure 2depicts a schematic overview of the most
important—defined as being a pioneer or large—cities with 30 km/h speed limits along
with their target goals and motivations.
A comprehensive literature review was conducted to identify cities that have either
reduced or intend to reduce the speed limit to 30 km/h on the majority of their streets,
including main streets in addition to residential or side streets. Subsequently, comparisons
were made between conditions before and after the phased implementation of city-wide
30 km/h speed limits. It is important to note that since many of these cities have only
recently lowered their speed limit, the impact of implementing 30 km/h limits in several
cities has not yet been fully examined.
Sustainability 2024,16, 4382 16 of 28
Sustainability 2024, 16, x FOR PEER REVIEW 16 of 28
important—defined as being a pioneer or large—cities with 30 km/h speed limits along
with their target goals and motivations.
Figure 2. A schematic overview of the cities with 30 km/h speed limits along with their target goals.
A comprehensive literature review was conducted to identify cities that have either
reduced or intend to reduce the speed limit to 30 km/h on the majority of their streets,
including main streets in addition to residential or side streets. Subsequently,
comparisons were made between conditions before and after the phased implementation
of city-wide 30 km/h speed limits. It is important to note that since many of these cities
have only recently lowered their speed limit, the impact of implementing 30 km/h limits
in several cities has not yet been fully examined.
Table 3 presents a summary of the effectiveness of city-wide 30 km/h speed limits in
terms of safety, emissions, noise, and traffic, while Table A1 in Appendix A provides an
overview of the cities which reduced their speed limit to 30 km/h and their motivations to
do so by screening scientific papers, reports, and articles. It should be mentioned that the
numbering (i.e., from 40 to 1) in Table A refers to the total number of cities included in the
meta-analysis (i.e., from the oldest to the most recent implementation date started).
Table 3. Summary of the effectiveness of city-wide 30 km/h speed limits.
No City Safety Environment Traffic
Crashes Fatalities Injuries CO
2
, NO
x
, PM Noise Congestion
40 Amsterdam
39 Wales
38 Bologna −14.5%
37 Florence
36 Copenhagen
35 Lyon −22% −40%
34 Den Haag
33 Zurich −16% −25% −20% −1.7 dB
32 Toulouse
31 Vienna
30 Paris −40% −25% −3 dB
Figure 2.
A schematic overview of the cities with 30 km/h speed limits along with their target goals.
Table 3presents a summary of the effectiveness of city-wide 30 km/h speed limits in
terms of safety, emissions, noise, and traffic, while Table A1 in Appendix Aprovides an
overview of the cities which reduced their speed limit to 30 km/h and their motivations to
do so by screening scientific papers, reports, and articles. It should be mentioned that the
numbering (i.e., from 40 to 1) in Table A1 refers to the total number of cities included in the
meta-analysis (i.e., from the oldest to the most recent implementation date started).
Table 3. Summary of the effectiveness of city-wide 30 km/h speed limits.
No City Safety Environment Traffic
Crashes Fatalities Injuries CO2, NOx, PM Noise Congestion
40 Amsterdam
39 Wales
38 Bologna −14.5%
37 Florence
36 Copenhagen
35 Lyon −22% −40%
34 Den Haag
33 Zurich −16% −25% −20% −1.7 dB
32 Toulouse
31 Vienna
30 Paris −40% −25% −3 dB
29 Montpellier
28 Münster −72% ↓ ↓
27 Valencia
26 Leuven
25 Brussels −10% −55% −37% −2.5 dB
24 Nantes
23 Glasgow −31%
22 Antwerp
21 Barcelona
20 Lille
19 Helsinki −9% −42%
18 Madrid
17 Bilbao −28% −19% −2%
Sustainability 2024,16, 4382 17 of 28
Table 3. Cont.
