Finite Mixture Distribution Method to Model Vehicle Headways at Port Collector-Distributor Roads

This study aims to model vehicle headways comprising non-free flow headways (i.e., headways under non-free flow traffic conditions) and free flow headways (i.e., headways under free flow traffic conditions) on port collector-distributor roads using the finite mixture distribution method with two mixture components. Three combinations of leader-follower vehicles were found to be statistically different. Six factors, consisting of truck percentage, traffic flow rate, weather, curbside parking, light condition, and road pavement condition were considered as influencing factors. Model comparison results indicate that the finite mixture distribution model outperforms the single distribution model. Results show that rainy days, curbside parking, poor light condition, and poor pavement performance are associated with an increased mean headway for car-car, car/truck, and truck-truck types. The headways of these three types are generally higher for the bigger traffic flow rate, while a larger truck percentage can decrease the mean headway for car-truck and truck-truck types.