The impact of 20 mph traffic speed zones on inequalities in road casualties in London

Effectiveness of road safety interventions: An evidence and gap map

Background

Road Traffic injuries (RTI) are among the top ten leading causes of death in the world resulting in 1.35 million deaths every year, about 93% of which occur in low- and middle-income countries (LMICs). Despite several global resolutions to reduce traffic injuries, they have continued to grow in many countries. Many high-income countries have successfully reduced RTI by using a public health approach and implementing evidence-based interventions. As many LMICs develop their highway infrastructure, adopting a similar scientific approach towards road safety is crucial. The evidence also needs to be evaluated to assess external validity because measures that have worked in high-income countries may not translate equally well to other contexts. An evidence gap map for RTI is the first step towards understanding what evidence is available, from where, and the key gaps in knowledge.

Objectives

The objective of this evidence gap map (EGM) is to identify existing evidence from all effectiveness studies and systematic reviews related to road safety interventions. In addition, the EGM identifies gaps in evidence where new primary studies and systematic reviews could add value. This will help direct future research and discussions based on systematic evidence towards the approaches and interventions which are most effective in the road safety sector. This could enable the generation of evidence for informing policy at global, regional or national levels.

Search Methods

The EGM includes systematic reviews and impact evaluations assessing the effect of interventions for RTI reported in academic databases, organization websites, and grey literature sources. The studies were searched up to December 2019.

Selection Criteria

The interventions were divided into five broad categories: (a) human factors (e.g., enforcement or road user education), (b) road design, infrastructure and traffic control, (c) legal and institutional framework, (d) post-crash pre-hospital care, and (e) vehicle factors (except car design for occupant protection) and protective devices. Included studies reported two primary outcomes: fatal crashes and non-fatal injury crashes; and four intermediate outcomes: change in use of seat belts, change in use of helmets, change in speed, and change in alcohol/drug use. Studies were excluded if they did not report injury or fatality as one of the outcomes.

Data Collection and Analysis

The EGM is presented in the form of a matrix with two primary dimensions: interventions (rows) and outcomes (columns). Additional dimensions are country income groups, region, quality level for systematic reviews, type of study design used (e.g., case-control), type of road user studied (e.g., pedestrian, cyclists), age groups, and road type. The EGM is available online where the matrix of interventions and outcomes can be filtered by one or more dimensions. The webpage includes a bibliography of the selected studies and titles and abstracts available for preview. Quality appraisal for systematic reviews was conducted using a critical appraisal tool for systematic reviews, AMSTAR 2.

Main Results

The EGM identified 1859 studies of which 322 were systematic reviews, 7 were protocol studies and 1530 were impact evaluations. Some studies included more than one intervention, outcome, study method, or study region. The studies were distributed among intervention categories as: human factors (n = 771), road design, infrastructure and traffic control (n = 661), legal and institutional framework (n = 424), post-crash pre-hospital care (n = 118) and vehicle factors and protective devices (n = 111). Fatal crashes as outcomes were reported in 1414 records and non-fatal injury crashes in 1252 records. Among the four intermediate outcomes, speed was most commonly reported (n = 298) followed by alcohol (n = 206), use of seatbelts (n = 167), and use of helmets (n = 66). Ninety-six percent of the studies were reported from high-income countries (HIC), 4.5% from upper-middle-income countries, and only 1.4% from lower-middle and low-income countries. There were 25 systematic reviews of high quality, 4 of moderate quality, and 293 of low quality.

Authors' Conclusions

The EGM shows that the distribution of available road safety evidence is skewed across the world. A vast majority of the literature is from HICs. In contrast, only a small fraction of the literature reports on the many LMICs that are fast expanding their road infrastructure, experiencing rapid changes in traffic patterns, and witnessing growth in road injuries. This bias in literature explains why many interventions that are of high importance in the context of LMICs remain poorly studied. Besides, many interventions that have been tested only in HICs may not work equally effectively in LMICs. Another important finding was that a large majority of systematic reviews are of low quality. The scarcity of evidence on many important interventions and lack of good quality evidence-synthesis have significant implications for future road safety research and practice in LMICs. The EGM presented here will help identify priority areas for researchers, while directing practitioners and policy makers towards proven interventions.

