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.

A matched case-control approach to identify the risk factors of fatal pedestrian crashes on a six-lane rural highway in India

Globally, the increase in pedestrian fatalities due to road traffic crashes (RTCs) on transport networks has been a major concern. In low- and middle-income countries (LMICs), pedestrians face a high risk due to RTCs on the rural highway network. The safety evaluation methods, such as observational before-after, empirical Bayes, full Bayes, and cross-sectional methods have been used to identify risk factors of RTCs. However, these methods are data-intensive and have associated limitations. Thus, this study employed a matched case-control method to identify the risk factors of fatal pedestrian crashes. This study utilized crash, traffic volume, speed, geometric, and roadside environment data of a 175 km six-lane rural highway in India. The identified major risk factors, such as clear zone width, the presence of habitation, service roads, and horizontal curve sections, increase the likelihood of a fatal pedestrian crash. This study provides specific insights for modifying the speed limit of highway sections passing through habitation. On such highway sections, designers should shift focus to pedestrian safety. It also suggests that the service road design needs to be reconsidered from a pedestrian safety viewpoint. The proposed method can be used in any other setting having similar traffic and socio-economic conditions.

Developing a national database of police-reported fatal road traffic crashes for road safety research and management in India

Strengthening crash surveillance is an urgent priority for road safety in low- and middle-income countries. We reviewed the online availability and completeness of First Information Reports (FIRs; police reports) of road traffic crashes in India. We developed a relational database to record information extracted from FIRs, and implemented it for one state (Chhattisgarh, 2017-2019). We found that FIRs can be downloaded in bulk from government websites of 15 states and union territories. Another 14 provide access online but restrict bulk downloading, and 7 do not provide online access. For Chhattisgarh, 87% of registered FIRs could be downloaded. Most FIRs reported the date, time, collision-type, and vehicle-types, but important crash characteristics (e.g. infrastructure attributes) were missing. India needs to invest in building the crash surveillance capacity for research and safety management. However, in the interim, maintaining a national database of a sample of FIRs can provide useful policy guidance.

Built-environment risk assessment for pedestrians near bus-stops: a case study in Delhi

Pedestrian safety is a serious concern in the developing nations of the world. It is evident from the past studies that built-environment characteristics near bus-stops, play a crucial role on the frequency and overall share of pedestrian deaths and injuries in road traffic crashes. The present study aims to identify critical built-environment features around vulnerable bus-stops in an Indian city and evaluate the odds of risk that prevails on the safety of pedestrians near bus stops. Hotspot analysis was conducted to finalise 177 bus stop sites within high-crash clusters in the study area. Built-environment attributes considered were based on sidewalk, crosswalk and bus stop conditions near such vulnerable locations. This study includes a video graphic and manual field survey conducted during the day and night-time. Logistic regression was applied to estimate the impact of built environment features on pedestrian crashes. Width and disability friendliness of sidewalks, presence of bus bays and on-street parking have significant impacts on pedestrian fatalities at locations with a higher share of pedestrian fatalities during the day. On the other hand, presence of zebra crossings at junctions, proper bus stop lighting and high sidewalks reduce the odds of pedestrian crashes at night near bus stops.

Factors explaining pedestrian-involved fatality crashes on National Highways in India

Pedestrians continue to face high risk of getting involved in fatal and serious injury crashes all over the world. In many high-income countries, pedestrian involvement in fatal crashes occur mostly in urban areas. However, in many low- and middle-income countries in Asia and Africa, pedestrian involvement in fatal crashes occur on intercity highways too. This research analyses fatal pedestrian crash characteristics, and identifies probable contributory factors to pedestrian involvement in fatal crashes using logistic regression for two-, four-, and six-lane National Highways. The fatal pedestrian crash density is found to be the highest at 1.37 crashes/km/year on six-lane divided NH-1. The binary logistic regression estimation results for pedestrian involvement in the fatal crash model revealed that the predictors: "number of lanes" and "time of crash" are found to be significant at 95% level. The model results for the variable "number of lanes" highlights the need to study pedestrian crossing behaviour on highways in detail. The design standards for pedestrian crossing facilities in urban areas may not be suitable for National Highways in particular multi-lane highways. In-depth research is required to understand the suitability of various traffic calming measures and other possible interventions which can ensure pedestrian safety on highways.

