Warning lights on service vehicles in moving and short-term workzone operation serve as part of and sometimes as the primary traffic control scheme. This paper reports on a study examining driver information neeeds in these work zone situations, the impact of various warning light parameters on selected driver behaviors and the effectiveness of several warning light systems in short-term and moving work zone operations. Various lighting systems (i.e., strobes, rotating lights, flashing lights and a light bar) were field tested. Closed test track results indicated that certain characteristics (e.g., flash rate, number of lights, medium versus high intensity) had little effect on driver closing rate and speed estimating performance. These tests confirmed the importance of information transmission (e.g., directional arrow) in addition to conspicuity. Test track findings also demonstrated that the slower the maintenance vehicle travelled, the more difficulty drivers had in judging closing rate when approaching the rear of the service vehicle. Actual highway observations were conducted in simulated maintenance activities in three states. Results obtained for stationary short-term lane closures suggest use of rotating light and flashing light combinations on service vehicles. Arrow boards were effective for lane closures. For moving maintenance operations the rotating light plus flashing light, the Ohio (two headlight size lights in a flashing mode) light and the light barwere most effective. However, the light bar was not as effective instationary operations. Again, arrow boards were also effective. While a shadow vehicle following a moving maintenance operation at 500 feet was highly effective, it was considered optional due to its expense. A simple cost-benefit model was developed to help decide when shadow vehicle use was warranted. The product of this research was guidelines for warning light use on service vehicles in eleven categories of short-term and moving work zone operations.
Abstract