Service Vehicle Lighting and Traffic Control Systems for Short-Term and Moving Operations

This project applied laboratory, test track, and highway field study to develop traffic control systems for short-term and moving maintenance operations. While the emphasis of this study was to test vehicle lighting system effectiveness, developed guidelines included use of ground-mounted signs and supplemental flags. The first project step analyzed driver information requirements and produced a categorization of short-term and moving operations. Secondly, laboratory testing established driver understanding of specific service vehicle markings intended to advise of maintenance convoys. Black diagonal stripes on an orange background and borders of alternating red and white blocks were found to be effective. Various lighting systems (i.e., strobes, rotating beacons, flashers, 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 no effect. These tests confirmed the importance of information transmission (e.g., directional arrow) over conspicuity. Test track findings also demonstrated that slower maintenance vehicles were more difficult for drivers to judge. Actual highway observations were conducted in simulated maintenance activity in three states. Results obtained for short-term lane closures recommended rotating beacon and flasher combinations on service vehicles and warning signs mounted 1 to 1 1/2 ft above the pavement at advance distances of 1500, 1000, and 500 ft. The light bar was found effective in moving maintenance operations. While a shadow vehicle following a moving maintenance operation at 500 ft was highly effective, it was considered optional due to its expense. (A preliminary cost-benefit analysis suggests economic justification if the shadow vehicle can be shown to eliminate 3-6 injury/PDO accidents per year or one fatality in 16 years.) The field study also found orange flags on ground-mounted signs and orange cone tapers to be effective as worker protection in shoulder closure maintenance activity. The product of this research is traffic control guidelines for eleven categories of short-term/moving work zone.