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This study aimed to evaluate the impact of the roll-out of 20mph speed limits across the city of Bristol. The research took a holistic, public health approach to evaluation, using a variety of data sources to examine changes in vehicle speeds, road traffic casualties, levels of walking and cycling, public perceptions and attitudes, and reported levels of health and wellbeing across the city. The study found statistically significant reductions in average traffic speeds of 2.7mph across the city of Bristol, following the introduction of 20mph speed limits. This is a larger reduction than seen in previous evaluations in other cities. The study employed a more sophisticated analysis than previous studies of 20mph limits, including using individual speed data from over 36 million vehicle observations and controlling for other factors that might affect changes in traffic speeds. There has been a reduction in the number of fatal, serious and slight injuries from road traffic collisions, equating to estimated cost savings of over £15 million per year. Although there is still majority support for 20mph speed limits in Bristol, there remains concern about compliance and behaviour of other drivers. Walking and cycling across Bristol has increased, both among children travelling to school and adults travelling to work. The introduction of 20mph speed limits in Bristol offers a model for other towns and cities across the UK, who are seeking to reduce traffic speeds, cut road traffic casualties, and promote community health and wellbeing through road danger reduction. In order to assess effectiveness of 20mph speed limits, it is vital that other towns and cities follow Bristol’s example, and prioritise the ongoing collection and analysis of appropriate data on vehicle speeds, road traffic casualties and wider public health impacts.
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... Included studies were all European and published 1990-2018: UK (6); Demark (2); the Netherlands (1); Germany (1); and Poland (1). Four additional reports were found in the grey literature (Manchester City Council, 2017;Pilkington et al., 2018; The City of Edinburgh Council, 2013; Department for Transport, 2010). These were not included within the review but reported findings that warranted review were noted. ...
... Additional grey literature was found for before and after evaluations of 20 mph speed 'limits'. These interventions were implemented in Manchester (Manchester City Council, 2017), Bristol (Pilkington et al., 2018), Edinburgh (The City of Edinburgh Council, 2013) and Portsmouth (Department for Transport, 2010). The studies were not included within the main body of the current review as they did not include a control group; however, it was felt that it would be beneficial to highlight their findings. ...
... In Bristol comparison data for speed but not for public health outcomes was presented (which could not be included within the main body of the review); found speed reduced significantly by 0.8-2.7mph dependent on the measurement method (controlled) (Pilkington et al., 2018). In addition, casualties reduced, fewer residents were disturbed by traffic noise and walking to work increased 17.5-18.9%. ...
Background Road traffic injuries are a leading cause of preventable death globally, but can be reduced by introducing speed lowering interventions such as 20 mph or 30 km/h speed ‘zones’ and ‘limits’. ‘Zones’ utilise physical traffic calming measures and ‘limits’ only utilise signage and lines. Transport is a social determinant of health and therefore such interventions may in/directly also impact on other health outcomes. Aim To investigate the effect of 20 mph speed ‘zones’ and ‘limits’ on a range of health outcomes, and to establish if there are differences in the effectiveness of 20 mph zones and 20 mph limits. Methods MEDLINE, EMBASE, Web of Science and Transport Research Information Service (TRIS) databases were searched [1983–January 2019) to identify relevant studies. Reference lists, relevant systematic reviews and the grey literature were also searched. Inclusion criteria: 20 mph ‘zone’ or ‘limit’ interventions: and public health outcomes (collisions, casualties, mode of transport, noise pollution, air quality, inequalities and liveability (e.g. physical activity and perceptions of safety)) and including a control/comparison group. Results Eleven studies were identified reporting nine 20 mph ‘zone’ and two 20 mph ‘limit’ interventions. 20 mph ‘zones’ were associated with a reduction in the number and severity of collisions and casualties; have less robust evidence of the effect on air pollution; and have the potential to indirectly impact physical activity and liveability through various mechanisms for change (although currently the evidence is lacking and requires further work). No significant associations were reported between 20 mph ‘limits’ and any public health outcome. Conclusion This review suggests 20 mph ‘zones’ are effective in reducing collisions and casualties. However, it provides insufficient evidence to draw conclusions on the effect of 20 mph ‘zones’ on pollution, inequalities or liveability. For 20 mph ‘limits’ more rigorous evaluations are required in order to draw robust conclusions.
... All four evaluations reported reductions in average speed due to 20mph limits implementation. Reductions varied between Manchester (0.7mph reduction) [18], Bristol (2.7mph reduction) [19], Edinburgh (pilot scheme) (1.9mph reduction) [12], and Portsmouth (1.3mph reduction), with the Edinburgh pilot scheme and Portsmouth reporting greater reductions on roads with higher baseline speeds [20]. In a recent evaluation of twelve case study schemes in England, Atkins and Maher (2018) reported that median speeds had fallen by 0.7mph in residential areas and 0.9mph in city centre areas [21]. ...
