Through traffic in work zones at night poses challenges as a result of diminished visibility. The Manual on Uniform Traffic Control Devices (MUTCD) requires traffic control devices, including those in work zones, to be retroreflective or internally illuminated (1). Although the 2009 MUTCD sets out minimum in-service retroreflectivity values for road signs, such standards are not provided for other devices commonly used in work zones, such as pavement markings, delineators, and channelizing devices (1). The MUTCD does state in Section 6F that work zone devices shall be replaced that are damaged, or have lost a significant amount of their retroreflectivity (1). One of the most important components of work zone traffic control is delineation of the edge of the travel way, a function that is commonly performed by using devices to channelize traffic. Such devices in work zones provide drivers with critical information about an upcoming road condition (e.g., lane or shoulder closure, taper, lane shift, narrowed travel way, separation of opposing traffic), which may require a responsive maneuver. Work zone devices that channelize traffic are particularly important to assist drivers with maneuvers such as lane selection, lateral positioning within a lane, and speed control. Because of the dynamic nature of work zones, portable, temporary devices (drums, cones, and vertical panels) typically are used to control traffic. To help supplement retroreflectivity, Section 6F.81 of the 2009 MUTCD allows for the use of auxiliary lights on work zone channelizing devices, although these lights must typically be steady burning when placed on a series of such devices (1). Roadway agencies throughout the United States have used steady- burn warning lights on devices used to channelize traffic in work zones for many years, although the use of brighter sheeting materials has prompted investigation into the value of such lights (2). Crashes in nighttime work zones generally are rare, primarily because of the relatively short duration and length of most work zones, coupled with drivers’ perception of elevated risk when they travel through them. The transient nature of work zones makes it difficult, furthermore, to identify causal relationships between various work zone characteristics and crash occurrences. Other measures of effectiveness (MOEs), such as those related to nighttime driver behavior or visibility, are used as surrogates to assess the potential safety-related benefits of work zone traffic control devices. Such surrogate MOEs may include • Lateral lane placement of vehicles, • Erratic maneuvers, • Steering reversals, • Encroachment on to the centerline or edgeline, • Vehicular speeds, Impact on Driver Behavior of Steady-Burn Warning Lights on Channelizing Drums in Work Zones Timothy J. Gates, Peter T. Savolainen, Tapan K. Datta, and Prasad Nannapaneni 25 Research was performed to explore the impact on driver behavior of steady-burn warning lights on drums used in highway work zones in the state of Michigan. Various characteristics related to nighttime driver behavior were evaluated with data collected in actual work zones. Thirty-six randomly selected work zones in 15 counties throughout lower Michigan were investigated in this study. Collectively, the work zones represented a broad range of commonly occurring scenarios. Work zones that used drums with steady-burn warning lights and work zones that did not were examined in a comparative parallel study. Data on nighttime driver behavior were collected by recording the movements of randomly selected subject vehicles as they were followed by a survey vehicle through the study work zones. For each subject vehicle, three measures of driver behavior were collected. The measures were (a) percent of time spent in the center lane position, (b) percent of time spent in the lane position closest to the drums, and (c) rate of steering reversals per minute. The data were compared by using analysis of variance techniques. The results showed that the presence of steady-burn warning lights on drums used to channelize traffic in work zones did not significantly affect either the time vehicles spent in the center lane position or the rate of steering reversals. The presence of steady-burn warning lights did, however, increase the tendency of drivers to travel in relatively close proximity to the drums. Collectively, the research findings suggest that the use of steady-burn warning lights on channelizing drums in work zones does not have a substantive impact on nighttime driver behavior. Roadway work zones have become increasingly commonplace in the United States over the past several decades. By the 1980s, most of the nation’s roadway system had been built. Ever since then, an increasing percentage of road work has involved the maintenance and repair of deteriorating infrastructure built during the previous decades. Maintenance and repair work presents the challenge of either main- taining or rerouting traffic elsewhere while work is performed. Capacity limits, or the lack of alternate routes, often necessitate that traffic remain on the roadway while work is performed. Although most road work in Michigan is performed during the day, its type and duration usually require traffic controls to remain in place at all times. Department of Civil and Environmental Engineering, Wayne State University, Engi- neering Development Center, Room 0504, 5050 Anthony Wayne Drive, Detroit, MI 48202. Corresponding author: T. J. Gates, tjgates@wayne.edu. Transportation Research Record: Journal of the Transportation Research Board, No. 2258, Transportation Research Board of the National Academies, Washington, D.C., 2011, pp. 25–31. DOI: 10.3141/2258-03