Developing and implementing 20-mph speed limits in Edinburgh and Belfast: mixed-methods study

Background

Transport initiatives such as 20-mph (≈30-km/h) speed limits are anticipated to result in fewer road casualties and improve perceptions of safety, leading to increases in active travel. Lower speeds may also lead to more pleasant environments in which to live, work and play.

Objectives

The main objective was to evaluate and understand the processes and effects of developing and implementing 20-mph speed limits in Edinburgh and Belfast. The focus was on health-related outcomes (casualties and active travel) that may lead to public health improvements. An additional objective was to investigate the political and policy factors (conditions) that led to the decision to introduce the new speed limits.

Design

This was a mixed-methods study that comprised an outcome, process, policy and economic evaluation of two natural experiments.

Setting

The study was set in Edinburgh, Scotland, and Belfast, Northern Ireland, from 2000 to 2018.

Participants

The whole population of each city were participants, as well as stakeholders involved in implementation and decision-making processes.

Intervention

The intervention was the implementation of 20-mph legislation, signage, enforcement, and education and awareness-raising in Edinburgh (citywide) and Belfast (city centre).

Main outcome measures

The main outcomes measured were speed; number, type and severity of road collisions; perceptions; and liveability.

Data sources

The following data sources were used – routinely and locally collected quantitative data for speed, volume of traffic, casualties and collisions, and costs; documents and print media; surveys; interviews and focus groups; and Google Street View (Google Inc., Mountain View, CA, USA).

Results

Collisions and casualties – the overall percentage reduction in casualty rates was 39% (the overall percentage reduction in collision rates was 40%) in Edinburgh. The percentage reduction for each level of severity was 23% for fatal casualties, 33% for serious casualties and 37% for minor casualties. In Belfast there was a 2% reduction in casualties, reflecting differences in the size, reach and implementation of the two schemes. Perceptions – in Edinburgh there was an increase in two factors (support for 20 mph and rule-following after implementation) supported by the qualitative data. Liveability – for both cities, there was a small statistical increase in liveability. Speed – mean and median speeds reduced by 1.34 mph and 0.47 mph, respectively, at 12 months in Edinburgh, with no statistically significant changes in Belfast. History, political context, local policy goals, local priorities and leadership influenced decision-making and implementation in the two cities.

Limitations

There was no analysis of active travel outcomes because the available data were not suitable.

Conclusions

The pre-implementation period is important. It helps frame public and political attitudes. The scale of implementation and additional activities in the two cities had a bearing on the impacts. The citywide approach adopted by Edinburgh was effective in reducing speeds and positively affected a range of public health outcomes. The city-centre approach in Belfast (where speeds were already low) was less effective. However, the main outcome of these schemes was a reduction in road casualties at all levels of severity.

Future work

Future work should develop a statistical approach to public health interventions that incorporates variables from multiple outcomes. In this study, each outcome was analysed independently of each other. Furthermore, population measures of active travel that can be administered simply, inexpensively and at scale should be developed.

Study registration

This study is registered as ISRCTN10200526.

Funding

This project was funded by the National Institute for Health and Care Research (NIHR) Public Health Research programme and will be published in full in Public Health Research; Vol. 10, No. 9. See the NIHR Journals Library website for further project information.

The association of socioeconomic deprivation and paediatric open tibia fractures

The primary aim of this study is to test the association of open tibial fractures (OTF), in a paediatric age group, with socioeconomic deprivation. The secondary objectives are to more clearly define the epidemiological characteristics of these high-energy injuries. A consecutive series of patients with OTF presenting to a major trauma centre at a children's hospital in Liverpool had age, gender, fracture pattern, mechanism, timing of the injury and their postcode of residence recorded. Those cases outside Liverpool, Sefton and Knowsley local authorities were excluded from incidence calculations. Postcodes were used to generate deprivation scores (Index of Multiple Deprivation, 2010) based on census data (2011). Cases were ranked and allocated to deprivation quintiles. A comparison to the normal population within Merseyside was undertaken using regression analysis. There were 71 cases over a 9-year period. Fifty cases resided within the geographical limits of Merseyside and were included in the incidence calculations. The annual incidence of paediatric OTF is 3.09 per 100 000 children (0-16 years). The median age at injury was 11 years (range 2-16) and this occurred most usually during term-time between 3 and 5 p.m. from road traffic collisions. Paediatric OTFs are strongly associated with socioeconomic deprivation. The association with deprivation reflects an exposure to unsafe roads in busy urban areas with limited access to safe playing spaces. Socioeconomically deprived men are most at risk from this injury. The links between deprivation and outcomes of treatment or long-term prospects are unclear.