No City Safety Environment Traffic
Crashes Fatalities Injuries CO2, NOx, PM Noise Congestion
16 Strasbourg
15 Dublin
14 Berlin −10% −29% −3 dB
13 London −46% −25% −25% −10%
12 Grenoble −30% −20% −50% −9%
11 Ljubljana
10 Luxembourg ↓
9 Ghent
8 Edinburgh −38% −23% −33% −8% −2.4%
7 Bristol −63%
6 Munich
5 Brighton −45%
4 Hove −45%
3 Warrington −43%
2 Stockholm
1 Graz −12% −20% −25% −2.5 dB
Gray color indicates that the impact of the implementation of 30 km/h in this city has not been examined yet. The
symbol
↓
indicates that the quantitative effect of this measure has not been provided; only qualitative impact is
given. The above reductions refer to a comparison period before and after the implementation of 30 km/h speed
limits which is not the same among all cities examined.
The range along with the average values of the quantitative effect of city-wide 30 km/h
speed limit in terms of safety (i.e., crashes, fatalities, injuries), emissions, noise, fuel con-
sumption, and traffic congestion are presented in Table 4. Notably, there was a decrease
in road crashes, with an average reduction of 23%, and a maximum reduction of 46%, as
indicated in Table 4. This reduction in crashes translates to a safer urban environment, as
evidenced by the corresponding decrease in fatalities and injuries by averages of 37% and
38%, respectively, with even more substantial reductions in certain instances. Additionally,
the implementation of lower speed limits resulted in tangible environmental benefits, in-
cluding an average decrease of 18% in emissions and reductions in noise pollution levels
by an average of 2.5 dB. Furthermore, fuel consumption decreased by an average of 7%,
indicating improved fuel efficiency and reduced environmental impact. Moreover, the
reduction of city-wide speed limits contributed to the alleviation of traffic congestion, with
an average reduction of 2%.
Table 4. Range and average values of the quantitative effect of city-wide 30 km/h speed limits.
Range Average
Crashes −[9–46%] −23%
Fatalities −[23–63%] −37%
Injuries −[20–72%] −38%
Emissions −[8–29%] −18%
Noise −[1.7 dB–3 dB] −2.5 dB
Fuel consumption −[3.4–11%] −7%
Traffic congestion +[5% up to −9%] −2%
It should be clearly mentioned that Table 4contains the range and average values
from 18 cities for which there was information available. It should be noted that each of the
40 European cities examined had different sizes and characteristics, different total length
of 30 km/h implementation area (e.g., 75% of road network, 65% of urban roads, or the
entire city center), different population sizes, and different implementation periods for
Sustainability 2024,16, 4382 18 of 28
which the assessment was made, as presented in Table A1 in Appendix A. Taking all the
aforementioned arguments into consideration, it was difficult to interpret the results within
the context of population disparities. It is still too early to draw definitive conclusions and
it is known from other cities that the trend continues more strongly over time. Thus, a
conservative approach was followed by simply presenting the average changes observed.
These findings underscore the multifaceted advantages of lower speed limits, not only
in enhancing road safety but also in promoting environmental sustainability and improving
overall urban livability. As such, policymakers and urban planners should consider the
implementation of reduced speed limits as a comprehensive strategy for creating safer,
healthier, and more efficient urban environments.
5.1. Research Gaps
The study encountered several limitations that warrant acknowledgment. Firstly, there
was a lack of data to quantitatively assess the effects of speed limit reductions on livability
and public health. Given that many of these cities have only recently implemented the speed
limit reductions, the impact of the introduction of 30 km/h speed limits in several cities
has not yet been thoroughly examined through scientific journals and papers. Importantly,
to date, there has been no comprehensive evaluation of the impact of city-wide 30 km/h
speed limits on road crashes, fatalities, and serious injuries. By the time of writing of this
paper, although the vast priority was to include peer-reviewed journals over peer-reviewed
conference papers in order to ensure the quality of this paper, there was no evidence found
in the literature; thus, scientific reports, articles, and websites were included in the meta-
analysis to support our findings. Also, it should be noted that the majority of reports and
articles included in the analysis seems valid as it includes results of 1–2 years of 30 km/h
speed limit implementation.
It is important to clarify that the results presented in this study are based on limited
and primarily anecdotal evidence gathered from various sources, including websites of
organizations and public authorities, as well as detailed reports. There is a lack of compre-
hensive data from all cities based on published papers in scientific journals. Furthermore,
the available information primarily focuses on immediate effects such as reduced speed,
road crashes, noise, and pollution.
