Original publication: Removal of Signal Flashing Mode during Late-Night/Early-Morning Operation; FHWA-SA-09-012; 2009 (PDF, 379kB)

For years, it has been standard practice to operate traffic signals in the flashing mode when traffic volumes are low, typically during late-night/early-morning hours. Recognizing that field studies have indicated that crash rates may increase around traffic signals using flashing operations during late-night/early-morning conditions (Source: S.F. Polanis, “Right-Angle Crashes and Late-Night/Early-Morning Flashing Operation: 19 Case Studies,” ITE Journal, April 2002). The City of Winston-Salem, North Carolina was concerned about the high number of crashes at urban signalized intersections operating in the flashing mode during late-night/early-morning hours.

The City of Winston-Salem changed signal operations from flashing mode to steady (stop-and-go) mode during late-night/early-morning hours at 8 intersections experiencing a high incidence of injury crashes, particularly right-angle crashes. The eight intersections ranged in size from one-to-three lanes in each direction, with most being two-lane intersections. All of the intersections had a speed limit of 35 mph (with one 30 mph cross street).

Key Accomplishments

As the Winston-Salem experience demonstrates, removing signals from late-night/early-morning flashing mode operation effectively improves safety and reduces traffic crashes and their resulting injuries.

Results

The removal of the late-night/early-morning flashing mode from eight urban intersections in Winston-Salem cumulatively reduced total crashes by 30.9 percent, injury crashes by 60.1 percent, and right-angle crashes by 88.8 percent per year.

Contact

Stanley Polanis
Director of Transportation
City of Winston-Salem, NC
336-747-6867
stanp@cityofws.org