Searching for health equity: validation of a search filter for ethnic and socioeconomic inequalities in transport

BACKGROUND

Efforts to improve health equity should be informed by the best available evidence. However, equity-related research is inconsistently indexed, and uses a variety of terms to describe key concepts, making it difficult to reliably identify all relevant studies. We report the development and validation of a search strategy for studies investigating whether the effects of interventions differ by ethnicity or socio-economic status, using the field of transport and health as an example.

METHODS

Adapting previously described methods, we followed four steps: generation of a test set of eligible studies, search strategy development, search strategy validation, and documentation.

RESULTS

Drawing from 12 systematic reviews, supplemented by additional studies identified by experts and colleagues, we identified a test set of 11 studies that met our eligibility criteria. We assigned five studies to a development set, which we used to develop and refine our search strategy. We assigned the remaining six studies to a validation set, against which we tested our final search strategy. The final search strategy identified all studies in both validation and development sets.

CONCLUSIONS

The validated search strategy derived in this study facilitates the conduct of systematic reviews and other literature searches investigating whether the effects of interventions differ by ethnicity or socio-economic status and may be further developed in future for other equity-focused searches and reviews.

Are There Changes in Inequalities in Injuries? A Review of Evidence in the WHO European Region

Decreases in injury rates globally and in Europe in the past decades, although encouraging, may mask previously reported social inequalities between and within countries that persist or even increase. European research on this issue has not been systematically reviewed, which is the aim of this article. Between and within-country studies from the WHO European Region that investigate changes in social inequalities in injuries over time or in recent decades were sought in PubMed, Scopus, and Web of Science. Of the 27 studies retained, seven were cross-country and 20 were country-specific. Twelve reported changes in inequalities over time and the remaining 15 shed light on other aspects of inequalities. A substantial downward trend in injuries is reported for all causes and cause-specific ones—alongside persisting inequalities between countries and, in a majority of studies, within countries. Studies investigate diverse questions in different population groups. Depending on the social measure and injury outcome considered, many report inequalities in injuries albeit to a varying degree. Despite the downward trends in risk levels, relative social inequalities in injuries remain a persisting public health issue in the European Region.

Visualization and analysis of mapping knowledge domain of road safety studies

Mapping knowledge domain (MKD) is an important application of visualization technology in Bibliometrics, which has been extensively applied in psychology, medicine, and information science. In this paper we conduct a systematic analysis of the development trend on road safety studies based on the Science Citation Index Expanded (SCIE) and Social Sciences Citation Index (SSCI) articles published between 2000 and 2018 using the MKD software tools VOSviewer and Sci2 Tool. Based on our analysis, we first present the annual numbers of articles, origin countries, main research organizations and groups as well as the source journals on road safety studies. We then report the collaborations among the main research organizations and groups using co-authorship analysis. Furthermore, we adopt the document co-citation analysis, keywords co-occurrence analysis, and burst detection analysis to visually explore the knowledge bases, topic distribution, research fronts and research trends on road safety studies. The proposed approach based on the visualized analysis of MKD can be used to establish a reference information and research basis for the application and development of methods in the domain of road safety studies. In particular, our results show that the knowledge bases (classical documents) of road safety studies in the last two decades have focused on five major areas of "Crash Frequency Data Analysis", "Driver Behavior Questionnaire", "Safety in Numbers for Walkers and Bicyclists", "Road Traffic Injury and Prevention", and "Driving Speed and Road Crashes". Among the research topics, the five dominant clusters are "Causation and Injury Severity Analysis of Road Accidents", "Epidemiologic Study and Prevention of Road Traffic Injury", "Intelligent Transportation System and Active Safety", "Young drivers' driving behavior and psychology", and "Older drivers' psychological and physiological characteristics". Finally, the burst keywords in research trends include Cycling, Intelligent Transportation Systems, and Distraction.

