Title: Modelling Traffic Speeds At Parabolic and Trapezoidal Speed Humps in Jordan

Abstract:-- This research aimed at studying the effect of speed humps on highway traffic speeds and develop models to estimate the hump-crossing speed as a function of the influencing factors. Thirty-one highway speed humps were selected from different areas in Irbid governorate, Jordan. The collected data included area type; posted speed limit; longitudinal slope of the road; road width; presence of speed hump marking; presence of on-street parking; presence of speed hump warning sign and its distance upstream of the speed hump; and speed hump shape (parabolic or trapezoidal), condition, height, and width. The data has also included the upstream and downstream distances from any causes of speed reduction (another speed hump or intersection). Empirical models for estimating hump-crossing speed were developed using regression analysis technique. It was found that parabolic speed humps are more effective in speed reduction than trapezoidal speed humps, and geometric characteristics of speed humps have the highest effect on highway speed reduction. Posted speed limit, presence of speed hump marking, distance of the speed hump warning sign upstream of the speed hump, speed hump condition, speed hump width, and speed hump width to height ratio variables were directly proportional with hump-crossing speed. On the other hand, the distance to the nearest speed hump or intersection upstream of the speed hump, presence of speed hump warning sign, speed hump height, speed hump height to width ratio, and upstream ramp slope variables were inversely proportional with hump-crossing speed.