Dynamic Speed Monitoring, Dangerous Curves


The design of rural interchanges is of critical concern due to the need for the safe transition of vehicles from one high speed roadways to another and vice versa. This transition is accomplished by entry and exit ramps of various forms. The southbound entry loop ramp at the US 27/ US 192 trumpet interchange in Polk County, Florida does not provide such safe transition since historically there has been a high incidence of vehicular off-tracking. The geometry of the southbound entry ramp coupled with high approach speeds are two of the contributing factors. Due to the high cost of interchange modification and ramp realignment, one approach to increasing safety at the interchange is to decrease approach speeds (assumes that speed is a surrogate measure of safety) utilizing a Dynamic Speed Monitoring (DSM) system. The objective of this thesis was to test the effectiveness of such a DSM system at reducing vehicle speeds at the rural US 27/ US 192 trumpet interchange in Polk County, Florida. The system tested was a solar powered, radar based, wireless speed warning system which potentially could be used at traffic locations where it is difficult to secure power and to extended wires. The Measures of Effectiveness (MOEs) for the system were the reduction in mean and variance of speed along with the proportion of vehicles in the higher speed ranges after system implementation. This thesis describes the testing of the DSM effectiveness and involves the documentation of the experiments conducted, the data collected and the analysis of the results. Speed data was collected Before and After installation of the DSM system at two points preceding the southbound entry ramp. Approach speeds were collected at a point 250 feet in advance of the southbound entry ramp curve (also the detection zone of the DSM system radar) and PC speeds were collected at the Point of Curve of southbound entry ramp. Various data sets were analyzed in order to ascertain the systems effectiveness during the day and night, weekdays and weekends, various time periods during the day, and within various speed ranges. The Approach and PC data analysis indicated that the DSM system significantly (at the 95% confidence level) reduced speed mean and variance and increased speed limit/ advisory speed compliance. The Approach mean speed was reduced by 3.58 mph and the PC mean speed was reduced by 1.57 mph. The Approach speed variance was reduced by 3.34 and the PC speed variance was reduced by 0.70 mph. Approach speed limit compliance was increased by 22.27% and PC advisory speed (35 mph) + 5 mph compliance was increased by 11.56% (it was apparent that motorist were utilizing speeds above the advisory speed to navigate the curve). In general, the effectiveness of the DSM system was diminished on weekends as well as during the late night and early morning (12 AM to 7 AM) time periods. This suggested that when there were lower volumes and when motorists' perceived that speed limit enforcement was not as likely, the DSM system effectiveness was reduced. The DSM system resulted in a reduction in the percentage of vehicles utilizing the higher speed ranges (≥ 45 mph). There was a 62% average reduction in the vehicles that utilized the speed ranges above 57 mph for the Approach data and there was a 36% average reduction in the vehicles that utilized the speed ranges above 45 mph for the PC data. The DSM system resulted in a shift in the distribution of speeds from the higher speed bins to the lower speed bins Before and After installation.


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Graduation Date





Oloufa, Amr


Master of Science (M.S.)


College of Engineering and Computer Science


Civil and Environmental Engineering

Degree Program

Civil Engineering








Release Date

December 2007

Length of Campus-only Access


Access Status

Masters Thesis (Open Access)