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Do speed bumps really decrease traffic speed? An Italian experience

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Massimiliano Pau at University of Cagliari
Massimiliano Pau
Silvano Angius
Silvano Angius
Silvano Angius
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Abstract

Italy introduced the extensive use of speed bumps only in 1990, in an attempt to limit the high number of fatalities involving pedestrians in urban streets caused by the high speed of vehicles. In many countries, such devices have been the subject of careful investigations (in order to assess their effectiveness and disadvantages for the traffic circulation) and this has resulted in a number of modifications in the design to improve their performance. On the contrary, no systematic and scientific studies have been carried out on Italian installations: moreover, the type of undulation adopted is known to produce a series of problems for some categories of users and is not so effective in reducing speed as larger devices such as 'speed humps' or 'speed cushions'. This paper proposes a study of the effectiveness of 23 speed bumps installed in the city of Cagliari; to this aim, a speed analysis was performed at speed bump locations, at the crosswalks protected by the devices and at sections of the streets where bumps are installed but far from them. The results show that in one third of the cases the 85th percentile of speed measured at the speed bumps is higher than the posted speed limit (50 km/h) and an equal percentage of vehicles travel at a speed in the range of 45-50 km/h. No statistically significant differences were found from the comparison of speed values observed in free, bump or crosswalk sections of the same streets, while speed profiles calculated at four sites, where a high percentage of braking vehicles was observed, showed a common trend from which it clearly emerges that the effect of the device on driver's behaviour is restricted to a short spatial range (about 20-30 m before and after the bump). The current situation thus suggests the use of more effective devices such as humps or cushions, or the integration of speed bumps with other traffic calming techniques.
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Accident Analysis and Prevention 33 (2001) 585–597
Do speed bumps really decrease traffic speed?
An Italian experience
Massimiliano Pau *, Silvano Angius
Department of Territorial Engineering,Transportation Section,Uni!ersity of Cagliari,Piazza d
’
Armi,
09123
Cagliari,Italy
Received 2 March 2000; received in revised form 30 July 2000; accepted 31 July 2000
Abstract
Italy introduced the extensive use of speed bumps only in 1990, in an attempt to limit the high number of fatalities involving
pedestrians in urban streets caused by the high speed of vehicles. In many countries, such devices have been the subject of careful
investigations (in order to assess their effectiveness and disadvantages for the traffic circulation) and this has resulted in a number
of modifications in the design to improve their performance. On the contrary, no systematic and scientific studies have been
carried out on Italian installations: moreover, the type of undulation adopted is known to produce a series of problems for some
categories of users and is not so effective in reducing speed as larger devices such as ‘speed humps’ or ‘speed cushions’. This paper
proposes a study of the effectiveness of 23 speed bumps installed in the city of Cagliari; to this aim, a speed analysis was
performed at speed bump locations, at the crosswalks protected by the devices and at sections of the streets where bumps are
installed but far from them. The results show that in one third of the cases the 85th percentile of speed measured at the speed
bumps is higher than the posted speed limit (50 km/h) and an equal percentage of vehicles travel at a speed in the range of 45–50
km/h. No statistically significant differences were found from the comparison of speed values observed in free, bump or crosswalk
sections of the same streets, while speed profiles calculated at four sites, where a high percentage of braking vehicles was observed,
showed a common trend from which it clearly emerges that the effect of the device on driver’s behaviour is restricted to a short
spatial range (about 20–30 m before and after the bump). The current situation thus suggests the use of more effective devices
such as humps or cushions, or the integration of speed bumps with other traffic calming techniques. © 2001 Elsevier Science Ltd.
All rights reserved.
Keywords
:
Speed bumps; Pedestrian safety; Traffic calming
www.elsevier.com/locate/aap
1. Introduction, background and purposes of the study
Since early studies were carried out by the Trans-
portation Research Laboratory (UK) in the 1970s
(Watts, 1973), the use of vertical raisings of the road
pavement as a passive method for controlling the speed
of vehicles has become common in many countries
(especially in western Europe and North America).
