Application of Optical Speed Bars to Highway Work Zones

The proximity of workers and traffic makes safety a high priority in highway work zones. The occurrence and severity of accidents is related to vehicle speeds and speed variations. The use of optical speed bars to reduce speeds and speed variations in highway work zones is examined. Previous applications of this traffic control device are considered with respect to design parameters such as length of pattern, number of stripes, and the sequence of spacing between bars. A general design was developed to test the effect of the pattern on speed, the mechanism through which the effect occurs, and the usefulness of the technique to work zones (previous applications have been predominantly at the approach to intersections). Because the application of multiple-pattern designs is impractical, simulations of various designs were developed to obtain subjective evaluations of the relative effectiveness of the various alternatives. Based on the review of previous applications and the subjective evaluations, a pattern design was developed. The design process is delineated and the resulting design described. Also described are adaptations that were made to previous designs specifically for the application of the technique to highway work zones. Finally, a test project to measure the effect of the technique on traffic is described.