详情

原文传递 Speed Limits Set Lower than Engineering Recommendations

题名：	Speed Limits Set Lower than Engineering Recommendations
作者：	Donnell, E. T.; Gayah, V. G.; Yu, Z.; Li, L.; DePrator, A.
关键词：	Best practices##Highway safety##Travel behavior##Enforcement##Behavior##Crash data##Data collection##Design speed##Geometric design##Literature review##Operating speed##Speed control##Speed signs##Traffic control##Traffic control devices##Traffic speed##
摘要：	The purpose of this project is to provide the Montana Department of Transportation (MDT) with a better understanding of the operational and safety impacts of setting posted speed limits below engineering recommended values. This practice has been performed on Montana roadways for a variety of reasons but the safety and operational impacts are largely unknown. An Empirical Bayes observational before-after study found that there is a statistically significant reduction in total and fatal and injury crashes at sites with engineering speed limits set 5 mph lower than engineering recommendations. At locations with posted speed limits set 10 mph lower than engineering recommendations, there was a decrease in total crash frequency, but an increase in fatal and injury crash frequency. The safety effects of setting posted speed limits 15 or 25 mph lower than engineering recommendations is less clear, because the results were not statistically significant, due to the small sample size of sites available for inclusion in the analysis. An operating speed evaluation found that, when the posted speed limit was set only 5 mph lower than the engineering posted speed limit, drivers tend to more closely comply with the posted speed limit. Compliance tends to lessen as the difference between the engineering recommended posted speed limit and the posted speed limit increases. The practice of light enforcement, which was defined as highway patrol vehicles making frequent passes through locations with posted speed limits set lower than engineering recommendations, appeared to have only a nominal effect on vehicle operating speeds. Known heavy enforcement, defined as a stationary highway patrol vehicle present within the speed zone, reduced mean and 85th-percentile vehicle operating speeds by approximately 4 mph.
总页数：	127
报告类型：	科技报告