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Pedestrian Overpasses/Underpasses:

Pedestrian overpasses and underpasses allow for the uninterrupted flow of pedestrian movement separate from the vehicle traffic. However, they should be a measure of last resort, and it is usually more appropriate to use traffic-calming measures or install a pedestrian-activated signal that is accessible to all pedestrians. This is also an extremely high-cost and visually intrusive measure.

Such a facility must accommodate all persons, as required by the ADA. More information on the specifications for accessing overpasses and underpasses can be found in the Draft Guidelines for Accessible Public Rights of Way.4 These measures include ramps or elevators. Extensive ramping will accommodate wheelchairs and bicyclists, but results in long crossing distances and steep slopes that discourage use.

Studies have shown that many pedestrians will not use an overpass or underpass if they can cross at street level in about the same amount of time.8, 9 Overpasses work best when the topography allows for a structure without ramps (e.g., overpass over a sunken freeway). Underpasses work best when designed to feel open and accessible. Grade separation is most feasible and appropriate in extreme cases where pedestrians must cross roadways such as freeways and high-speed, high-volume arterials.

Photo by Yan Jia
This pedestrian overpass takes advantage of existing topography and allows pedestrians to avoid conflicts with traffic at street level.

• Provide complete separation of pedestrians from motor vehicle traffic.
• Provide crossings where no other pedestrian facility is available.
• Connect off-road trails and paths across major barriers.
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• Use sparingly and as a measure of last resort. Most appropriate over busy, high-speed highways, railroad tracks, or natural barriers.
• Pedestrians will not use if a more direct route is available.
• Lighting, drainage, graffiti removal, and security are also major concerns with underpasses.
• Must be wheelchair accessible, which generally results in long ramps on either end of the overpass.
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  Estimated Cost
$500,000 to $4 million, depending on site characteristics.
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