Cost/Benefit Evaluation of Large Truck-Automobile Speed Limit Differentials on Rural Interstate Highways

Speed differentials between large trucks and automobiles on rural interstate highways are due to both state regulated speed limits and commercial trucking company policies that restrict maximum truck speeds. The initial portion of this effort involved a review of the research and applications literature pertaining to absolute and differential truck speeds on traffic flow, highway safety, and operational costs. Speed data were collected for both heavy trucks and automobiles on rural interstate highways with four speed limit configurations: two with uniform speed limits (75 mph and 70 mph) and two with differential speed limits (70/65 and 65/55 mph). These highways were selected to represent the range of speed limits and posted speed differentials. Stakeholders were surveyed to obtain their opinions as to speed differentials and, more importantly, the basis of those opinions. Surveys were conducted of three stakeholder groups: commercial truck drivers, trucking company safety and operations personnel, and original equipment manufacturers. Using the information from the literature review, the empirical data collected, and stakeholder surveys, a cost-benefit analysis was conducted to address the financial issues related to maximum truck speeds. The information collected, analyzed, and documented in this report will assist both state regulatory agencies and trucking company decision makers when establishing policies related to maximum truck speed limits and speed differentials between heavy trucks and automobiles.