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ToolsHunter, Ruth F., Cleland, Claire L., Busby, John, Nightingale, Glenna, Kee, Frank, Williams, Andrew James, Kelly, Paul, Kelly, Michael P., Milton, Karen, Kokka, Kelly and Jepson, Ruth (2023) Investigating the impact of a 20mph speed limit intervention on road traffic collisions, casualties, speed and volume in Belfast, UK: 3-year follow-up outcomes of a natural experiment. Journal of Epidemiology and Community Health, 77 (1). pp. 17-25. ISSN 0143-005X
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Abstract
Background: Evidence regarding the effectiveness of 20 miles per hour (mph) speed limit interventions is limited, and rarely have long-term outcomes been assessed. We investigate the effect of a 20 mph speed limit intervention on road traffic collisions, casualties, speed and volume at 1 and 3 years post-implementation. Methods: An observational, repeated cross-sectional design was implemented, using routinely collected data for road traffic collisions, casualties, speed and volume. We evaluated difference-in-differences in collisions and casualties (intervention vs control) across three different time series and traffic speed and volume pre-implementation, at 1 and 3 years post-implementation. Results: Small reductions in road traffic collisions were observed at year 1 (3%; p=0.82) and year 3 post-implementation (15%; p=0.31) at the intervention site. Difference-in-differences analyses showed no statistically significant differences between the intervention and control sites over time for road traffic collisions. There were 16% (p=0.18) and 22% (p=0.06) reductions in casualty rates at years 1 and 3 post-implementation, respectively, at the intervention site. Results showed little change in mean traffic speed at year 1 (0.2 mph, 95% CI −0.3 to 2.4, p=0.14) and year 3 post-implementation (0.8, 95% CI −1.5 to 2.5, p=0.17). For traffic volume, a decrease in 57 vehicles per week was observed at year 1 (95% CI –162 to −14, p<0.00) and 71 vehicles at year 3 (95% CI −213 to 1, p=0.05) post-implementation. Conclusion: A 20 mph speed limit intervention implemented at city centre scale had little impact on long-term outcomes including road traffic collisions, casualties and speed, except for a reduction in traffic volume. Policymakers considering implementing 20 mph speed limit interventions should consider the fidelity, context and scale of implementation.
| Item Type: | Article |
|---|---|
| Uncontrolled Keywords: | epidemiology,prevention,public health,epidemiology,public health, environmental and occupational health ,/dk/atira/pure/subjectarea/asjc/2700/2713 |
| Faculty \ School: | Faculty of Medicine and Health Sciences > Norwich Medical School |
| UEA Research Groups: | Faculty of Medicine and Health Sciences > Research Centres > Lifespan Health Faculty of Medicine and Health Sciences > Research Centres > Population Health |
| Related URLs: | |
| Depositing User: | LivePure Connector |
| Date Deposited: | 30 Jan 2023 10:30 |
| Last Modified: | 28 Mar 2025 12:01 |
| URI: | https://ueaeprints.uea.ac.uk/id/eprint/90856 |
| DOI: | 10.1136/jech-2022-219729 |
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