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Date of Award
Civil and Environmental Engineering
Timothy J. Gates
EVALUATING THE USE OF
STEADY BURN WARNING LIGHTS ON DRUMS
FOR WORK ZONE SAFETY
PRASAD LAKSHMI VARA NANNAPANENI
Advisor: Dr. Timothy Gates
Major: Civil Engineering
Degree: Doctor of Philosophy
Roadway maintenance and repair has become increasingly commonplace in the United States over the past several decades as our roadway infrastructure has continued to age and deteriorate. Maintenance and repair work on an existing roadway often presents the challenge of maintaining traffic on the existing roadway while work is being performed, thereby necessitating the use of what is commonly referred to as a roadway "work zone". One of the most important components of traffic control in a work zone is delineation of the edge of the traveled way, which assists drivers with tasks such as: lane selection; lateral positioning within a lane; and speed control. Delineation of the edge of the traveled way is commonly provided by a series of portable devices, such as drums, cones, vertical panels, or barricades. The type and duration of the work being performed often requires that these channelizing devices remain in place at all times.
Maintaining traffic through nighttime work zones poses increased risks for drivers and roadway workers due to the lack of ambient light. To help overcome nighttime visibility issues, the 2009 Manual on Uniform Traffic Control Devices (MUTCD) requires work zone traffic control devices to be retroreflective or internally illuminated. To help supplement retroreflectivity, Section 6F.81 of the 2009 MUTCD allows for the use of auxiliary steady burn warning lights (SBWL) on work zone channelizing devices.
Until recently, plastic drums with steady burn warning lights had been the primary channelizing device utilized in work zones throughout the State of Michigan for several years. However, the use of sheeting materials with improved retroreflectivity, including high intensity and microprismatic (i.e., prismatic) materials, has prompted investigation into the value and effectiveness provided by the steady burn warning lights. Furthermore, although previous research has explored the effectiveness of steady burn warning lights on drums both in Michigan and elsewhere, these efforts included a relatively limited number of work zone sites and/or focused on controlled human factors experiments. As a result, research was undertaken to explore the impacts associated with the use of steady burn warning lights on channelizing drums considering a variety of work zone scenarios utilized in Michigan.
The primary goal of this research was to evaluate the safety impacts associated with the use of steady burn warning lights on drums in roadway work zones in Michigan. The following research objectives were addressed in this study:
1. Determine the state-of-the-art of work zone channelization through a comprehensive literature review.
2. Determine the state-of-the-practice regarding the use of steady burn warning lights by roadway agencies throughout the United States.
3. Assess the crash experiences of states with respect to the work zone steady burn warning light policy or practice.
4. Evaluate the impacts that steady burn warning lights on channelizing drums have on work zone crash occurrence in Michigan.
5. Evaluate the driver behavioral impacts associated with the use of steady burn warning lights on channelizing drums in Michigan work zones.
6. Determine the degree by which steady burn warning lights affect the overall brightness of work zone drums in Michigan.
7. Assess the overall impacts of steady burn warning lights on work zone safety.
A comprehensive research methodology was developed to address these objectives. The initial tasks involved a comprehensive review of the current state-of-the-art and a state DOT survey related to the use of drums or other channelizing devices in roadway work zones, both with and without the presence of steady burn warning lights. The next tasks involved a comparison of work zone crash trends, both among states with varying policies on the use of steady burn warning lights, as well as a detailed investigation of crash data for work zones within the State of Michigan. To further supplement the crash data, a series of field studies were performed at 36 Michigan work zones to provide a more in-depth evaluation of differences in driver behavior and performance with respect to the use of steady burn warning lights. In addition to these field studies, a series of luminance tests were also conducted to assess the relative brightness levels provided by drums with and without warning lights. The luminance tests were performed both in the field and in a controlled environment to gauge the impacts of steady burn warning lights on drum visibility.
Established sampling procedures were utilized to determine the target sample sizes necessary to assess statistical inference on the measures of effectiveness (MOEs). The data were collected for each study component under a variety of representative field conditions, which included different types of roadways, work zone configuration, levels of ambient lighting, roadway geometry, and other factors. Each of the MOEs were analyzed using appropriate statistical techniques to determine the impacts of steady burn warning lights and the impacts of other factors.
The results showed that the presence of steady burn warning lights on work zone channelizing drums increased the occurrence of risky driver behavior, as evidenced by a higher proportion of drivers traveling too close to the drums, more frequent steering reversals, and higher vehicular speeds. These findings were further substantiated by the observance of a greater proportion of damaged drums at work zone locations with steady burn warning lights.
Steady burn warning lights were not found to provide substantial increases to the luminance of the drums either in the field or in a controlled environment. It was determined that the use of microprismatic sheeting materials provide considerably greater luminance increases for the drums compared to the addition of a steady burn warning light to the drum.
The state DOT survey revealed that only approximately one-third of the 42 responding state agencies utilize steady burn warning lights on channelizing devices in work zones and only one-tenth of the responding agencies utilize them on a frequent basis. The majority of agencies that use steady burn warning lights do so on an infrequent basis, typically for specific types of applications, such as at spot hazards, tapers, lane shifts, and crossovers.
The investigation of nationwide work zone crash statistics revealed only slight differences between the rates of work zone crashes for the various steady burn warning light usage practices. The states that frequently use lights on drums exhibited a slightly higher aggregate work zone crash rate, while the states that infrequently use lights on drums had the lowest aggregate crash rate. No discernable differences were observed between any of the three groups of states when examining work zone crashes as a proportion of total crashes.
A detailed review of Michigan work zone crash statistics revealed that a higher proportion of work zone crashes tended to occur during nighttime conditions at locations with steady burn warning lights compared to locations without steady burn warning lights. Deeper investigation showed that among those crashes occurring in the presence of drums, the proportion of the crashes that may have been affected by the drums was indistinguishable between the two samples.
Based on a synthesis of all results, steady burn warning lights demonstrate no substantive value to nighttime brightness, driver behavior, or crash prevention when used on channelizing drums in work zones. Thus, it was concluded that steady burn warning lights demonstrate no additional safety benefit when used on channelizing drums in work zones. Furthermore, steady burn warning lights may actually contribute to a greater crash risk due to the increase in risky driver behavior that was observed when steady burn warning lights were present.
Drums with high intensity sheeting that is in good condition will provide adequate nighttime brightness for work zone channelization regardless of whether a steady burn warning light is attached or not. Therefore, it is recommended that the use of steady burn warning lights on work zone drums be discontinued. If additional nighttime brightness of the channelizing devices is desired, the use of microprismatic sheeting on the drums provides far greater increases in brightness than the addition of a steady burn warning light.
Nannapaneni, Prasad, "Evaluating the use of steady burn warning lights on drums for workzone safety" (2011). Wayne State University Dissertations. Paper 250.