Acceleration Length Model of an Eight-Lane Freeway with a Two-Lane Ramp Based on Driving Behavior

The current guidelines in China are mainly based on four-lane freeway, which do not fit eight-lane freeway well. Therefore, this paper researched traffic stream characteristics of the on-ramp region of Zhengyi interchange. As a result, the acceleration lane is divided into three regions—the region marked with entrance markings, the region where lane 1 connected with the inside lane of the ramp and the region where lane 1 connected with the outside lane, among which, the minimum length of merging length is calculated as a non-linear integer programming (NLIP) based on the gap acceptance theory and traffic volume. The trial results of the models above show that the present recommended value of acceleration lane length and cannot meet the vehicles’ merging demand under secondary serve level when the freeway is eight-lane with two-lane ramp.