Grundy Chris, Steinbach Rebecca, Edwards Phil, Green Judith, Armstrong Ben, Wilkinson Paul
Department of Public Health and Policy, London School of Hygiene and Tropical Medicine, London WC1E 7HT.
BMJ. 2009 Dec 10;339:b4469. doi: 10.1136/bmj.b4469.
To quantify the effect of the introduction of 20 mph (32 km an hour) traffic speed zones on road collisions, injuries, and fatalities in London.
Observational study based on analysis of geographically coded police data on road casualties, 1986-2006. Analyses were made of longitudinal changes in counts of road injuries within each of 119 029 road segments with at least one casualty with conditional fixed effects Poisson models. Estimates of the effect of introducing 20 mph zones on casualties within those zones and in adjacent areas were adjusted for the underlying downward trend in traffic casualties.
London.
All casualties from road collisions; those killed and seriously injured (KSI).
The introduction of 20 mph zones was associated with a 41.9% (95% confidence interval 36.0% to 47.8%) reduction in road casualties, after adjustment for underlying time trends. The percentage reduction was greatest in younger children and greater for the category of killed or seriously injured casualties than for minor injuries. There was no evidence of casualty migration to areas adjacent to 20 mph zones, where casualties also fell slightly by an average of 8.0% (4.4% to 11.5%). Conclusions 20 mph zones are effective measures for reducing road injuries and deaths.
量化在伦敦引入每小时20英里（32公里）的交通限速区对道路碰撞、伤害及死亡情况的影响。
基于对1986 - 2006年按地理编码的警方道路伤亡数据进行分析的观察性研究。采用条件固定效应泊松模型，对119029个至少发生过一起伤亡事故的道路路段内道路伤害计数的纵向变化进行分析。针对交通伤亡人数的潜在下降趋势，对引入每小时20英里限速区对这些区域及相邻区域伤亡情况的影响估计进行了调整。
伦敦。
道路碰撞造成的所有伤亡情况；死亡及重伤（KSI）情况。
在对潜在时间趋势进行调整后，引入每小时20英里限速区与道路伤亡人数减少41.9%（95%置信区间为36.0%至47.8%）相关。年龄较小的儿童伤亡人数减少百分比最大，死亡或重伤类别的伤亡人数减少幅度大于轻伤。没有证据表明伤亡事故转移至每小时20英里限速区的相邻区域，这些相邻区域的伤亡人数也平均略有下降，降幅为8.0%（4.4%至11.5%）。结论：每小时20英里限速区是减少道路伤害和死亡的有效措施。
