Improving the Effectiveness of Nighttime Temporary Traffic Control Warning Devices, Volume 2: Evaluation of Nighttime Mobile Warning Lights

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 vehicle. 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.Illinois Department of Transportation R27-108published or submitted for publicationnot peer reviewe

Improving the Effectiveness of Nighttime Temporary Traffic Control Warning Devices, Volume 1: Evaluation of Lights on Nighttime Work Zone Channelization Devices

Currently, the Illinois Department of Transportation (IDOT) is one of the few state transportation agencies that require warning lights on nighttime work zone channelization devices, such as drums and barricades. The intent of the steady-burn, amber warning lights is to increase visibility of the channelization devices, providing guidance to motorists and preventing intrusions into the closed lane. However, their additional benefit beyond that provided by the high-reflectivity materials used on the channelization devices themselves has not been evaluated, including taking into consideration their initial, maintenance, and replacement costs; and the environmental and economic issues of routine battery replacement. Applied Research Associates, Inc. (ARA) studied the effectiveness of warning lights on nighttime channelization devices by reviewing pertinent literature, experimental studies of nighttime work zones with and without lights on drums, driver surveys, and focus groups of driver perceptions and behavior in work zones using traffic drums. We applied a cognitive model of driver mental processes to this information to determine the influence of drum warning lights, if any, on driver perception and response. The research showed that, when unprompted, most drivers did not perceive a difference or respond any differently in nighttime work zones using lights on drums than in those without lights. However, when asked to make direct comparisons between work zones with and without lights on drums, there was a slight preference for lights on drums due to the perceived increase in nighttime lighting they provide. Nighttime work zones, and work zones in general, are visually cluttered environments; and the presence (or absence) of lights on drums was not significant enough to attract the drivers’ attention, given competing visual cues such as work zone traffic control devices, other vehicles, and activities in the work space. In addition, the reflective prismatic sheeting on drums in Illinois provides sufficient visibility without warning lights.Illinois Department of Transportation R27-108published or submitted for publicationnot peer reviewe