Area-wide traffic calming for preventing traffic related injuries: Cochrane systematic review

Abstract

Assessed as up to date: 2007/12/31

Background

It is estimated that by 2020 road traffic crashes will have moved from ninth to third in the world disease burden ranking, as measured in disability adjusted life years, and to second in developing countries. Area-wide traffic calming schemes that discourage through traffic on residential roads is one strategy for preventing traffic related injuries.

Objectives

To assess the effects of area-wide traffic calming for preventing traffic related crashes, injuries, and deaths.

Search strategy

We searched the the Cochrane Injuries Group Specialised Register, Cochrane Central Register of Controlled Trials, MEDLINE, EMBASE and TRANSPORT. We searched the web sites of road safety organisations, handsearched conference proceedings, checked reference lists of relevant papers and contacted experts in the area. The search was not restricted by language or publication status. The searches were last updated in 2008.

Selection criteria

Randomised controlled trials and controlled before-after studies of area-wide traffic calming schemes.

Data collection and analysis

Two authors independently extracted data on type of study, characteristics of intervention and control areas, and length of data collection periods. Before and after data were collected on the total number of road traffic crashes, all road user deaths and injuries, pedestrian-motor vehicle collisions and road user deaths. The results of each study were expressed as rate ratios.

Main results

We found no randomised controlled trials, but 22 controlled before-and-after studies met our inclusion criteria. Seven studies were conducted in Germany, seven in the UK, two in Australia, two in the Netherlands, two in Denmark, one in Japan, and one in Spain. There were no studies in low or middle income countries. Nine trials reported the number of road traffic crashes resulting in deaths; pooled rate ratio 0.79 (95% CI 0.23 to 2.68). Eighteen studies reported the number of road traffic crashes resulting in injuries (fatal and non-fatal); pooled rate ratio 0.85 (95% CI 0.75 to 0.96). Twelve studies reported the total number of road traffic crashes; pooled rate ratio 0.89 (95% CI 0.76 to 1.05). Fourteen trials reported the number of pedestrian-motor vehicle collisions; pooled rate ratio 1.01 (95% CI 0.88 to 1.16). There was evidence of significant heterogeneity for the total number of crashes and road user injuries outcomes.

Authors' conclusions

The results from this review suggest that area-wide traffic calming in towns and cities may be a promising intervention for reducing the number of road traffic injuries and deaths. However, further rigorous evaluations of such interventions are needed.

Author(s)

Bunn Frances, Collier Timothy, Frost Chris, Ker Katharine, Steinbach Rebecca, Roberts Ian, Wentz Reinhard

Summary

Area-wide traffic calming (such as introducing road/speed humps) may reduce death and injury from road traffic crashes but more research is needed

Road traffic crashes are a major problem worldwide. In high-income countries, traffic calming schemes aim to make the roads safer (particularly for vulnerable road users such as pedestrians and cyclists) in areas that are particular 'hot spots'. Strategies include slowing down traffic (eg road/speed humps, mini-roundabouts, reduced speed limit zones), visual changes (road surface treatment, changes to road lighting), redistributing traffic (blocking roads, creating one-way streets), and/or changes to road environments (such as trees). This review found that area-wide traffic calming may have the potential to reduce death and injuries, but more research is needed particularly in low and middle income countries.

Reviewer's Conclusions

Implications for practice

Area-wide traffic calming appears to be a promising intervention for reducing traffic injuries and deaths in towns and cities. However, further rigorous evaluation is needed before we can answer the question conclusively.

Implications for research

In searching for studies of traffic calming we found numerous uncontrolled before-after studies but only 22 controlled before-after studies and no randomised controlled trials. Traffic calming interventions need to be properly evaluated using well-designed controlled studies, so that we can more accurately estimate their effects. In addition, researchers need to assess the effect of these interventions in middle and lower income countries.

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