Secondly, it is worth highlighting that due to the COVID-19 pandemic, 2020 was
not a typical year in terms of mobility and road safety. The COVID-19 pandemic had an
impact on traffic and road safety, with a reduction in road fatalities per million population
following the introduction of lockdown measures. It should be clearly mentioned that a
great part of this reduction can be attributed to the introduction of the 30 km/h speed
limits, but there are also other crucial parameters that might have led to this decrease, such
as the COVID-19 pandemic.
Thirdly, the scientific literature review revealed mixed results concerning fuel con-
sumption, energy usage, and the impact of speed limit reductions. While some studies
indicate that fuel consumption and CO
2
/NO
x
emissions might increase when a car is
driven at 30 km/h instead of 50 km/h, other research suggests otherwise. For instance, a
study by Cerema [
85
] found that more CO
2
emissions were generated when traveling at
a constant speed of 30 km/h compared to 50 km/h, highlighting the pollution generated
during frequent deceleration and acceleration typical in urban driving conditions and at
higher speeds. However, these effects were generally minor and often mitigated by factors
such as a more continuous traffic flow (resulting in fewer accelerations) and reduced car
traffic due to other modes of transport becoming more appealing [
71
]. The relationship
between speed and air quality is complex and influenced by various factors including
vehicle type, brake and tire wear, variability and consistency of driving speed, and the
nature of the road environment. Studies conducted elsewhere have yet to definitively prove
either a positive or negative effect on air quality; driving at a 30 km/h speed limit may
cause some emissions to rise slightly while others may decrease.
Sustainability 2024,16, 4382 19 of 28
Moreover, another limitation of the present collision meta-analysis was that only
several months and one or two years’ worth of post-implementation data was utilized. Even
though the key findings and the outcomes were promising and encouraging, the analysis
should be interpreted as preliminary until additional years’ data become available in order
to guarantee a more definitive and thorough evaluation. Thus, additional data collection
and evaluation are needed in order to assess these potential effects. The short-term effects
of a speed reduction may be enhanced due to novelty and enforcement; however, the
long-term effects of posted speed limit reductions could not be further determined.
It should be noted that the research findings highlighted the importance of context-
specific analysis when adjusting speed limits, taking into account factors such as local
conditions, traffic volume, and road type. Nevertheless, it is important to recognize that
the effectiveness of speed limit changes may vary depending on the specific road network,
necessitating careful planning and analysis before implementation. In addition, when
a speed limit change occurs on a specific road, it is likely to affect traffic patterns and
flow in the surrounding road network, potentially leading to changes in collision patterns.
Lastly, the impact of reduced speed limits on aspects such as livability, public space usage,
social interactions, social cohesion, life satisfaction, sense of belonging, and sense of street
ownership remains poorly studied. Also, the exact effects on mental and physical health
have not been directly measured in the existing literature. Even though many cities
analyzed listed livability, friendliness of the city, quality of life, and significance or usage of
public space as key motivations, these aspects have so far been only seldomly investigated.
Therefore, as there is a lack of research evaluating 30 km/h speed limit interventions, not
all key public health outcomes have been adequately investigated and reported, meaning
perceptions cannot be confirmed or refuted [
58
,
90
]. Consequently, this may be considered
another limitation of the study.
5.2. Suggestions for Further Research
Overall, the study demonstrated that the implementation of the new speed limit had
a positive impact on road safety, as evidenced by reductions in speeds and collisions.
However, there were areas where drivers did not comply with the speed limit, indicating
the necessity for further intervention. The findings underscored the importance of reducing
speed limits to enhance road safety and emphasized the ongoing need for monitoring
and evaluation of road conditions to inform decision-making effectively. The framework
proposed in this study could be adapted for use by other municipalities and jurisdictions
seeking to assess the effectiveness of their residential speed limit reductions.
The present work has highlighted several directions for future investigations aiming
to gain a deeper understanding of the outcomes associated with the implementation of
30 km/h speed limits in cities. It is important to gather documentation from additional cities
that have adopted similar measures, including smaller towns and cities where such speed
limits have been in effect for an extended period. Moreover, interviews with academics
and politicians, both within the case cities studied and other municipalities that have
implemented similar measures, would provide valuable insights into the decision-making
processing and administrative implementation of these initiatives.
