Grade separation of pedestrian and bicycle paths is desirable when traffic volumes and speeds discourage safe crossing of a highway, or railroad tracks, or when necessitated by the crossing of a limited access highway. Cost estimates for underpasses will vary considerably, depending on the geometric requirements of the specific site, method of construction, potential disruption to the surface roadway or rail tracks, and the construction phasing required.

How the Default Unit Cost was Determined

A 100 ft long pedestrian underpass under Route 1 in Woolwich, Maine was built in 1999 for a cost of $400,000 or $4,000 / ft.