F Bunn

Traffic calming for the prevention of road traffic injuries: systematic review and meta-analysis

Objective: To assess whether area-wide traffic calming schemes can reduce road crash related deaths and injuries. Design: Systematic review and meta-analysis. Data sources: Cochrane Injuries Group Specialised Register, Cochrane Central Register of Controlled Trials, Medline, EMBASE, Sociological Abstracts Science (and social science) citation index, National Technical Information service, Psychlit, Transport Research Information Service, International Road Research Documentation, and Transdoc, and web sites of road safety organisation were searched; experts were contacted, conference proceedings were handsearched, and relevant reference lists were checked. Inclusion criteria: Randomised controlled trials, and controlled before/after studies of area-wide traffic calming schemes designed to discourage and slow down through traffic on residential roads. Methods: Data were collected on road user deaths, injuries, and traffic crashes. For each study rate ratios were calculated, the ratio of event rates before and after intervention in the traffic calmed area divided by the corresponding ratio of event rates in the control area, which were pooled to give an overall estimate using a random effects model. Findings: Sixteen controlled before/after studies met our inclusion criteria. Eight studies reported the number of road user deaths: pooled rate ratio 0.63 (95% confidence interval (CI) 0.14 to 2.59). Sixteen studies reported the number of injuries (fatal and non-fatal): pooled rate ratio 0.89 (95% CI 0.80 to 1.00). All studies were in high income countries. Conclusion: Area-wide traffic calming in towns and cities has the potential to reduce road traffic injuries. However, further rigorous evaluations of this intervention are needed, especially in low and middle income countries.

Identifying controlled evaluation studies of road safety interventions: Searching for needles in a haystack

Problem: Worldwide, over one million people die and about 10 million people sustain permanent disabilities each year in road traffic crashes. It is a matter of urgency that effective strategies, especially from existing controlled trials (CTs), are identified for crash prevention programs. Methods: We used word frequency analysis to develop a search strategy of known sensitivity and positive predictive value (PPV) to identify reports of controlled evaluation studies of road safety interventions in the TRANSPORT database. Results: 23,554 records were searched and 319 (1.4%) records of controlled evaluation studies were identified by handsearching. We were unable to devise search strategies that combined acceptable sensitivity and PPV. Impact on industry: Efforts to improve the identification of CTs of road safety interventions are urgently required. This would involve the documentation of the study design in the title, abstract, and methods section of the research report. The study methodology should be carefully and consistently indexed in road safety databases, and editors can encourage appropriate indexing by insisting on the use of structured abstracts that give details of study methodology.