Future research should also examine the long-term impact of the effectiveness of city-
wide 30 km/h speed limits, as the comparison period before and after the implementation
of 30 km/h speed limits was not the same. In the future, the quantitative effect of this
measure for more and more cities should be included in the analysis. Finally, the exact effect
of 30 km/h speed limits on mental and physical health should be taken into consideration.
Future studies should aim to assess the effectiveness of implementing 30 km/h speed limits
by examining a range of public health outcomes beyond the impact on average speed,
road crashes, and casualties. Moreover, researchers should explore and document any
unintended consequences to determine their effects on public and mental health, well-
being, and social and environmental inequalities. Lastly, more in-depth qualitative research
Sustainability 2024,16, 4382 20 of 28
is required in order to unpack the health equity impacts of the complex transport system
and examine behavior change patterns.
In future research, it will be essential to implement rigorous methodological ap-
proaches to address potential biases and enhance the validity of findings regarding the
impact of the 30 km/h speed limit reduction on road safety. Conducting sensitivity analyses
under various traffic scenarios and employing statistical techniques like interrupted time
series analysis to mitigate regression to the mean effects will be crucial steps. Additionally,
conducting subgroup analyses and sensitivity tests across different demographic groups,
road types, and time periods will help ensure the consistency and robustness of the findings.
These comprehensive efforts will be vital for strengthening the validity and generalizability
of conclusions regarding the effectiveness of the speed limit reduction in improving road
safety.
Further studies should also take into account the average values of quantitative effects
appropriately weighted by population size to provide a more accurate representation of
the overall effects among cities with available data. The size and characteristics of each
city should be also considered, allowing readers to interpret the results within the context
of population disparities. This transparency will ensure that our conclusions accurately
reflect the diversity of urban settings and avoid oversimplification of the data.
6. Conclusions and Recommendations
Speeding stands as the primary cause of road crashes globally, particularly within
urban settings where pedestrians, cyclists, and motorcyclists face heightened exposure
and vulnerability in the event of a collision. To mitigate this risk, road environments are
being designed to reduce vehicle speeds to 30 km/h or lower. This goal is accomplished
through the establishment of 30 km/h posted speed limits, bolstered by measures such
as speed enforcement, traffic calming strategies, and the provision of pedestrian facilities.
These efforts aim to safeguard the well-being of pedestrians, cyclists, and motorcyclists.
Concurrently, the adoption of 30 km/h speed limits is gaining momentum, serving as
inspiration for other communities and being progressively implemented in a growing
number of cities.
This research paper used an observational study aiming to critically assess the effec-
tiveness of city-wide 30 km/h speed limit in Europe. To fulfil this objective, a thorough
literature review was conducted and the benefits from 30 km/h speed limits in 40 cities
across Europe were highlighted. The work involved a comprehensive speed, collision,
emissions, energy, traffic, livability and health assessment of the roads before and after
implementing the new speed limit.
It should be noted that bias is an inherent challenge in research and an attempt was
made to mitigate its impact by transparently presenting the methods and limitations of this
study. In order to ensure that the balance between evidence and opinion was appropriately
maintained, several arguments have been included in the paper. It is important to mention
that the benefits of 30 km/h speed limits were highlighted in previous research and many
studies revealed that speed limit reductions can enhance road safety and urban livability.
This topic represents a complex and evolving area of study, and while scientific evidence
and historical examinations may have been limited, a comprehensive exploration of both
the negative and positive aspects of this issue was conducted.
The discussion and introduction of 30 km/h speed limits often encounter strong
opposition and entrenched resistance, while the voices of supporters tend to be relatively
muted and ineffective. It is evident that many people believe that 30 km/h speed limit
is pretty low for a standard. In particular, opponents of the 30 km/h speed limit in cities
argued that it would prolong travel times, diminishing overall commuting and transport
efficiency. Many contend that vehicles are not optimized for optimal performance at such
speeds, resulting in heightened fuel consumption and environmental pollution. Skepticism
surrounds the actual environmental benefits, with suggestions that slower speeds might
paradoxically increase emissions. Doubts persist regarding safety improvements, as some
Sustainability 2024,16, 4382 21 of 28
attribute the issue more to driver behavior than speed itself. Concerns also arise about
potential traffic congestion and subsequent crashes. Additionally, there’s apprehension
that lower speed limits would inconvenience car usage, integral to many lifestyles, and
resistance to altering established driving norms and habits further underpins opposition.