A systematic review and meta-analysis of the impact of curbs on crash outcomes

INTRODUCTION

Road traffic crashes involving vertical curbs are commonly reported to occur on highways and expressways in India. We found a gap in terms of systematically assessing the evidence of the impact of curbs on road safety outcomes in the real world.

METHOD

We conducted a systematic review and meta-analysis of the impact of curbs on the risk of road traffic injuries. We used keywords in a database of records prepared by an earlier evidence gap map (EGM). The EGM used a comprehensive search strategy including 6 academic database, 17 organizational websites, hand searching, contacting experts and back referencing.

RESULTS

We found 4 studies that evaluated impact of a curbed median or a curbed shoulder. We found that the presence of a curb on a median increases the risk for all crashes, all single-vehicle crashes, all median-related crashes and median-related injury crashes. The data also indicate that the severity of accidents reduces for curbs on median while it increases for curbs on shoulder, though the latter effect is not statistically significant. All the epidemiological studies were conducted on rural highways and did not report effects for different traffic speeds or vehicle types. However, our review of crash tests and simulation studies indicates that the impact of a curb design may be highly sensitive to speed and vehicle types.

CONCLUSIONS

The safety impacts of a curb depend on the context of the road. In an urban road, a curb should ensure safety of pedestrians from an errant vehicle. On high-speed rural roads, curbs should be avoided and treatments should facilitate safe departure of the vehicle from the roadway.

Identification and analysis of offenders causing hit and run accidents using classification algorithms

Hit-and-run crashes are significant concern for many countries. Due to lack of information of offending vehicles it is difficult to understand dynamics of these crashes to have a prevention plan. The paper aims to identify the impacting vehicle in hit-and-run crashes. We studied fatal road crashes of New Delhi for eleven years (2006-2016) and found that approximately 40% fatal crashes are hit-and-run with unknown impacting vehicles. We proposed a framework using eleven different machine learning-based classification algorithms - Logistic-Regression, KNN, SVM-Linear and RBF-Kernel, Naïve-Bayes, Random-Forest, DecisionTree, AdaBoost, Multilayer-Perceptron, CART and Linear-Discriminant-Analysis. We found SVM-linear-kernel gave best results. Results reveal that cars, buses, and heavy vehicles are involved vehicles in hit-and-run crashes. Buses were primary cause leading to 39% of hit-and-run during 2006-2009 thereafter cars increased drastically. Our framework is robust and scalable to any city. The outcomes provide inputs to traffic engineers for better policy prescription and road user safety.

A performance analysis of prediction techniques for impacting vehicles in hit-and-run road accidents

Road accidents are globally accepted challenges. They are one of the significant causes of deaths and injuries besides other direct and indirect losses. Countries and international organizations have designed technologies, systems, and policies to prevent accidents. However, hit-and-run accidents remain one of the most dangerous types of road accidents as the information about the vehicle responsible for the accident remain unknown. Therefore, any mechanism which can provide information about the impacting vehicle in hit-and-run accidents will be useful in planning and executing preventive measures to address this road menace. Since there exist several models to predict the impacting unknown vehicle, it becomes important to find which is the most accurate amongst those available. This research applies a process-based approach that identifies the most accurate model out of six supervised learning classification models viz. Logistic Reasoning, Linear Discriminant Analysis, Naïve Bayes, Classification and Regression Trees, k-Nearest Neighbor and Support Vector Machine. These models are implemented using five-fold and ten-fold cross validation, on road accident data collected from five mid-sized Indian cities: Agra, Amritsar, Bhopal, Ludhiana, and Vizag (Vishakhapatnam).This study investigates the possible input factors that may have effect on the performance of applied models. Based on the results of the experiment conducted in this study, Support Vector Machine has been found to have the maximum potentiality to predict unknown impacting vehicle type in hit-and-run accidents for all the cities except Amritsar. The result indicates that, Classification and Regression Trees have maximum accuracy, for Amritsar. Naïve Bayes performed very poorly for the five cities. These recommendations will help in predicting unknown impacting vehicles in hit-and-run accidents. The outcome is useful for transportation authorities and policymakers to implement effective road safety measures for the safety of road users.

