This research was conducted primarily to determine the relationships between hump spacing and the speed selection of isolated vehicles in residential street environments. The speed profile of each of the observed isolated vehicle was used to determine the speed selection patterns of drivers in selecting their speed within a given road hump interval. The effect of hump spacing and its relationship with average speed, 85th and 95th percentile speed and maximum speed were analyzed using linear regression technique. Similarly, the relationships of the geometric design of road humps on post entry speed, and the post entry speed to maximum speed were also examined. The plot of the speed profile of isolated vehicles indicated some behavioral patterns driver select their speed. This study indicated that approximately 80% or more of the vehicles traveling within a hump interval of 48m and 178m the apparently reached their peak speed within the third quarter of the hump spacing. Results of the regression analysis shows that hump spacing appear to be a strong explanatory variable for maximum speed attained of isolated vehicles. It was also indicated that as road hump spacing is increased from 48m to 178m the 85th and the 95th percentile would also increase from 37km/h to as high as 56km/h and 62km/h respectively. The slope of the line of the generated model of the 85th and the 95th percentile speed versus hump spacing indicates that drivers are less sensitive to the residential street environment specifically to pedestrian's safety.