For instance, when the implementation of 30 km/h speed limit put into effect in Bologna,
residents expressed frustration at this new measure. A procession of cars brought traffic to
a halt on the day this measure came into force, while taxi drivers threatened to raise their
fares in order to compensate for having to drive more slowly.
However, all the above-mentioned arguments regarding the city-wide 30 km/h speed
limit might be questionable only for passenger car traffic for the parts of the cities which
are not densely populated and without real presence of pedestrians and cyclists. In fact,
claims that 30 km/h speed limit leads to increased traffic congestion and higher congestion
costs is a myth, unsupported by evidence. In urban centers, traffic flows most smoothly
at speeds of 20–30 km/h. Despite shorter following distances, this speed range facilitates
the entry of traffic from side streets, ensuring continuous flow. Examination of traffic
patterns in Switzerland revealed that 30 km/h allowed the road system to accommodate
more cars efficiently, resulting in faster overall travel times. This advantage is particularly
significant in a time-sensitive world. Moreover, lower speeds lead to improved driving
behavior, reducing environmental issues. Enforcing a general city-wide 30 km/h speed
limit is more cost-effective than introducing it gradually. While there are initial expenses,
such as adjusting traffic signals, these are outweighed by the broader costs associated with
higher speeds, making it an investment in public health. Society’s initial expenditures
will be recouped within a few years through substantial annual savings in reduced health
expenses. For example, Switzerland estimated annual savings of 180 to 200 million Swiss
Francs from implementing such measures.
Consequently, politicians and Authorities may exhibit hesitancy in implementing such
measures. Thus, the implementation of a city-wide 30 km/h speed limit requires careful
planning and consideration of various modalities. Establishing a legal framework is crucial
for implementing a city-wide speed limit. This involves reviewing and updating existing
traffic laws and regulations to reflect the new speed limit requirements. Coordination
with local transportation departments, city councils and law enforcement agencies is also
required.
In order to successfully implement 30 km/h speed limits in cities, it is essential to
launch public awareness campaigns that emphasize the safety benefits associated with the
reduced speed limit and elucidate the rationale behind its implementation, with the over-
arching goal of gaining public support. Efforts should extend beyond citizens to include
politicians, fostering a collective understanding and endorsement of large-scale interven-
tions for improved road safety. This comprehensive approach involves the launch of public
awareness initiatives through diverse channels, including media campaigns, strategically
placed road signage, informational brochures and community outreach programs. By
employing a multifaceted communication strategy, these campaigns aim not only to inform
but also to actively engage and unite society in advocating for the adoption of a 30 km/h
speed limit, creating a safer and more sustainable urban environment.
Simultaneously, promoting Public Transport and active mobility options is crucial
for reducing reliance on private vehicles. Encouraging citizens to embrace walking, cy-
cling and utilizing public transit services can contribute to a safer and more sustainable
urban environment. Investing in the improvement of public transit services, expanding
cycling infrastructure, and establishing pedestrian-friendly zones will not only make these
alternative modes of transportation more appealing but also align with broader initiatives
aimed at addressing environmental issues and reducing traffic congestion. In addition,
implementing traffic-calming measures is another vital component of creating safer road
environments. Modifications to road infrastructure, including the installation of speed
bumps, raised crosswalks, traffic circles, and narrower lanes, can reduce vehicular speed,
thereby enhancing safety for pedestrians and cyclists.
Sustainability 2024,16, 4382 22 of 28
The integration of Intelligent Transportation Systems (ITS) could also play a pivotal
role in enhancing road safety and traffic management. By synchronizing traffic signals
with actual traffic flow, congestion can be minimized, promoting a smoother and more
efficient transportation network. At the same time, monitoring and evaluation are essential
components of any successful transportation initiative. By systematically collecting data on
vehicle speeds, traffic volumes, crash statistics, and public feedback, stakeholders can gauge
the effectiveness of implemented measures. This data-driven approach enables informed
decision-making, allowing for necessary adjustments and continuous improvements over
time.