Defining pathways to healthy sustainable urban development

Goals and pathways to achieve sustainable urban development have multiple interlinkages with human health and wellbeing. However, these interlinkages have not been examined in depth in recent discussions on urban sustainability and global urban science. This paper fills that gap by elaborating in detail the multiple links between urban sustainability and human health and by mapping research gaps at the interface of health and urban sustainability sciences. As researchers from a broad range of disciplines, we aimed to: 1) define the process of urbanization, highlighting distinctions from related concepts to support improved conceptual rigour in health research; 2) review the evidence linking health with urbanization, urbanicity, and cities and identify cross-cutting issues; and 3) highlight new research approaches needed to study complex urban systems and their links with health. This novel, comprehensive knowledge synthesis addresses issue of interest across multiple disciplines. Our review of concepts of urban development should be of particular value to researchers and practitioners in the health sciences, while our review of the links between urban environments and health should be of particular interest to those outside of public health. We identify specific actions to promote health through sustainable urban development that leaves no one behind, including: integrated planning; evidence-informed policy-making; and monitoring the implementation of policies. We also highlight the critical role of effective governance and equity-driven planning in progress towards sustainable, healthy, and just urban development.

Laser-driven x-ray and proton micro-source and application to simultaneous single-shot bi-modal radiographic imaging

Radiographic imaging with x-rays and protons is an omnipresent tool in basic research and applications in industry, material science and medical diagnostics. The information contained in both modalities can often be valuable in principle, but difficult to access simultaneously. Laser-driven solid-density plasma-sources deliver both kinds of radiation, but mostly single modalities have been explored for applications. Their potential for bi-modal radiographic imaging has never been fully realized, due to problems in generating appropriate sources and separating image modalities. Here, we report on the generation of proton and x-ray micro-sources in laser-plasma interactions of the focused Texas Petawatt laser with solid-density, micrometer-sized tungsten needles. We apply them for bi-modal radiographic imaging of biological and technological objects in a single laser shot. Thereby, advantages of laser-driven sources could be enriched beyond their small footprint by embracing their additional unique properties, including the spectral bandwidth, small source size and multi-mode emission.

Here the authors show a synchronized single-shot bi-modal x-ray and proton source based on laser-generated plasma. This source can be useful for radiographic and tomographic imaging.

Strengthening the Capacity of Emergency Medical Services in Low and Middle Income Countries using Dispatcher-Coordinated Taxis

International standards recommend provision of 1 ambulance for every 50,000 people to fulfil demand for transporting patients to definitive care facilities in Low and Middle Income Countries (LMICs). Governments' consistent attempt to build capacity of emergency medical services (EMS) in LMICs has been financially demanding. This study is an attempt to assess the feasibility of capacity building of existing EMS in Delhi, India by using taxis as an alternative mode of transport for emergency transportation of road traffic crash victims to enable improvement in response time for road traffic crashes where time criticality is deemed important. Performance of the proposed system is evaluated based on response time, coverage and distance. The system models the performance and quantifies the taxi - ambulance configuration for achieving EMS performance within international standards.

PROTOCOL: Effectiveness of road safety interventions: An evidence and gap map

The Decade of Action for Road Safety 2011-2020, officially proclaimed by the UN General Assembly in March 2010, sought to reduce morbidity and mortality due to road traffic injuries (RTI) significantly. While there is reasonable agreement internationally on safer designs of motor vehicles (except locally produced vehicles like three-wheeled scooter taxis, tuk-tuks, jeepneys, etc.), there is a lack of evidence based interventions in road and infrastructure design, police enforcement and post-crash care. Researchers in the field of traffic safety have been aware of the existence of counterintuitive results in their area of work for more than four decades. The fact that many interventions do not result in reductions in RTI is mainly because a large number of studies only measure intermediate outcomes like change in behaviour or knowledge and not the actual results in the field. The scope of this evidence and gap map (EGM) is to cover relevant studies in road safety sector from all countries and present the effectiveness of interventions in terms of mainly traffic crash injuries as its outcome. The interventions adopted in this EGM are classified into five broad categories: Human factors, vehicle factors and protective devices, road design, infrastructure and traffic control, post-crash pre-hospital care and legal and institutional framework. In order to come closer to accomplishing targets for road safety, it is important to allocate resources to promote interventions that are effective in achieving outcomes in the context of road safety. A mapping will provide a comprehensive overview of existing knowledge in the area of road safety and its effectiveness across the world. The map will guide programme managers to high quality evidence and inform targeted commissioning of future research.

