United States Department of Transportation
i
Intersection Geometric Design and Operational Guidelines for Older Drivers and Pedestrians, Volume II: Executive Summary
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1997-05-01
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[PDF-938.64 KB]
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Abstract:This project was performed to develop guidelines for changes in the geometric design and operations at intersections with the greatest potential to aid in their use by older drivers and pedestrians. A literature review identified age-related diminished capabilities that affect performance at intersections, and examined current design standards and their adequacy for older road users. Problem identification studies (accident database analysis, task analysis, focus group discussions, field observations) were conducted to better define older persons' difficulties in intersection use, and an expert panel met to prioritize variables for more extensive laboratory and field studies later in the project. These studies subsequently focused on age (including both young-old and old-old groups) and the effects of opposite left-turn lane geometry (offset amount and direction), right-turn channelization and curb radius, and varying median pedestrian refuge island configurations, using both objective (performance) and subjective measures. A critique of the data obtained in these studies during a second expert panel meeting concluded that sufficient evidence exists to support guidelines for: (1) geometric design to ensure a minimum required sight distance for drivers turning left from a major roadway, and (2) operational changes to accommodate older drivers where (re)design of an intersection to meet sight distance requirements is not feasible. In addition, a revision of Case V in the AASHTO Green Book to determine sight distance requirements that reflect the perceptual task of gap judgment by a left-turning driver more accurately than the current assumptions in Case IIIB is recommended, and further research needs to enhance the safety and mobility of older road users at intersections are identified.
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