Evaluation of Truck Operating Characteristics on a Rural Interstate Freeway with Median Lane Truck Restriction

The increase in truck traffic on interstate freeways continues to raise concerns about the large trucks’ dimensions that cause sight distance problems and about trucks’ low capability to accelerate, decelerate, and maintain speed particularly on steep grades. To address safety and operational concerns caused by truck traffic, a multitude of restriction policies have been instituted around the United States. This study was aimed at determining the operational and safety impacts of the 24-h restriction of trucks from using the median lane of a six-lane freeway corridor, Interstate 75 in Florida. It should be noted that traffic flow on this corridor is relatively uncongested and the corridor operates at Level of Service B or better throughout the day. Analysis of field and simulation data indicated that the difference between truck and passenger car speeds and travel times were insignificant on the unrestricted middle and shoulder lanes. About two-thirds of both passenger cars and trucks were traveling within the 10-mph pace that ranged from 70 to 80 mph in the corridor, which has a speed limit posted at 70 mph. The field data also indicated that trucks were able to use the middle lane to pass 25% of the time during the truck peak-hour period with the assumption of a 10-s gap acceptance. In addition, simulation analysis indicated that opening all lanes to trucks increased the number of lane-changing maneuvers by 11% in the daytime, a phenomenon likely to increase crashes in the corridor.