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原文传递 Speed Limits Set Lower than Engineering Recommendations, Project Summary Report

题名：	Speed Limits Set Lower than Engineering Recommendations, Project Summary Report
作者：	Donnell, E. T.; Gayah, V. G.; Yu, Z.; Li, L.; DePrator, A.
关键词：	Best practices##Highway safety##Traffic control devices##Enforcement##Behavior##Crash data##Data collection##Design speed##Geometric design##Literature review##Operating speed##Speed control##Speed signs##Traffic control##Traffic speed##Travel behavior##
摘要：	The project involved four unique components: a comprehensive literature review, a survey of other state transportation agencies, the collection of speed and safety data from a variety of Montana roadways, and an analysis of these data. Each of these tasks involved the following: (1) The literature review broadly considered the relationships between several speed measures and how these speed measures are associated with safety performance. Further, the review described the relationship between various speed concepts, including the relationship between posted speed limits, operating speeds, and design speeds. Issues related to speed compliance and enforcement were also synthesized. (2) A survey of state transportation agencies was administered to identify current practices with respect to setting speed limits lower than engineering recommendations. The goal of the survey was to determine if other state transportation agencies have experience setting posted speed limits lower than engineering recommendations and, if so, to identify any guidance that might exist for this practice. (3) Vehicle operating speed data were collected at sites (Figure 1) with speed limits set lower than engineering recommendations and at comparable sites with posted speed limits set equal to engineering recommendations for three levels of police enforcement. Statistical tests and regression models were estimated to compare these speed measures and to assess speed compliance at the two site types and compare speed compliance under the various levels of enforcement. (4) The research team used the empirical Bayes (EB) before-after approach to develop crash modification factors (CMFs) that describe the expected change in crash frequency when setting posted speed limits lower than engineering recommendations.
总页数：	4
报告类型：	科技报告