Cognitive-Motivational Determinants of Residents' Civic Engagement and Health (Inequities) in the Context of Noise Action Planning: A Conceptual Model

The Environmental Noise Directive expects residents to be actively involved in localising and selecting noise abatement interventions during the noise action planning process. Its intervention impact is meant to be homogeneous across population groups. Against the background of social heterogeneity and environmental disparities, however, the impact of noise action planning on exposure to traffic-related noise and its health effects is unlikely to follow homogenous distributions. Until now, there has been no study evaluating the impact of noise action measures on the social distribution of traffic-related noise exposure and health outcomes. We develop a conceptual (logic) model on cognitive-motivational determinants of residents’ civic engagement and health (inequities) by integrating arguments from the Model on household’s Vulnerability to the local Environment, the learned helplessness model in environmental psychology, the Cognitive Activation Theory of Stress, and the reserve capacity model. Specifically, we derive four hypothetical patterns of cognitive-motivational determinants yielding different levels of sustained physiological activation and expectancies of civic engagement. These patterns may help us understand why health inequities arise in the context of noise action planning and learn how to transform noise action planning into an instrument conducive to health equity. While building on existing frameworks, our conceptual model will be tested empirically in the next stage of our research process.

Quantifying the causal effects of 20mph zones on road casualties in London via doubly robust estimation

This paper estimates the causal effect of 20mph zones on road casualties in London. Potential confounders in the key relationship of interest are included within outcome regression and propensity score models, and the models are then combined to form a doubly robust estimator. A total of 234 treated zones and 2844 potential control zones are included in the data sample. The propensity score model is used to select a viable control group which has common support in the covariate distributions. We compare the doubly robust estimates with those obtained using three other methods: inverse probability weighting, regression adjustment, and propensity score matching. The results indicate that 20mph zones have had a significant causal impact on road casualty reduction in both absolute and proportional terms.

Cycling infrastructure for reducing cycling injuries in cyclists

BACKGROUND

Cycling is an attractive form of transport. It is beneficial to the individual as a form of physical activity that may fit more readily into an individual's daily routine, such as for cycling to work and to the shops, than other physical activities such as visiting a gym. Cycling is also beneficial to the wider community and the environment as a result of fewer motorised journeys. Cyclists are seen as vulnerable road users who are frequently in close proximity to larger and faster motorised vehicles. Cycling infrastructure aims to make cycling both more convenient and safer for cyclists. This review is needed to guide transport planning.

OBJECTIVES

To:1. evaluate the effects of different types of cycling infrastructure on reducing cycling injuries in cyclists, by type of infrastructure;2. evaluate the effects of cycling infrastructure on reducing the severity of cycling injuries in cyclists;3. evaluate the effects of cycling infrastructure on reducing cycling injuries in cyclists with respect to age, sex and social group.

SEARCH METHODS

We ran the most recent search on 2nd March 2015. We searched the Cochrane Injuries Group Specialised Register, CENTRAL (The Cochrane Library), MEDLINE (OvidSP), Embase Classic + Embase(OvidSP), PubMed and 10 other databases. We searched websites, handsearched conference proceedings, screened reference lists of included studies and previously published reviews and contacted relevant organisations.

SELECTION CRITERIA

We included randomised controlled trials, cluster randomised controlled trials, controlled before-after studies, and interrupted time series studies which evaluated the effect of cycling infrastructure (such as cycle lanes, tracks or paths, speed management, roundabout design) on cyclist injury or collision rates. Studies had to include a comparator, that is, either no infrastructure or a different type of infrastructure. We excluded studies that assessed collisions that occurred as a result of competitive cycling.

DATA COLLECTION AND ANALYSIS

Two review authors examined the titles and abstracts of papers obtained from searches to determine eligibility. Two review authors extracted data from the included trials and assessed the risk of bias. We carried out a meta-analysis using the random-effects model where at least three studies reported the same intervention and outcome. Where there were sufficient studies, as a secondary analysis we accounted for changes in cyclist exposure in the calculation of the rate ratios. We rated the quality of the evidence as 'high', 'moderate', 'low' or 'very low' according to the GRADE approach for the installation of cycle routes and networks.