Lastly, it should be noted that collaboration with law enforcement agencies is crucial
for the enforcement of speed limits and the overall success of mobility and safety policies.
Promoting cooperation between stakeholders at various government levels facilitates the
implementation of sustainable policies. Law enforcement officers play a key role in ensuring
compliance with the speed limit, and their active involvement can be bolstered through
education and training programs. These programs should emphasize the significance
of the new speed limit and emphasize the heightened presence of traffic patrols. By
fostering understanding and collaboration between the community, government, and law
enforcement, a comprehensive approach to intelligent transportation and road safety can
be realized.
Author Contributions:
Conceptualization: G.Y.; Methodology: G.Y. and E.M.; Data Collection: E.M.;
Visualization: G.Y. and E.M.; Writing—original draft preparation: E.M.; Writing—review and editing:
G.Y. and E.M. All authors have read and agreed to the published version of the manuscript.
Funding: This research received no external funding.
Data Availability Statement: Data are contained within the article.
Conflicts of Interest:
The authors declared that they have no known competing financial interests or
personal relationships that could have appeared to influence the work reported in this paper.
Appendix A
Table A1. The target goals of cities which have reduced their city-wide speed limit to 30 km/h.
No Implementation
Started City Country Population Area with 30 km/h Target Goals Sources
40 December
2023 Amsterdam The
Netherlands 1,165,898 80% of the roads will have
30 km/h
Safety, less noise, less car usage,
more public space for other
usages, increased livability [31,32]
39 September
2023 Wales United
Kingdom 3,190,000 Wales adopts default 20 mph
speed limit
Safety, more active mobility,
increased livability, increased
mental and physical health [30]
38 July 2023 Bologna Italy 826,471 90% of the perimeter of the
most densely populated part
of the city
Safety, zero deaths on the
roads, promoting sustainable
mobility, increasing the quality
and usability of the
environment and public space
[39,91]
37 November
2022 Florence Italy 710 5 central roads
Safety (reducing crashes and
the number of fatalities),
returning public space to
pedestrians, reducing
traffic congestion
[92]
36 June 2022 Copenhagen Denmark 1,381,000 In the city center Encourage public transport
use, reduce CO2emissions [84]
35 March 2022 Lyon France 1,747,575 84% of roads
Safety, less noise, calming
traffic, public space for other
usages, more active mobility,
friendlier streets
[45,93]
34 December
2021 Den Haag The
Netherlands 709 65% of urban roads with
30 km/h Safety [32]
33 December
2021 Zurich Switzerland 1,419,621 Implementation on 40 km
of roads Noise reduction according to
legal requirements [38,41,43,66]
Sustainability 2024,16, 4382 23 of 28
Table A1. Cont.
