- Every year thousands of people are killed or injured in work zone crashes in the US due to excessive speed, distraction, inattentiveness, low visibility, and other factors. Roadway construction and maintenance operations often occur at night when the traffic volume is low, creating less congestion and delay to the traffic. The operations commonly require workers to conduct their work in close proximity to ongoing traffic, and often reduce traffic flow to a single lane while work is undertaken in an adjacent lane. Nighttime brings a reduction in visibility for both workers and drivers. High speed roadways with low visibility and limited protection make an unsafe and dangerous situation for both motorists and workers. Safely controlling and reducing vehicle speeds through work zones decreases the safety risk associated with highway construction and maintenance work. Work zone speed control has been the subject of several research efforts in the past. As such, various techniques and procedures have been tested and evaluated. These include, but are not limited to, variation of traditional fixed signage, changeable message displays, radar units with speed sign messages, and a range of electronic devices to sense and display information related to speed. The present research has been conducted to evaluate the effectiveness of a truck-mounted radar speed sign and additional lighting on speed control during construction and maintenance work. The first phase of the research included evaluating radar speed signs (RSSs) as a speed reduction measure through work zones. RSSs have been known as a way to slow down the traffic flow speed. In this study, the influence of truck-mounted RSSs on vehicle speed for mobile maintenance operation has been tested. In this regard, truck mounted RSSs were employed in two, multi-lane maintenance work zones in the state of Oregon in the US. In each case study, the authors conducted two periods of testing: one with the RSS display turned on (treatment) and one without the RSS display turned on (control), and recorded vehicle speeds. The second phase of the research involved investigating the impact of additional temporary lighting on vehicle speed in highway work zones. In addition, the impact of wearing personal lighting equipment was also examined during paving operations. Two common types of lighting equipment, a light tower and a balloon light, were set up in work zones and a personal, wearable light was used during two paving projects on Oregon highways. Traffic speed and other vehicle and lighting data were collected on different nights when the lighting equipment was turned on and also when it was turned off.Descriptive statistics were used in both studies to summarize collected data and to compare the speed difference between control and treatment cases. The research findings indicate that vehicle speeds are typically lower, and there is less variation in speeds between adjacent vehicles, with the RSS turned on. The results show that the RSS proves to be a promising device for controlling vehicle speed and making the work zones safer for both motorists and workers. Field observations confirmed that both additional temporary roadway lighting and personal lighting help to make workers more visible to motorists and equipment operators. Although a temporary light leads to slightly higher vehicle speeds, it makes the work zone and workers more visible for motorists and equipment operators. Statistical analysis revealed that there is no difference between mean vehicle speed with and without personal lights turned on. Personal, wearable lights are highly recommended for workers who are located away from large equipment and other light sources.The results of this research can be used by DOT Construction and Maintenance Offices for planning construction and maintenance work. The research output can also be used by the Transportation Safety Divisions and Transportation Safety Coordinators within DOTs as a resource for effectively designing work zones and planning construction and maintenance operations.
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