Effects of Warning Lamp Color and Intensity on Driver Vision

The work reported here was part of a program of research on how warning lamps affect driver vision, and how those lamps can be designed to provide the most benefit for the safety of emergency vehicle operations. In order to understand the overall effects of lamps on safety, it is necessary to know about the positive (intended) effects of the lamps on vehicle conspicuity, as well as any negative (unintended) effects that the lamps may have on factors such as glare and driver distraction. This research was designed to provide information about how the colors and intensities of warning lamps influence both positive and negative effects of such lamps, in both daytime and nighttime lighting conditions. Color and intensity have received considerable attention in standards covering warning lamps (e.g., SAE, 2004, 2005), and interest in these variables has recently increased because of the new options provided by the growing use of LED sources in warning lamps. Participants in this study were selected to be reasonably representative of the driving public. Two groups, based on age, were chosen to insure that some estimate could be made of how warning lamp effects might change with driver age. A static field setting was used to simulate the most important visual circumstances of situations in which drivers respond to warning lamps in actual traffic. Two vehicles with experimental warning lamps were placed so that they would appear 90 degrees apart in a simulated traffic scene as viewed by an experimental participant who was seated in a third vehicle. Four lamp colors were used (white, yellow, red, blue), and all four colors were presented at two levels of intensity. All intensity levels were high relative to current minimum requirements, since the greatest interest was in measuring potential benefits of high intensity lamps in the day, and possible problems with high intensity lamps at night. Participants performed three tasks, under both day and night conditions: 1. Lamp search, in which the participant had to indicate as quickly as possible whether a flashing lamp was present on the right or left simulated emergency vehicle. This task was designed to capture the kind of visual performance that would be important when a driver tries to locate an emergency vehicle approaching an intersection on one of two possible paths. Faster performance for a certain type of lamp can be taken to mean that the lamp provides better conspicuity. 2. …