MAIN RESULTS

We identified 21 studies for inclusion in the review: 20 controlled before-after (CBA) studies and one interrupted time series (ITS) study. These evaluated a range of infrastructure including cycle lanes, advanced stop lines, use of colour, cycle tracks, cycle paths, management of the road network, speed management, cycle routes and networks, roundabout design and packages of measures. No studies reported medically-attended or self-reported injuries. There was no evidence that cycle lanes reduce the rate of cycle collisions (rate ratio 1.21, 95% CI 0.70 to 2.08). Taking into account cycle flow, there was no difference in collisions for cyclists using cycle routes and networks compared with cyclists not using cycle routes and networks (RR 0.40, 95% CI 0.15 to 1.05). There was statistically significant heterogeneity between the studies (I² = 75%, Chi² = 8.00 df = 2, P = 0.02) for the analysis adjusted for cycle flow. We judged the quality of the evidence regarding cycle routes and networks as very low and we are very uncertain about the estimate. These analyses are based on findings from CBA studies.From data presented narratively, the use of 20 mph speed restrictions in urban areas may be effective at reducing cyclist collisions. Redesigning specific parts of cycle routes that may be particularly busy or complex in terms of traffic movement may be beneficial to cyclists in terms of reducing the risk of collision. Generally, the conversion of intersections to roundabouts may increase the number of cycle collisions. In particular, the conversion of intersections to roundabouts with cycle lanes marked as part of the circulating carriageway increased cycle collisions. However, the conversion of intersections with and without signals to roundabouts with cycle paths may reduce the odds of collision. Both continuing a cycle lane across the mouth of a side road with a give way line onto the main road, and cycle tracks, may increase the risk of injury collisions in cyclists. However, these conclusions are uncertain, being based on a narrative review of findings from included studies. There is a lack of evidence that cycle paths or advanced stop lines either reduce or increase injury collisions in cyclists. There is also insufficient evidence to draw any robust conclusions concerning the effect of cycling infrastructure on cycling collisions in terms of severity of injury, sex, age, and level of social deprivation of the casualty.In terms of quality of the evidence, there was little matching of intervention and control sites. In many studies, the comparability of the control area to the intervention site was unclear and few studies provided information on other cycling infrastructures that may be in place in the control and intervention areas. The majority of studies analysed data routinely collected by organisations external to the study team, thus reducing the risk of bias in terms of systematic differences in assessing outcomes between the control and intervention groups. Some authors did not take regression-to-mean effects into account when examining changes in collisions. Longer data collection periods pre- and post-installation would allow for regression-to-mean effects and also seasonal and time trends in traffic volume to be observed. Few studies adjusted cycle collision rates for exposure.

AUTHORS' CONCLUSIONS

Generally, there is a lack of high quality evidence to be able to draw firm conclusions as to the effect of cycling infrastructure on cycling collisions. There is a lack of rigorous evaluation of cycling infrastructure.

On the buses: a mixed-method evaluation of the impact of free bus travel for young people on the public health

Background

In September 2005 London introduced a policy granting young people aged < 17 years access to free bus and tram travel. A year later this policy was extended to people aged < 18 years in education, work or training. This intervention was part of a broader environmental strategy in London to reduce private car use, but its primary aim was to decrease ‘transport exclusion’, and ensure that access to goods, services, education and training opportunities were not denied to some young people because of transport poverty. However, there were also likely to be positive and negative health implications, which were difficult to assess in the absence of a robust evidence base on the impact of transport policies on health and well-being.

Objectives

To evaluate the impact of free bus travel for young people in London on the public health. Specifically, to provide empirical evidence for the impact of this ‘natural experiment’ on health outcomes and behaviours (e.g. injuries, active travel) for young people; explore the effects on the determinants of health; identify the effects on older citizens of increased access to bus travel for young people and to identify whether or not the intervention represented value for money.

Design

Quasi-experimental design, using secondary analysis of routine data, primary qualitative data and literature reviews.

Setting

London, UK.

Participants

Young people aged 12–17 years and older citizens aged ≥ 60 years.

Intervention

The introduction of free bus travel for those aged < 17 years living in London in 2005, extended to those aged < 18 years in 2006.

Main outcome measures

Quantitative: number of journeys to school or work; frequency and distance of active travel (i.e. walking and/or cycling), bus travel, car travel; incidence of road traffic injuries and assaults and socioeconomic gradients in travel patterns. Qualitative: how free bus travel affected young people and older citizens’ travel and well-being.

