The objective of this research was to determine the effectiveness of various alternative strategies for reallocating the usage of street width on urban arterials without changing the total curb-to-curb width. The research evaluated improvement strategies for urban arterial streets with curb-and-gutter cross-sections and speeds of 45 mph or less. The design alternatives that were evaluated ranged from a two-lane undivided cross-section to cross-sections with as many as eight lanes for through traffic. Evaluations were performed of the safety effectiveness of 35 improvement projects that involved use of lane widths of 10 ft or less. Field observations of passenger car and truck operations on selected sites were also conducted. The evaluation concluded that improvement strategies that involve installation of a centre two-way left-turn lane are likely to reduce accident rates even when narrower lanes for through traffic must be used. Improvement strategies to provide additional through lanes without the addition of a two-way left-turn lane may increase intersection accidents, but generally do not affect midblock accidents. None of the strategies involving narrower lanes affected accident severity. The report includes a recommended process for selecting appropriate improvement strategies for urban arterials based on their traffic operational and safety effects. Guidelines for implementation and evaluation of projects are presented. (A)
Abstract