To date, several kinds of these devices have been
designed by exploiting the same basic principles, but
with the obtaining of different results in terms of effec-
tiveness, discomfort, and dangerousness for some cate-
gories of road users; usually they are classified as:
1. Speed ‘‘bumps’’.
2. Speed ‘‘humps’’.
3. Speed ‘‘cushions’’.
The first two are characterised by a continuous verti-
cal deflection placed across the street made using sev-
eral materials (rubber, concrete, thermoplastic materials
etc.) but with a range of different dimensions. As
shown in Fig. 1, speed bumps are very short (usually
the width is between 600 and 1200 mm) with a height in
the range of 30– 100 mm (depending on the posted
speed limit) and a circular or parabolic profile, while
speed humps have about the same height values, but
are wider (from 4000 to 8000 mm) and have a variety of
different profiles (circular, sinusoidal, flat top etc.).
From the viewpoint of the effect on vehicles, speed
bumps produce impacts that are often dangerous for
the suspension system and are a source of high levels of
* Corresponding author. Tel.: +39-070-6755270; fax: +39-070-
6755261.
E-mail address
:
pau@doctorsun.unica.it (M. Pau).
0001-4575/01/$ - see front matter © 2001 Elsevier Science Ltd. All rights reserved.
PII: S0001-4575(00)00070-1
... The articles devoted to traffic calming tend to focus on the impact of humps on factors including traffic safety [19][20][21][22][23][24], ride comfort, and driving safety [25][26][27][28][29]; the condition of the pavement [25,[30][31][32]; and traffic-generated noise [33][34][35][36]. These publications address the sustainability of traffic calming designs only partially. ...
Effectiveness of a Series of Road Humps on Home Zone Streets: A Case Study
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Traffic calming measures are implemented more and more often in residential districts as part of home zone sustainability projects. For economic reasons, road humps are the most commonly used traffic calming measures to slow down the traffic within the home zone. Prefabricated units or concrete pavers are the materials of choice for their construction. The studies carried out so far on many different road hump types covered the effect of height, approach/departure ramp inclination(s), and intervals between successive humps on the final speed and the safety of road traffic. The impacts of braking before and acceleration after passing a hump on the pavement and the effect of the associated shocks on the riding comfort of both drivers and passengers and vehicle suspension were also investigated. What is missing in the available literature is information on the slowing effect of road humps depending on the longitudinal gradient of the street and the street’s landscaping. This article is intended to fill this gap by presenting the results of speed surveys carried out on three selected two-way streets located in home zones with different longitudinal gradients and a few humps of different designs that are placed at different intervals. Speeds were measured both before and after each of the successive humps. The “after” speeds were found to depend not only on the hump type and parameters but also on the direction of travel, vertical alignment of the street, parking location, and orientation of the parking space relative to the road axis.
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... Sometimes, to calibrate the theoretical models, the results of the field campaigns are taken into consideration and then compared with those derived from ad hoc experimentations [50,51]; this allows to derive the empirical speeds [52,53] and the characteristics of the vertical traffic calming device and the road [54,55]; thus, by knowing only the layout of the devices, it is possible to somehow predict the speeds without going through experimental observations [56][57][58][59], in order to reduce deaths and serious injuries [60]. ...
Towards a New Design Methodology for Vertical Traffic Calming Devices
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With increasing emphasis on new soft mobility in urban areas, it becomes more and more important to provide effective speed control measures for vehicular traffic. Among those, the ones based on vehicle vertical deflection, namely vertical traffic calming measures, are historically the most widespread. However, since the basic operating principle of these devices is related to the vertical dynamic response due to the interaction between the moving vehicle and the road profile, different vehicles may exhibit different speed behaviors when traveling on a specific road profile shape. As a matter of fact, recent research provided evidence of this connection, and therefore it has been worth investigating the dynamics underlying the phenomenon in order to develop a new approach to the design of vertical traffic calming devices. In this paper, following an initial state-of-the-art review, an in-depth study on the dynamic interaction between vehicle and road profile has been presented by means of an ad hoc-developed mathematical model. The proposed simulation model has been used to evaluate the root mean square acceleration value associated with each vehicle/traffic calming device/crossing speed. Following the outcomes provided by numerical simulations, an experimental investigation has been designed and carried out on a vertical traffic calming device. Speed profiles of different vehicles have been acquired, and preliminary results seem to provide evidence of a different dynamic response for each vehicle type, yielding the basis to reconsider the design approach of such devices in order to control urban traffic speed.