... Some variation in the size of reduction is to be expected due to differences in context and study design. For example, the greater magnitude of reduction in Bristol (2.7mph) might be explained by higher baseline speeds (27.1mph compared to 23.6mph in Edinburgh), the longer implementation/study period (2-3 years compared to 12 months), and differences in data collection and analysis (quasi-stepped wedge design and reported an adjusted reduction compared to unadjusted pre-post analysis) [19,24]. In addition, the Edinburgh intervention increased coverage from 50% to 80% of streets [10,11] and intervention effects may have been larger if initial coverage had been lower. ...
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Objectives Traffic speed is important to public health as it is a major contributory factor to collision risk and casualty severity. 20mph (32km/h) speed limit interventions are an increasingly common approach to address this transport and health challenge, but a more developed evidence base is needed to understand their effects. This study describes the changes in traffic speed and traffic volume in the City of Edinburgh, pre- and 12 months post-implementation of phased city-wide 20mph speed limits from 2016–2018. Methods The City of Edinburgh Council collected speed and volume data across one full week (24 hours a day) pre- and post-20mph speed limits for 66 streets. The pre- and post-speed limit intervention data were compared using measures of central tendency, dispersion, and basic t-tests. The changes were assessed at different aggregations and evaluated for statistical significance (alpha = 0.05). A mixed effects model was used to model speed reduction, in the presence of key variables such as baseline traffic speed and time of day. Results City-wide, a statistically significant reduction in mean speed of 1.34mph (95% CI 0.95 to 1.72) was observed at 12 months post-implementation, representing a 5.7% reduction. Reductions in speed were observed throughout the day and across the week, and larger reductions in speed were observed on roads with higher initial speeds. Mean 7-day volume of traffic was found to be lower by 86 vehicles (95% CI: -112 to 286) representing a reduction of 2.4% across the city of Edinburgh (p = 0.39) but with the direction of effect uncertain. Conclusions The implementation of the city-wide 20mph speed limit intervention was associated with meaningful reductions in traffic speeds but not volume. The reduction observed in road traffic speed may act as a mechanism to lessen the frequency and severity of collisions and casualties, increase road safety, and improve liveability.
... Reducing speed limits on urban residential roads was found to have * considerable effects on reducing total, property-damage-only, and severe crashes (Islam & El-Basyouny, 2015) and on fatal, serious-injury, and slight-injury crashes (Pilkington et al., 2018). Similar contentions were made by Ritchey and Nicholson-Crotty (2011). ...
... With more than one million individuals dying each year on the road [1], reducing road casualties is a public health priority. Twenty miles per hour (20mph) speed limit policies (equivalent to roughly 30kmh) have become a part of public health policies to reduce urban road collisions and casualties, especially in Western countries [2,3]. Twenty mph limits are predominantly sign-based measures to reduce motor vehicle speed and are mainly used in residential areas. ...
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Background Twenty miles per hour (20mph) speed limits (equivalent to roughly 30kmh) have become part of public health policies to reduce urban road collisions and casualties, especially in Western countries. Public opinion plays a crucial role in opposition to and acceptance of policies that are advocated for improving public health. Twenty miles per hour speed limit policies were implemented in Edinburgh and Belfast from 2016 to 2018. In this paper, we extract public opinion and sentiments expressed about the new 20mph speed limits in those cities using publicly available Twitter data. Methods We analysed public sentiments from Twitter data and classified the public comments in plain English into the categories ‘positive’, ‘neutral’, and ‘negative’. We also explored the frequency and sources of the tweets. Results The total volume of tweets was higher for Edinburgh than for Belfast, but the volume of tweets followed a similar pattern, peaking around 2016, which is when the schemes were implemented. Overall, the tone of the tweets was positive or neutral towards the implementation of the speed limit policies. This finding was surprising as there is a perception among policymakers that there would have been public backlash against these sorts of policy changes. The commonly used hashtags focused largely on road safety and other potential benefits, for example to air pollution. Conclusions Overall, public attitudes towards the policies were positive, thus policymakers should be less anxious about potential public backlash when considering the scale-up of 20mph speed restrictions.
... The existing evidence shows that 30 km/h speed limits are effective in reducing road traffic crashes and casualties (Cairns et al., 2015;Grundy et al., 2009). More recently, there is a growing interest in introducing city-or town-wide 30 km/h speed limits (Pilkington et al., 2018) to improve population health and well-being. Less information exists regarding the potential benefits of speed limit reductions in terms of other health pathways, such as noise and air pollution exposures and physical activity patterns (Joffe and Mindell, 2002). ...
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Reductions of speed limits for road traffic are effective in reducing casualties, and are also increasingly promoted as an effective way to reduce noise exposure. The aim of this study was to estimate the health benefits of the implementation of 30 km/h speed limits in the city of Lausanne (136′077 inhabitants) under different scenarios addressing exposure to noise and road crashes. The study followed a standard methodology for quantitative health impact assessments to derive the number of attributable cases in relation to relevant outcomes. We compared a reference scenario (without any 30 km/h speed limits) to the current situation with partial speed limits and additional scenarios with further implementation of 30 km/h speed limits, including a whole city scenario. Compared to the reference scenario, noise reduction due to the current speed limit situation was estimated to annually prevent 1 cardiovascular death, 72 hospital admissions from cardiovascular disease, 17 incident diabetes cases, 1′127 individuals being highly annoyed and 918 individuals reporting sleep disturbances from noise. Health benefits from a reduction in road traffic crashes were less pronounced (1 severe injury and 4 minor injuries). The whole city speed reduction scenario more than doubled the annual benefits, and was the only scenario that contributed to a reduction in mortality from road traffic crashes (one death per two years). Implementing 30 km/h speed limits in a city yields health benefits due to reduction in road traffic crashes and noise exposure. We found that the benefit from noise reduction was more relevant than safety benefits.
