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si <br />Principle No. 1: Street Width <br />Figure 1.1: Relationship Between Street Width and Accidents in Longmont, Colorado based on Swift, et <br />al., (1998) <br />Accidents /Mile/Year <br />12 <br />10 <br />8 <br />6 <br />4 <br />2 <br />0 <br />III Wig <br />20 22 24 30 32 34 36 38 40 <br />Street Width (ft) <br />42 <br />44 <br />46 <br />48 <br />50 <br />The curve illustrates the increase in the number of accidents as street width increases. <br />CASE STUDY: PORTLAND, OREGON <br />(Source: Portland Office of Transportation, 1994) <br />The City of Portland investigated the use of queuing streets as described by ASCE (1990) to reduce street <br />widths. The ASCE design assumes that cars will wait between parked cars, or "queue ", while the <br />approaching traffic passes (see Figure 1.2). The new design reduces existing street widths by up to eight <br />feet. Prior to implementing the revised standard, the Portland Department of Transportation studied <br />existing narrow streets to determine if reduced street widths would endanger pedestrians and residents. <br />The findings of this study were: <br />• A bicycle and a car can fit down a 24 foot wide street with parking on both sides. <br />• A dump truck can fit down a 24 foot wide street with parking on both sides. <br />• Fire trucks can easily drive down 26 foot wide streets with parking on both sides. <br />• A fire truck can make the turn from an 18 foot wide to a 20 foot wide road at slow speeds. <br />• Traffic engineers could point to no accident history relating to narrow street widths. <br />- 33 - <br />