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... The findings of a current research done on 30 speed humps in an Italian city (Pau and Angius 2001) revealed that their efficiency is extremely weak. This result matches the findings of earlier works (Watts 1973;Mak 1986;Stephens 1986;Zaidel et al. 1992) demonstrating that bigger tools are better than narrow humps in decreasing velocity. ...
The effect of traffic at speed bumps in residential areas on noise and air pollution
Article
Full-text available
  • Jun 2023
  • ENVIRON SCI POLLUT R
Although transportation systems are an increasing necessity in today’s connected world, the over-reliance on internal combustion engine vehicles has caused an increase in air and noise pollution. Air and noise pollutions are among the negative environmental factors that contribute to disease occurrence due to their negative health consequences. Literature has showed that air and noise pollutions were responsible for thousands of premature deaths in Europe. This has pushed scientists to search for models to calculate the effect of traffic on air and noise pollution, to help predict future scenarios, and to work on ways to mitigate that increase in pollution. In this paper, a statistical model is done by using data measured for 25 speed bump locations in Kuwait, which included traffic flow data in the form of vehicle count and classification, as well as noise level measurements taken through an Amprobe SM20 sound meter, in addition to air pollutant data obtained from the Environment Public Authority (EPA) in Kuwait. The results of the multivariate linear regression model showed that high traffic counts resulted in significantly higher noise levels, reaching more than 70 decibels in certain locations, which is considered unhealthy for extended time periods. The model also showed that sulfur dioxide levels were impacted by both light and heavy vehicles, while particulate matter less than 10 µm was affected mainly by heavy vehicles. An online survey on speed bumps was completed by 803 participants to understand the behavior of people at speed bumps in Kuwait and understand if age and gender might be a predictor of how people would behave, and this was done by doing Pearson’s chi-squared correlation tests on the results obtained from the survey.
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... Aşırı hıza karşı kasis gibi hız kesici uygulamalar denenmektedir, ancak bunların aracın bir takım aksamına zarar vermek gibi dezavantajları olabilmektedir. Ayrıca bazı sürücüler kasisten geçtikten sonra kaybettiği hızı tekrar kazanmak için ivmelenerek gereksiz yakıt tüketimine, çevre ve gürültü kirliliğine neden olmaktadır [8,9]. Günümüzde otomatik plaka okuyan sistemler ile ortalama hız limiti ve trafik güvenliği çalışmaları, Avusturya [10], Galler dahil İngiltere [11], Hollanda [12], İtalya [13] ve İrlanda [14] gibi ülkelerde uygulanmaktadır. ...
Ortalama hız limiti uygulamasının donanımlı araçlar sayesinde alansal yaptırımı
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Full-text available
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... Aşırı hıza karşı kasis gibi hız kesici uygulamalar denenmektedir, ancak bunların aracın bir takım aksamına zarar vermek gibi dezavantajları olabilmektedir. Ayrıca bazı sürücüler kasisten geçtikten sonra kaybettiği hızı tekrar kazanmak için ivmelenerek gereksiz yakıt tüketimine, çevre ve gürültü kirliliğine neden olmaktadır [8,9]. Günümüzde otomatik plaka okuyan sistemler ile ortalama hız limiti ve trafik güvenliği çalışmaları, Avusturya [10], Galler dahil İngiltere [11], Hollanda [12], İtalya [13] ve İrlanda [14] gibi ülkelerde uygulanmaktadır. ...