Methods

Quantitative component: change-on-change analysis comparing pre–post change in the target age group (12–17 years) against that seen in ‘non-exposed’ groups [for travel mode, road traffic injury (RTI) and assaults]. Qualitative component: interviews analysed using both deductive and inductive methods. Economic evaluation: cost–benefit analysis (CBA).

Data sources

London Area Transport Survey (LATS) and London Travel Demand Survey (LTDS) (travel mode); STATS19 Road Accident data set (RTI); Hospital Episode Statistics (HES) (assaults); interviews with young people and older citizens; and cost data from providers and literature reviews.

Results

The introduction of free bus travel for young people was associated with higher use of bus travel by adults and young people [31% increase, 95% confidence interval (CI) 19% to 42%; and 26% increase, 95% CI 13% to 41%, respectively], especially for short journeys, and lower car distances relative to adults (relative change 0.73, 95% CI 0.55 to 0.94); no significant overall reduction in ‘active travel’ [reduction in number of walking trips but no evidence of change in distance walked (relative change 0.99, 95% CI 0.92 to 1.07)]; significant reduction in cycling relative to adults (but from a very low base); a reduction in road traffic injuries for car occupants (relative change 0.89, 95% CI 0.84 to 0.95) and cyclists (relative change 0.60, 95% CI 0.55 to 0.66), but not pedestrians; an overall modest increase in journeys to work or school (relative change 1.09, 95% CI 1.06 to 1.14); equivocal evidence of impact on socioeconomic gradients in travel behaviour and no evidence of adverse impact on travel of older people aged > 60 years. An increase in assaults largely preceded the scheme. Qualitative data suggested that the scheme increased opportunities for independent travel, social inclusion, and a sense of belonging and that it ‘normalised’ bus travel. The monetised benefits of the scheme substantially outweighed the costs, providing what the Department for Transport (DfT) considers ‘high’ value for money.

Conclusion

The free bus travel scheme for young people appears to have encouraged their greater use of bus transport for short trips without significant impact on their overall active travel. There was qualitative evidence for benefits on social determinants of health, such as normalisation of bus travel, greater social inclusion and opportunities for independent travel. In the context of a good bus service, universal free bus travel for young people appears to be a cost-effective contributor to social inclusion and, potentially, to increasing sustainable transport in the long term. Further research is needed on the effects of both active and other travel modes on the determinants of health; the factors that influence maintenance of travel mode change; travel as ‘social practice’; the impact of driving license changes on injury rates for young adults and the value of a statistical life for young people.

Funding

The National Institute for Health Research Public Health Research programme.

Ethnic, socioeconomic and geographical inequalities in road traffic injury rates in the Auckland region

OBJECTIVE

To describe ethnic, socioeconomic and geographical differences in road traffic injury (RTI) within Auckland, New Zealand's largest city.

METHODS

We analysed rates of RTI deaths and non-fatal hospital admissions using the New Zealand Mortality Collection and the National Minimum Data Set 2000-08. Poisson regression examined the association of age, gender, prioritised ethnicity and small area deprivation (New Zealand Index of Deprivation) with RTI rates, and RTI rates were mapped for 21 local board areas within the Auckland region.

RESULTS

While RTI rates increased with levels of deprivation in all age groups, the gradient was steepest among children (9% increase/decile) and adults aged 25-64 years (11% increase/decile). In all age groups, RTI risk was highest among Māori. Pacific children had an elevated risk of RTI compared with the NZ European/Other group, but Pacific youth (15-24 years) and adults (25-64 years) had a lower risk. While RTI rates were generally higher for those living in rural local board areas, all but one local board in the southern Auckland urban area had among the highest rates.

CONCLUSIONS

There are substantial ethnic, socioeconomic and geographic inequalities in RTI risk in the Auckland region, with high rates among Māori (all ages), Pacific children, people living in socioeconomically deprived neighbourhoods, the urban south and rural regions.

IMPLICATIONS

To meet the vision of regional plans, road safety efforts must prioritise vulnerable communities at greatest risk of RTI, and implement and monitor the effectiveness of strategies that specifically include a focus on reducing inequalities in RTI rates.