Research on Effectiveness of Freeway Work Zone Speed Reduction Strategies

Two-lane, one-way freeways compose a large percent of the freeway system nationwide. Preserving, expending, and enhancing these freeways result in many work zones which have caused a safety concern for the traveling public. Aimed at reducing crashes attributed to the existence of these work zones, an evaluation of speed reduction measures was carried out in work zones of the freeway. The speeds before and after three speed reduction strategies were measured. The mean and 85 percentile speed, and the standard deviation of the speed were analyzed statistically. It can be concluded that the effect of the individual warning sign was very limited, which can not achieve the desired results. However, the three dimensional speed markings made sense, which can reduce the mean speed by 10.4 km/h; but in the meantime the standard deviation of the speed increased because many drivers misunderstood it, got confused or braked a vehicle suddenly. Besides, the effect of the speed limit sign with camera graph was very obvious, which made the mean speed slow down by 17.3 km/h, and standard deviation of the speed fell as well. So the speed limit sign with camera graph could be used in the work zones of the freeway to control the speed while the warning sign, and the three dimensional speed markings were not recommended. Keywords-Work zone, Traffic safety, warning sign, Three dimensional speed markings, Speed limit sign with camera graph.