View
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Investigation of Effectiveness of Traffic Calming Measures on Urban Streets under Mixed Traffic Conditions Article Info
Article
  • Oct 2021
Considering the increasing rate of fatal accidents on Indian roads (MoRTH Report, 2015), the need for considerable research aiming to reduce the conflicts is necessary. A speeding vehicle can be a menace to the other road users particularly for unsignalized intersections and the zones where motorized and non-motorized traffic interaction is high such as school proximities, residential streets etc. Static speed control devices like speed bumps and humps are one of the ways to keep vehicular speeds to a certain limit in such. Although the use of these measures becomes frequent all over the world, there are still controversies that they are not actually effective in reducing speeds. Hence, the present study aimed to evaluate the performance of the existing selected traffic calming measures such as Speed bump, speed hump, speed table and rumble strips from residential streets of Mumbai City. The speed profiles of the heavy, light commercial vehicles, cars, three wheelers and motor bikes, across the selected traffic calming measures are determined, examined and analyzed. It is observed that the speed bump has shown significant reduction in speed with 6-14kmph crossing speed. While Speed hump and speed table have recorded 25 to 30kmph. Almost over 85% of vehicles speed was reduction by 70% at the bump with respect to their approaching speed. The speed hump has recorded the highest percentage of vehicles crossing the hump above the speed limit with 55% which indicates that these are not much suitable for speed controlling measures. The road space needs to be equally used by all the road users. In areas having high vehicular densities or speeds, the road is controlled or restricted in order to provide the equal use to all road users. Also, the traffic maneuvers at any of the parts of the transportation network needs to be controlled and restricted to specific movements in order to carry out the traffic operations safely. This will also result in the reduction of overall delay at intersections and avoids the blockage and jams at most of the urban roads. One of the best ways to ensure these regulations is by physical traffic calming measures. Traffic calming measures are the physical features that forces or encourages the drivers drive at a constant speed or to slow down. II. Review A speed breaker works primarily by transferring an upward force to the traversing vehicles with greater vertical accelerations. These are generally having 50mm to 150mm with varying lengths and profiles as per the requirements. For the bump design there has been several studies out of which Sahoo P.K. (2009) studied the speed bumps to develop a computer model to simulate the geometric characteristics of the speed bumps with respect to crossing speeds of the vehicles. The steps followed by the research were to select several speed bumps with different lengths and profiles, then for particular speed bump, find the 85th percentile crossing speeds of the automobiles at that location. A similar kind of study is done by Weber Philip A. (1998) in Canada by developing a multiple regression model to find the optimal design of the speed humps by using acceleration levels and discomfort criteria, shows different results. Streets, which carry only automobile traffic were recommended to have the speed humps
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Spherical Cap Studs: A novel speed bump alternative to reduce discomfort with effective speed reduction
Article
Objective: The aim of this study is to assess the potential of spherical Cap Studs (SCS) as a substitute for conventional speed bumps, with a focus on limiting two wheeler speed while minimizing discomfort to riders by comparing the speed reduction capabilities and discomfort levels associated with SCS and speed bumps. Methods: The study uses experimental approach to compare the speed limiting ability and discomfort caused to rider by the proposed SCS and a standard speed bump. Speed profiles were developed for two wheelers passing over both SCS and speed bump. The parameter employed to compare speed profiles is the Mean Absolute Percentage Difference (MAPD), offering valuable insights into how effectively the two traffic calming measures reduce two wheeler speeds. To compare discomfort, the study calculates the ‘Vibration Dose Value’ (VDV) experienced by riders when traversing both speed bump and SCS. Additionally, ‘Static Compressive Stress’ (Se) applied to the spinal cord is also calculated in both scenarios. Results: The analysis of speed profiles reveals an MAPD value of 13.70% indicating that SCS exhibits speed reduction capabilities comparable to traditional speed bump. In terms of discomfort, the VDV for two wheelers passing over a speed bump is measured at 5.92 m/s1.75, whereas the VDV for SCS is found to be 5.16 m/s1.75. Similarly, the Static Compressive Stress (Se) experienced at a speed bump is 0.60 MPa, in contrast to the 0.33 MPa recorded for SCS. This data underscores a noteworthy 12.8% reduction in VDV and a substantial 45.57% reduction in Se. Conclusion: The study’s findings support the potential adoption of SCS as an effective alternative to conventional speed bumps for controlling two wheeler speeds. SCS demonstrate a speed reduction capability similar to that of traditional speed bumps while significantly alleviating discomfort for riders. SCS is expected to be a promising solution for traffic calming purposes in various settings, such as markets, residential areas, institutional campuses, and parking lots.
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A review of the best practice in traffic calming evaluation
Article
  • May 2023
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Traffic calming (TC) has been applied widely for several decades, although approaches to evaluating its effects on speeds have been inconsistent. This resulted in limited comparable and robust evidence to support practitioner guidance for TC design. To fill this gap and suggest best practices for the evaluation of TC effects on speeds, we performed a systematic review of 158 publications. We distilled information related to five research questions: Which measurement sensor was used? How was speed measured? Was free-flow speed considered? What was the sampling density? How were sample considerations reported? In addition to coding the studies based on these research questions, we rated them based on scientific robustness. The review confirmed the inconsistent state of evaluation practice. Most common evaluation approaches employed static detectors, low levels of control for bias (simple before-after), and unknown survey periods. The review found that the most robust evaluation practices involved multivariate before-after or cross-sectional study designs, used dynamic measurement of speeds (e.g., probe vehicles, simulations), large samples of vehicles, and more precise evaluation of speed changes using speed-distance graphs. These findings could guide more consistent and robust evaluation practice, and thus help to improve evidence-based TC guidance for creating safer and more sustainable neighborhoods.
