Publication Details

Evaluation of lane reduction "road diet" measures and their effects on crashes and injuries

Type: Paper

Subtype: HSIS Summary Report

Author(s): Huang, Herman F.; Stewart, J. Richard; Zegeer, Charles V.

Publisher: Federal Highway Administration

Publication Date: 2004

Number: FHWA-HRT-04-082

Address: Washington, DC

Abstract: “ROAD DIETS” ARE OFTEN CONVERSIONS OF FOUR-LANE UNDIVIDED ROADS INTO THREE lanes (two through lanes and a center turn lane), as shown in figure 1. The fourth lane may be converted to bicycle lanes, sidewalks, and/or on-street parking. In other words, existing space is reallocated; the overall area remains the same. Under most average daily traffic (ADT) conditions tested, road diets have minimal effects on vehicle capacity, because left-turning vehicles are moved into a common two-way left-turn lane. However, for road diets with ADTs above approximately 20,000 vehicles, there is a greater likelihood that traffic congestion will increase to the point of diverting traffic to alternate routes.