Mode of Flashing for Malfunctioning Traffic Signals

This paper presents the analysis of traffic operations at 34 instances of yellow/red malfunction flash and nine instances of red/red malfunction flash in the Atlanta area. Malfunction flash occurs when a traffic signal’s malfunction monitoring unit detects a problem and automatically initiates a flashing operation. Many of these instances were during periods of high demand, and a high level of driver confusion was documented. The stopping rate of major-street through drivers (i.e., those facing a flashing yellow signal and not required to stop) exceeded 75% at some yellow/red flash intersections. This eliminates many of the operational benefits that yellow/red flash is generally assumed to have over red/red flash and may create a safety hazard. To predict major-street (flashing yellow) stopping rates, logit models were developed. At red/red flash intersections, 10–20% of drivers did not stop before entering the intersection; many of these drivers crept through or “piggybacked” with another vehicle.