|Abstract:||Vehicle-mounted warning lights for nighttime mobile highway operations provide critical protection to workers and the driving
public. Alerting the traveling public of the approaching work activity and providing guidance is vital to maintaining safety and
mobility. Previous research conducted for IDOT on mobile lane closures (Steele and Vavrik 2009) identified driver confusion
as a concern to the safety of nighttime highway operations. Users are subject to warning lights from multiple agencies with
varying characteristics and configurations, but we know little about driver comprehension of these signals and their influence
on driver behavior.
Applied Research Associates, Inc. (ARA) studied the effectiveness of warning lights on nighttime highway operations,
including mobile lane closures, incident responses, and police activities, by reviewing pertinent literature, performing
observational and experimental field studies, and conducting driver surveys and focus groups of driver perceptions and
behavior in response to nighttime mobile operations. We used a cognitive model of driver mental processes to analyze this
information and better understand the interaction between warning lights and driver perception and behavior, and to identify
and evaluate potential improvements to current practice.
The research showed that drivers view current vehicle-mounted warning lights as highly visible, attention-getting, and
effective at conveying the message caution/alert. However, intense lights can cause discomfort glare and multiple light sets
on individual vehicles, or multiple vehicles at a location, can be distracting, annoying, or anxiety-inducing. Complex visual
scenes can confuse drivers and take longer to process cognitively, leading to slower reaction times. Often, information
provided by flashing arrows, signs, and changeable message signs can be interfered with by other warning lights on the same
Suggestions for improvement from the focus groups centered primarily on reducing the number of flashing lights, or
synchronizing their flashing, on individual vehicles, reducing the intensity of specific lights, sequential flashing of arrows
between multiple trucks in a convoy, and incorporating directional motion in light bars. Researchers were not able to test
some of the ideas due to limitations of current device technology; however, field experiments on several suggested concepts
showed the potential to improve driver perception, comprehension, and behavior by modifying the number, intensity, and
synchronization of lights on individual vehicles, as well as between vehicles.