Quantify the effects of raising the minimum speed on rural freeways and the effects of restricting the truck lanes only in the daytime. Volume 1: Evaluating the relevance of 40 mph posted minimum speed limit on rural interstate freeways in Florida.

The relevance of posting the 40 mph minimum speed limit signs on rural Interstate freeways in Florida is analyzed by correlating safety and traffic operating characteristics. The operational data showed that only 0.14% of vehicles had speeds below 40 mph while a 4-year database of reported crashes indicated that about 9% of vehicles involved in crashes were estimated to be traveling with speeds below 40 mph. The modeling of crashes by Poisson regression showed that increase in the median speed significantly reduced the number of crashes while increase in the variation between fast and slow moving traffic significantly increased the number of crashes. The preliminary recommendation that could be made based on the available data is for Florida to discard the practice of posting of minimum speed limit signs on rural Interstate freeways. This recommendation was partly influenced by the survey results which showed that 25 States do not post minimum speed limit signs on highways. (Author/publisher)