Progress in pedestrian safety research

This paper looks at the pedestrian safety issue and the research that has followed to understand and solve the problem of pedestrian safety in the last 120 years - since the time of the first reported pedestrian fatality in 1899. Researches have studied the epidemiology of pedestrian crashes, pedestrian behaviour, pedestrian movements and pedestrian flows. The suggested strategies to reduce pedestrian crashes have ranged from controlling vehicular speeds to controlling pedestrian behaviour. This study presents a summary of the progress we have made in understanding pedestrian crash patterns. Pedestrian behaviour observed in different regions of the world tend to have similarity in pedestrian behaviour: gap acceptance, preferences of route choice and location for crossing roads. High income countries(HIC) have reported reduction in pedestrian fatalities as compared to low and middle income countries(LMICs), however pedestrian trips have also reduced in these countries leading to concerns about the effectiveness of 'known' strategies. Speed control through active measures have been found to have themaximal benefit and education and training programs for altering pedestrian behaviour on the road the least benefits. Low and middle income countries face pedestrian exposure on high speed roads. New research efforts are required to address pedestrian safety in both HIC and LMICs.

The care and transport of trauma victims by layperson emergency medical systems: a qualitative study in Delhi, India

Introduction

Ambulance-based emergency medical systems (EMS) are expensive and remain rare in low- and middle-income countries, where trauma victims are usually transported to hospital by passing vehicles. Recent developments in transportation network technologies could potentially disrupt this status quo by allowing coordinated emergency response from layperson networks. We sought to understand the barriers to bystander assistance for trauma victims in Delhi, India, and implications for a layperson-EMS.

Methods

We used qualitative methods to analyse data from 50 interviews with frontline stakeholders (including taxi drivers, medical professionals, legal experts and police), one stakeholder consultation and a review of documents.

Results

Respondents noted that most trauma victims in Delhi are rapidly brought to hospital by bystanders, taxis and police. While ambulances are common, they are primarily used for interfacility transfers. Entrenched medico-legal practices result in substantial police presence at the hospital, which is a major source of harassment of good Samaritans and interferes with patient care. Trauma victims are often turned away by for-profit hospitals due to their inability to pay, leading to delays in treatment. Recent policy efforts to circumscribe the role of police and force for-profit hospitals to stabilise patients appear to have been unsuccessful.

Conclusions

Existing healthcare and medico-legal practices in India create large systemic impediments to improving trauma outcomes. Until India’s ongoing health and transport sector reforms succeed in ensuring that for-profit hospitals reliably provide care, good Samaritans and layperson-EMS providers should take victims with uncertain financial means to public facilities. To avoid difficulties with police, providers of a layperson-EMS would likely need official police sanction and carry visible symbols of their authority to provide emergency transport. Delhi already has several key components of an EMS (including dispatcher coordinated police response, large ambulance fleet) that could be integrated and expanded into a complete system of emergency care.

Gradient magnet design for simultaneous detection of electrons and positrons in the intermediate MeV range

We report the design and development of a compact electron and positron spectrometer based on tapered neodymium iron boron magnets to characterize the pairs generated in laser-matter experiments. The tapered design forms a gradient magnetic field component allowing energy dependent focusing of the dispersed charged particles along a chosen detector plane. The mirror symmetric design allows for simultaneous detection of pairs with energies from 2 MeV to 500 MeV with an accuracy of ≤10% in the wide energy range from 5 to 110 MeV for a parallel beam incident on a circular aperture of 20 mm. The energy resolution drops to ≤20% for 4-90 MeV range for a divergent beam originating from a point source at 20 cm away (i.e., a solid angle of ∼8 milli steradians), with ≤10% accuracy still maintained in the narrower energy range from 10 to 55 MeV. It offers higher solid angle acceptance, even for the divergent beam, compared to the conventional pinhole aperture-based spectrometers. The proposed gradient magnet is suitable for the detection of low flux and/or monoenergetic type electron/positron beams with finite transverse sizes and offers unparalleled advantages for gamma-ray spectroscopy in the intermediate MeV range.