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Road humps for the control of vehicle speeds
Technical Report
Full-text available
  • Jan 1973
The suitability and effectiveness of humps for alerting drivers and controlling vehicle speeds have been investigated. Seven vehicles including private cars, goods vehicles, a moped and a bus were used in the tests and six subjects made estimates of the noticeability and discomfort of the different humps at various crossing speeds. Two main classes of hump have been studied, short humps which coild be straddled by the wheels of most vehicles and long humps which could be straddled only by some large vehicles. The humps ranged from 2 in to 12 ft (0.05m to 3.66m) in length and from 0.5 in to 6 in (i3mm to 152mm) in height. A hump 6 in (152mm) long with a height between 0.75 and 1.5 in (19 and 38mm) was capable of alerting drivers by producing a noticeable vibration. Increasing the height of short humps introduced safety problems such as the risk of loss of control or of vehicle damage by grounding and increased the severity of impact on the tyres and vehicle suspension. Increasing the length
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A model of speed profiles for traffic calmed roads
Article
Full-text available
  • Feb 2000
  • TRANSPORT RES A-POL
The influence of traffic calming measures on the speed of unimpeded vehicles has been investigated by evaluating differences in speed profiles obtained from various combinations of traffic calming measures. A case study has been conducted in the City of York (UK) focusing on traffic calming measures such as speed humps (flat-topped and round topped), speed cushions and chicanes implemented in sequence. Vehicles' passing times were simultaneously recorded at 16 points along each traffic calmed link. From these data a speed profile for each individual vehicle could be derived. An empirical model was developed using multiple regression analysis techniques based on data collected at three calibration sites. Speeds along these links were described as a function of the input speed, the type of measure and the distance between measures. The speed profile model was shown to be a good representation for the data from the calibration sites. It efficiently predicted speeds of unimpeded vehicles over a given combination of traffic calming measures in sequence. The validation process, based on data collected at three validation sites, also indicated that the model provided a good representation of the observed profiles at these sites, with the exception of the prediction of the effects of the chicanes on speeds. This type of measure was shown to produce diverse impacts on speeds which depended on the detailed design. While the model is a useful design tool, recommendations have been made for further enhancement to it.
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ROAD HUMPS FOR THE CONTROL OF VEHICULAR SPEEDS AND TRAFFIC FLOW.
Article
  • Dec 1986
Road humps, sometimes referred to as undulations or speed humps, are protuberances constructed in the roadway to reduce vehicular speed. They have a unique set of design specifications that distinguish them from the more conventional road bump. Road humps, an arc approximately 12 ft (3. 7 m) long and 3 to 4 in (76. 2 to 101. 6 mm) high, have been designed for use on residential streets that have speed limits of 25 mi/h (40 km/h) or less. In contrast, a road bump typically is an arc between 0. 5 and 3. 0 ft (0. 15 and 0. 9 m) long and 2 to 6 in (50. 8 to 152. 4 mm) high and is used in parking lots, on private roads, and on some residential streets. This article discusses the purpose and development of road humps, the effectiveness of road humps relevant to safety issues, signing and marking requirements, the benefits and problems of road humps, and other considerations. The article concludes with an assessment by city engineers, planners, and local highway administrators of the feasibility of establishing regulations and legislation on the road hump as a traffic control device.
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An experiment with road humps
Article
  • Nov 1991
In 1988 a system of road humps was provided by the City of Wakefield MDC on Chidswell Lane, Gawthorpe in accordance with the Road Hump Regulations 1983 to reduce traffic speeds and deter unnecessary traffic from using the road. Although these humps were successful it was considered that a different type/style of hump would achieve the same result at a lower cost. Following trials off the highways with various vehicles, a series of new 'mini-humps' formed in thermoplastic was laid on Manygates Lane, Wakefield in April 1990, a road that had a similar problem to that previously experienced on Chidswell Lane. The paper explains the reasons for the 'mini-hump' and its design, the trials with various vehicles and the before and after results of the Manygates Lane experiment.
