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Roadway Speed, <br />• Slower speeds are preferred by pedestrians. <br />• The speed of a vehicle directly impacts the sight distance needed <br />and the braking time of a vehicle. <br />• The speed (S) is used to determine the stopping sight distance. The <br />speed should be the 85th percentile speed of the roadway being <br />crossed. In the absence of collected speed data, it is assumed that <br />the 85th percentile speed is equal to the speed limit. <br />• Slower speeds have been shown to reduce the possibility of a fatal <br />crash in pedestrian/vehicle crashes based on study results by the <br />Washington State Department of Transportation, as shown in the <br />chart below. <br />Impact speeds, pedestrian fatality and <br />injury <br />100% <br />80% <br />60% <br />4 0% <br />20% <br />0% <br />20 trot* 30 mph 40 mph 50 mph <br />xi Fatality X Hwy 0 No injury <br />Roadway Curvature <br />• The vertical and horizontal curvature of a roadway can impact <br />sight lines for both motorists and pedestrians. <br />• For more information on vertical and horizontal curvature, please <br />see the American Association of State Highway and Transporta- <br />tion Officials: A Policy on Geometric Design of Highways and <br />Streets (AASHTO Green Book). <br />SIGHT OBSTRUCTION CAUSED BY ROADWAY CURVATURE <br />Sources: <br />A V. Moudon, L. Lin and P. Hurvitz, "Managing Pedestrian Safety injury Severity," Washington <br />State Department of Transportation, Olympia, WA, February 2007. <br />