Wagenaar A C, Streff F M, Schultz R H
Division of Epidemiology, School of Public Health, University of Minnesota, Minneapolis 55455.
Accid Anal Prev. 1990 Dec;22(6):571-85. doi: 10.1016/0001-4575(90)90029-k.
Effective December 1987 and January 1988, the maximum speed limit on rural limited access highways in Michigan was raised from 55 mph to 65 mph. This study examined the effects of the raised limit on injury morbidity and mortality. A multiple time-series design was used, comparing roads where the speed limit was raised with roads where the limit remained unchanged. Data were collected on numbers and rates of automobile crashes, injuries, and deaths from January 1978 through December 1988. Time-series intervention analyses were conducted to estimate effects associated with the speed limit change while controlling for long-term trends, seasonal cycles, and other patterns. Statistical controls were also included for major factors known to influence crash and injury rates. Results revealed significant increases in casualties on roads where the speed limit was raised, including a 19.2% increase in fatalities, a 39.8% increase in serious injuries, and a 25.4% increase in moderate injuries. Fatalities also increased on 55 mph limited access freeways, suggesting that the 65 mph limit may have spillover effects on segments of freeways where the limit was not changed. No significant changes in fatalities or injuries were found on other types of roads. The increased convenience of reduced travel time with the higher speed limit is obtained at a significant cost in terms of injury morbidity and mortality.
1987年12月和1988年1月起，密歇根州农村限制进入高速公路的最高限速从每小时55英里提高到每小时65英里。本研究考察了限速提高对伤害发病率和死亡率的影响。采用多重时间序列设计，将限速提高的道路与限速不变的道路进行比较。收集了1978年1月至1988年12月期间汽车碰撞、受伤和死亡的数量及发生率数据。进行了时间序列干预分析，以估计与限速变化相关的影响，同时控制长期趋势、季节周期和其他模式。还对已知影响碰撞和伤害发生率的主要因素进行了统计控制。结果显示，限速提高的道路上伤亡人数显著增加，包括死亡人数增加19.2%，重伤人数增加39.8%，中度受伤人数增加25.4%。在限速每小时55英里的限制进入高速公路上死亡人数也有所增加，这表明每小时65英里的限速可能对限速未改变的高速公路路段产生溢出效应。在其他类型的道路上未发现死亡或受伤人数有显著变化。以伤害发病率和死亡率为巨大代价，换来了因更高限速而减少出行时间所带来的更多便利。