... Research of lowering speed limits in urban areas to 50 km/hour (31 mph) in Australia, to 40 km/hour (25 mph) in Canada and to 32 km/ hour (20 mph) in the UK has found reductions in speeds and crashes, especially crashes with severe and fatal injuries, associated with lowered speed limits. [8][9][10][11][12] In the USA, although there has been a trend towards raising speed limits on interstates and freeways, which has been found to increase speeds and fatality rates, [13][14][15] some cities concerned about recent increases in pedestrian deaths have initiated efforts to improve safety for all road users. As part of these efforts, cities such as Boston, New York City and Seattle have lowered their default speed limits recently. ...
Introduction Effective 9 January 2017, the default speed limit on Boston streets was reduced from 30 mph to 25 mph. This study evaluated the effects of the speed limit reduction on speeds in Boston. Method Vehicle speeds were collected at sites in Boston where the speed limit was lowered, and at control sites in Providence, Rhode Island, where the speed limit remained unchanged, before and after the speed limit change in Boston. A log-linear regression model estimated the change in vehicle speeds associated with the speed limit reduction. Separate logistic regression models estimated changes in the odds of vehicles exceeding 25 mph, 30 mph and 35 mph associated with the lower speed limit. Results The speed limit reduction was associated with a 0.3 % reduction in mean speeds (p=0.065), and reductions of 2.9%, 8.5% and 29.3 % in the odds of vehicles exceeding 25 mph, 30 mph and 35 mph, respectively. All these reductions were statistically significant. Conclusions Local communities should consider lowering speed limits to reduce speeds and improve safety for all road users. The current practice of setting speed limits according to the 85th percentile free-flow speeds, without consideration of other characteristics of the roadway, can be a hurdle for local communities looking to lower speed limits. Updated state laws that allow municipalities to set lower speed limits on urban streets without requiring costly engineering studies can provide flexibility to municipalities to set speed limits that are safe for all road users.
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Twenty miles per hour (32 km/hour) or 30 km/hour speed limits represent a potential strategy to reduce urban road injuries and are becoming increasingly widespread. However, no study has conducted a robust evaluation of the effects of city-wide 20 mph speed limits on road injuries. This study reports the effects of such an intervention, based on a natural experiment that took place in Bristol, UK. Based on a stepped-wedge design using count data, negative binomial regressions showed that between 2008 and 2016, the 20 mph speed limit intervention was associated with a city-level reduction of fatal injuries of around 63% (95% CI 2% to 86%), controlling for trends over time and areas. There was also a general trend of reduction of the total number of injuries at city level and in 20 mph roads. These findings highlight the potential benefits of city-wide 20 mph speed limits. We hypothesise that this city-wide approach may encourage a general behaviour change in drivers that, in turn, may contribute to reducing injuries across the city.
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Background: Transport is an important determinant of health and there is a well-established association between socio-economic status (SES) and risk of road accidents. Effective traffic calming interventions such as 20 mph zones and limits may therefore improve health and reduce health inequalities. Methods: Systematic review methodology was used to identify systematic reviews of the effects of 20 mph zones (including speed limits and road humps) and 20 mph limits on health and SES inequalities in health amongst adults and children. Results: Five systematic reviews were included. Overall, they provide convincing evidence that these measures are effective in reducing accidents and injuries, traffic speed and volume, as well as improving perceptions of safety in two of the studies. There was also evidence that such interventions are potentially cost-effective. There was no evidence of the effects on SES inequalities in these outcomes. Conclusion: Twenty mile per hour zones and limits are effective means of improving public health via reduced accidents and injuries. Whilst there was no direct evidence on the effects of interventions on health inequalities, targeting such interventions in deprived areas may be beneficial. Further controlled evaluations that specifically examine SES effects are required.
Knowledge of the amount of violence tolerated by the human body is essential when developing and implementing pedestrian safety strategies. When estimating the potential benefits of new countermeasures, the pedestrian fatality risk as a function of impact speed is of particular importance. Although this function has been analysed previously, we state that a proper understanding does not exist. Based on the largest in-depth, pedestrian accident study undertaken to date, we derive an improved risk function for adult pedestrians hit by the front of passenger cars. Our results show far lower fatality risks than generally reported in the traffic safety literature. This discrepancy is primarily explained by sample bias towards severe injury accidents in earlier studies. Nevertheless, a strong dependence on impact speed is found, with the fatality risk at 50 km/h being more than twice as high as the risk at 40 km/h and more than five times higher than the risk at 30 km/h. Our findings should have important implications for the development of pedestrian accident countermeasures worldwide. In particular, the scope of future pedestrian safety policies and research should be broadened to include accidents with impact speeds exceeding 50 km/h.
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