Impacts of heavy vehicles on inter-vehicle interactions and passenger car equivalents for tunnel traffic

Although traffic parameters for tunnel sections may vary significantly as compared to an open freeway section due to difference in geometric conditions and driving condition, very limited number of research has been done to understand traffic operations on tunnels. This paper aims to fill this gap by evaluating the Passenger Car Equivalent (PCE) factors for heavy vehicles (HV) based on individual vehicle observations from a study section containing the Hampton Roads Bridge Tunnel (HRBT) in Hampton Roads, VA. In addition, the impacts of bottleneck location on the PCE factors under different HV percentages in the traffic stream is also examined in the paper. The analysis revealed new insights into the inter-vehicle interactions for tunnels. It is found that the level of HVs in the traffic stream has a significant influence on passenger car (PC) as well as HV headways. Also, the estimated PCE values for the tunnel section were found to be different than the Highway Capacity Manual (HCM) 2010 suggested PCE values. The location of bottleneck was found to impact the PCE values.