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FURTHER NOTE ON UNDULATION AS A SPEED CONTROL DEVICE.
Article
  • Jan 1986
Conventional speed bumps have sometimes been used as a passive means of controlling speed, but there are problems associated with them, such as damaging the suspension and front-end alignment of crossing vehicles and causing loss of control for drives of two-wheeled vehicles under certain circumstances. The U. K. Transport and Road Research Laboratory (TRRL) developed a new speed control device known as an undulation (or speed hump) that eliminates many of the deficiencies associated with conventional speed bumps. This new design has been gaining acceptance in the United States; it has been installed in a number of cities and the results so far have been favorable.
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Speed (Road) Bumps: Issues and Opinions
Article
  • Jul 1985
Speed (road) bumps are controversial. Despite their effectiveness as a speed deterrent device, the use has not been widespread in the United States. A majority of traffic professionals are strongly opposed to the use of these bumps on public right-of-way. Liability and safety remain the primary concerns. The current trend is to use “humps” instead of “bumps” which are flatter.
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Dynamic considerations of speed control humps
Article
  • Aug 1982
  • TRANSPORT RES B-METH
The objective of this study is to investigate the effects of hump parameters (cross section, dimensions, spacing, etc.) on the dynamic behaviour of the vehicle and the driver. Vehicle safety and driver comfort are most important in evaluating the effectiveness of speed control humps. A mathematical model representing the vehicle and the driver is developed. Several hump profiles are tried. A "basic" hump is selected and the effects of the individual parameters of the hump on the dynamic response of the system are evaluated through the computer simulation. The results are analysed, conclusions and recommendations for the design of speed control humps are specified.
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Safety effects of 30 Km/H zones in The Netherlands
Article
  • Mar 1992
  • ACCIDENT ANAL PREV
Since 1983, Dutch municipal authorities can institute a maximum speed of 30 km/h on roads or in zones within built-up areas. The safety effects of 30 km/h zones are supposed to be positive. In order to be sure about this, the Ministry of Transport has stimulated 15 municipalities to implement a 30 km/h zone and set up an evaluation of the safety effects of these zones. The evaluation research is coordinated by the Institute for Road Safety Research (SWOV). The evaluation concerns the changes in traffic flows, opinions of residents, conflicts, and accidents. This paper gives the results of the evaluation.
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The use of road humps for moderating speeds on Urban streets
Article
  • Mar 1992
  • ACCIDENT ANAL PREV
Road humps are devices placed in the path of traveling vehicles. They are used in many communities to keep a uniform and low speed on a residential street or to reduce speeds at specific locations, such as intersections or pedestrian crosswalks. While the effectiveness of road humps in moderating speeds at the site of installation is generally considered proven, the actual adoption of the device remains controversial at the level of the community and the practicing engineers. The present paper, based on literature review and an international survey, evaluates community acceptance of the device and the factors influencing it; describes the various approaches taken to solve problems such as accommodating public transport and emergency vehicles; and assesses the legal status of the device.
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Safety effects of speed reducing measures in Danish residential areas
Article
  • Mar 1992
  • ACCIDENT ANAL PREV
On May 1, 1977 a new code was introduced into the Danish Road Traffic Act. The result was a change in layout and speed limits in a great number of residential streets; in most cases the streets were transformed into 30 km/h streets and in few cases into 15 km/h streets. In addition to speed signs, both types of streets were equipped with speed reducing measures. Based on experiences from a selection of experimental streets, mostly 30 km/h streets, different, but very positive effects were found. Overall there was a reduction in the mean speed in these areas of 11 km/h. On the 223 km, 30 km/h streets there was a reduction of 77 accidents and 88 casualties within a period of three years. These reductions were caused by the implementation of speed signs, speed reducing measures, and a reduction in traffic. On the basis of 44 experimental streets, where traffic was recorded both before and after the changes, the reduction in risk of casualties, i.e. the number of casualties per road user km, was 72%, while the risk of accidents seemed to be unchanged. Considering serious injuries alone, a very high reduction of 78% was found. Accidents included in the study consist of all police reported accidents, i.e. accidents with personal injury as well as damage only accidents.
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