No Implementation
Started City Country Population Area with 30 km/h Target Goals Sources
32 November 2021 Toulouse France 1,049,246 80% of the Ville Rose
road network
Safety, more room for bikes,
more active mobility,
increased livability [94]
31 September 2021 Vienna Austria 1,931,593 75% of Vienna’s road
network, mostly in
residential areas Safety [95]
30 August 2021 Paris France 11,142,303
All Paris except on the
ring road, the avenues
des Maréchaux, and
some other avenues
Safety, less noise and air
pollution, more space for
active mobility, increase
quality of public space,
encourage walking, cycling,
and use of public transport,
increased traffic flow
[36,43]
29 August 2021 Montpellier France 473,206 Some main roads
maintain 50 km/h
Safer, more fluid, more
peaceful, sharing space,
increase in well-being
(“bienveillance”),
cohabitation of different
modes, more attentiveness
to city environment
[44]
28 July 2021 Münster Germany 317,713 263 municipalities
Safety, less noise and air
pollution, more public space,
improve urban livability and
quality of life
[70]
27 May 2021 Valencia Spain 836,857 All the streets that have
only one lane in each
direction of movement
In 2021 for all Spanish cities:
align with EU/UN safety
guidelines, e.g., −50%
severe crashes
[43]
26 April 2021 Leuven Belgium 102,236 Center of Leuven Safety, air and noise
pollution [96]
25 January 2021 Brussels Belgium 1,222,000 All roads in the capital
with the exception of
the major axes
Safety, less noise, make
neighborhoods quieter
and greener [33–35,63,82,83]
24 August 2020 Nantes France 331,439 80% of the city Safety for pedestrians and
cyclists, reducing
noise pollution [46]
23 January 2020 Glasgow Scotland 1,689,000 Vast majority of city
roads Safety, more space for
active mobility [56]
22 January 2020 Antwerp Belgium 53,063 The entire city center Less air pollution [97]
21 December 2019 Barcelona Spain 5,658,472 75% of the city’s streets
Safety, less noise, more
active mobility, physical
activity, well-being,
livability, reduced effects of
climate emergency
[98]
20 August 2019 Lille France 1,073,395 88% roads
Safety, calmness, evolution
of behavior, more soft
mobility and public
transport, reduced car traffic,
less pollution and noise
[43]
19 May 2019 Helsinki Finland 685,457 2/3 of road network
Safety (Vision Zero—no
serious injuries or deaths
due to traffic), eco-friendly,
focus on children,
pedestrians, and cyclists
[41,43]
18 September 2018 Madrid Spain 6,713,557 80% of the total number
of streets and 85% of the
total length coverage
Safety, cohabitation of
different modes, air quality [99]
17 June 2018 Bilbao Spain 353,173 in 2018: 87% set 30
km/h, in September
2020: 100% set 30 km/h
Safety, CO2emissions, less
noise and thus better health,
improved quality of life
for residents
[40,43,83,100]
16 February 2017 Strasbourg France 276,170 Gradually to the
whole city Safety, less noise
and emissions [101]
15 January 2017 Dublin Ireland 1,255,963 An area between
the canals Safety [102]
14 January 2017 Berlin Germany 3,570,750 5 main roads Safety, air pollution,
traffic congestion [41,57]
13 July 2016 Edinburgh United
Kingdom 548 80% of
Edinburgh’s streets Safety, active modes,
livability and quality of life [47,48,62]
Sustainability 2024,16, 4382 24 of 28
Table A1. Cont.
No Implementation
Started City Country Population Area with 30 km/h Target Goals Sources
12 June 2016 London United
Kingdom 9,540,576 46% reduction in death
and serious
injury crashes
Safety, more walking
and cycling [50]
11 January 2016 Grenoble France 534 80% of the streets
Safety, less noise,
reinventing and calming
public space, promote
active mobility
[43,44,85]
10 September 2015 Ljubljana Slovenia 286,978 Mix of 30 km/h and
pedestrian areas
Safety, air quality, and
improve living conditions
for citizens [43]
9 August 2015 Luxembourg Luxembourg 647,599 Mostly residential areas Slower traffic and improving
quality of life for residents [42]
8 April 2015 Ghent Belgium 472 All roads with the
exception of the
major axes Slower traffic [103]
7 2015 Bristol United
Kingdom 467,099 63% city-level reduction
in road deaths
Safety, encourage more
people to walk and cycle,
create more pleasant and
shared community space
[51]
6 2011 Munich Germany 1,566,128 80% of the 2300
kilometers of
urban network
Safer for cyclists and
pedestrians, promote cycling [104]
5 2010 Brighton United
Kingdom 277,103 74% of the routes in the
city center
Safety, encourage more
active travel, provide a
calmer space for active
forms of travel
[53]
4 2010 Hove United
Kingdom 91,900 74% of the routes in the
city center Safety, minimizing serious
casualties, active travel [53]
3 July 2005 Warrington United
Kingdom 210,829 140 roads in a
residential
neighborhood
Safety, promote
public transport [52]
2 2004 Stockholm Sweden 1,656,571 On all residential streets Safety (Vision Zero—no
serious injuries or deaths
due to traffic) [43]
1 September 1992 Graz Austria 295,424 127.58 km2(80% of
roads) except
priority roads
Safety, less pollution
and noise [41,43,54,55,67–69]
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