Flashing Emergency Lights: Influence of Intensity, Flash Rate and Synchronization on Driver Visibility, Comfort and Confidence
2022-01-0967
03/29/2022
- Event
- Content
- Flashing emergency lights are critical elements of public safety and traffic control during roadway incidents. These lights should not only alert drivers to the presence of hazards, but also should inform them of who and what is present on the scene, and should manage the responses of drivers as they navigate past the incident. First responder and driver safety depends upon all three of these functions. A full-scale outdoor field study was carried out during daytime, during nighttime on dry pavement and during nighttime on wet pavement, using a mock-up scene consisting of three police vehicles parked adjacent to each other. The lights on the vehicles were adjusted to produce different levels of intensity, flash rate, and synchronization of lights across all three vehicles. Upon viewing each combination of these factors, observers in stationary vehicles were asked to identify the location of a silhouette of a police officer randomly placed within the scene and to rate the conspicuity of the lights, their perceptions of glare and what their confidence would be if they were driving past the lights. First responder identification times were shorter at night under the lower intensity, under the slower flash rates and under the synchronized lights. Glare was also reduced at night when the intensity was lower; the slower flash rate on wet pavement also resulted in reduced glare. Higher-intensity lights and faster flash rates were judged as more conspicuous during both day and night conditions. During the daytime, higher intensities gave observers more confidence in driving past the lights. During the nighttime conditions, slower flash patterns resulted in greater confidence. The results build on previous research suggesting that reducing intensity at night and when appropriate, slower and synchronized flashing, can offer safety benefits to both drivers and first responders while improving information to drivers.
- Citation
- Bullough, J., Miller, B., Baker, D., and Rea, M., "Flashing Emergency Lights: Influence of Intensity, Flash Rate and Synchronization on Driver Visibility, Comfort and Confidence," SAE Technical Paper 2022-01-0967, 2022, .