Going to the nearest hospital vs. designated trauma centre for road traffic crashes: estimating the time difference in Delhi, India

Background: Time to hospital after a road traffic crash (RTC) plays a vital role in determining the outcome for crash victims. In Delhi, there are seven designated trauma centres where crash victims are typically taken, which may not be nearest hospital. We compare the transport time access (crash to hospital) depending on whether the victim is transported to a designated trauma centre or the nearest hospital. Data and methods: For each RTC geocoded manually from police records, the nearest hospital and the designated trauma centre is identified using Google Maps places nearby Search API and guidelines. Travel time matrix is generated between RTC's and identified hospitals using Google maps distance matrix API. Index accounting inter-district differences is developed. Results and conclusions: The network of designated trauma centres in New Delhi is located such that they can be accessed within 45 min of most crashes while nearest hospital within 30 min. As a result, the vast majority of crash victims are likely to receive timely care if they are rapidly transferred to either of these caregivers. However, for the most severely injured and time-sensitive cases, bypassing nearest hospital for trauma care, could substantially improve survival outcomes.

Factors contributing to motorcycle fatal crashes on National Highways in India

This study analyses fatal crash patterns, and identifies the risk factors contributing to motorcycle versus non-motorcycle fatal crashes using binomial logistic regression on two-, four- and six-lane National Highways (NHs) in India utilizing police fatal crash data. The distribution of victims' mode by striking vehicles shows that percentage share of striking vehicles (truck) against the victims' vehicles (motorcycle) is 44%, 52% and 37% on two-lane NH-8, four-lane NH-24 and six-lane NH-1, respectively. Nine explanatory variables pertaining to fatal crash, victim, roadway and environment are considered for the model (using combined data of cited three NHs). The results of the logistic regression model (motorcycle versus non-motorcycle fatal crashes) show that for variable 'collision type', likelihood of occurrence of 'rear-end', 'sideswipe' and 'head-on' fatal crashes are 42-times, 35-times and 25-times more than 'hit pedestrian' respectively. Similarly, for variable 'number of vehicle', likelihood is thrice as 'single-vehicle' than 'two or more vehicles'; and, for variable 'number of lane', probability is more on 'two-lane' NH-8 than 'four-lane' NH-24. Based on the study results, it is recommended to upgrade two-lane (undivided carriageway) to four-lane (divided carriageway) NHs to reduce 'head-on' collision.

Correlates of fatality risk of vulnerable road users in Delhi

Pedestrians, cyclists, and users of motorised two-wheelers account for more than 85% of all the road fatality victims in Delhi. The three categories are often referred to as vulnerable road users (VRUs). Using Bayesian hierarchical approach with a Poisson-lognormal regression model, we present spatial analysis of road fatalities of VRUs with wards as areal units. The model accounts for spatially uncorrelated as well as correlated error. The explanatory variables include demographic factors, traffic characteristics, as well as built environment features. We found that fatality risk has a negative association with socio-economic status (literacy rate), population density, and number of roundabouts, and has a positive association with percentage of population as workers, number of bus stops, number of flyovers (grade separators), and vehicle kilometers travelled. The negative effect of roundabouts, though statistically insignificant, is in accordance with their speed calming effects for which they have been used to replace signalised junctions in various parts of the world. Fatality risk is 80% higher at the density of 50 persons per hectare (pph) than at overall city-wide density of 250 pph. The presence of a flyover increases the relative risk by 15% compared to no flyover. Future studies should investigate the causal mechanism through which denser neighborhoods become safer. Given the risk posed by flyovers, their use as congestion mitigation measure should be discontinued within urban areas.

Land use, transport, and population health: estimating the health benefits of compact cities

Using a health impact assessment framework, we estimated the population health effects arising from alternative land-use and transport policy initiatives in six cities. Land-use changes were modelled to reflect a compact city in which land-use density and diversity were increased and distances to public transport were reduced to produce low motorised mobility, namely a modal shift from private motor vehicles to walking, cycling, and public transport. The modelled compact city scenario resulted in health gains for all cities (for diabetes, cardiovascular disease, and respiratory disease) with overall health gains of 420-826 disability-adjusted life-years (DALYs) per 100 000 population. However, for moderate to highly motorised cities, such as Melbourne, London, and Boston, the compact city scenario predicted a small increase in road trauma for cyclists and pedestrians (health loss of between 34 and 41 DALYs per 100 000 population). The findings suggest that government policies need to actively pursue land-use elements-particularly a focus towards compact cities-that support a modal shift away from private motor vehicles towards walking, cycling, and low-emission public transport. At the same time, these policies need to ensure the provision of safe walking and cycling infrastructure. The findings highlight the opportunities for policy makers to positively influence the overall health of city populations.