Modeling on-ramp capacity with driver behavior variation

Considering the variation of drivers' merging behaviors on the on-ramp of urban expressway, a gap acceptance theory model with variable critical gaps is proposed to measure the on-ramp capacity. When drivers travel along the acceleration lane of an on-ramp, the closer the driver is to the end of the acceleration lane, the stronger the driver intention of merging into the main road would be, and a smaller critical gap will be selected. Consequently, the drivers critical gap of merging decreases along with the acceleration lane of an on-ramp, which leads to the theoretical capacity of on-ramp at different position in the acceleration lane changed as well. Finally, a numerical example is given to illustrate the difference in capacity between the variable and fixed critical gap condition. The results indicate that the on-ramp capacity of the proposed model is always larger than those of the conventional model with fixed critical gap. Moreover, the above-mentioned difference is more obvious under oversaturation conditions.