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原文传递 Road Diet Conversions: A Synthesis of Safety Research

题名：	Road Diet Conversions: A Synthesis of Safety Research
作者：	Thomas, L.
关键词：	Road diet conversions##Safety research##Safety effectiveness##Traffic lane reduction##Motor vehicle crashes##Vehicle accidents##Methodologies##Table (Data)##
摘要：	The primary purpose of this review is to assess the available evidence regarding the safety effectiveness of reductions in the number of motorized traffic lanes, widely known as road diet conversions. Although road diets have been implemented since at least the 1970s, earlier reviews and a search of the literature identified no controlled safety evaluation studies conducted prior to the year 2002. A systematic search of literature dating from 2002 was conducted. Six studies in total were initially identified, with four serving as the basis for most conclusions in this review. Several of the studies have used overlapping data from many of the same implementation sites, with the more recent studies employing the more robust study methodologies. As a result, the strongest evidence comes from relatively few studies building on earlier ones. However, a sizeable number of sites have been encompassed in the studies. Studies using data from sites in California, Iowa, and Washington provide the strongest evidence of safety effects, with additional reports providing corroborating, but somewhat weaker evidence. Road diets can be seen as one of the transportation safety field’s greatest success stories. Total crashes might be expected to decline by an average of29 percent by converting from four, undivided lanes to three lanes (plus other uses such as bike lanes). Additionally, the studies determined total crash reductions were higher (47 percent) for treated sections of more rural thoroughfares passing through smaller towns (Iowa sites) and lower (19 percent) for road diet corridors in large urban areas (California and Washington sites) (Harkey et al., 2008). Thus far, only a single study from New York City has examined effects on pedestrian crashes (Chen et al., 2013). Although the researchers were unable to use the most robust methodology due to a lack of traffic volume data, the inclusion of 460 road diet sites and large number of comparison locations supports the findings of significant reductions in total crashes, significant reductions in injurious and fatal crashes, and a trend of lower pedestrian crashes at segments. Total crashes and injurious crashes also declined significantly at intersections abutting the road diet sections. Each potential road diet should be vetted on a case by case basis. Case study and modeling results suggest that added caution is warranted before implementing road diets when volumes approach 1,700 vehicles per peak hour or are in the range of 20,000 to 24,000 vehicles per day (HSIS, 2010; Knapp and Giese, 2001; Welch, 1999). However, high quality disaggregate estimates of safety effects of road diets for different volume roadways are lacking. Further study of potential traffic and safety effects on surrounding roads and access from side streets to the road diet corridor may also be needed.
总页数：	17
报告类型：	科技报告