Passenger car equivalents of trucks under lane restriction and differential speed limit policies on four lane freeways

Truck lane restriction and differential speed limits for trucks and cars are becoming more common policies to improve freeway operation and safety. It is hypothesized that passenger car equivalents for trucks are impacted by freeway operation under such restrictive conditions, which are not explicitly addressed by the current edition of the highway capacity manual. In this study, passenger car equivalents for trucks were estimated from simulated and real-world data collected from an elevated 18-mile four-lane rural freeway section in Louisiana with no significant grades. It was found that passenger car equivalents for trucks depend on the flow rate, traffic mix characteristics and compliance level to truck lane restriction. Near capacity conditions, the estimated passenger car equivalent for trucks fell in the range of 2.0 to 3.0. These values are significantly higher than the suggested highway capacity manual value of 1.5. Linear regression models were developed to estimate the relationships between passenger car equivalents for trucks and the percentage of trucks and the level of compliance to truck lane restriction.