Abstract: 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.

Key words: urban traffic, on-ramp, capacity, critical gap, driver behavior, urban expressway

摘要： 考虑城市快速路入口匝道加速车道上驾驶员行为变化特征，以间隙接受理论为基础，建立了可变临界间隙条件下的入口匝道通行能力模型. 当驾驶员在加速车道上向前行驶寻找汇入机会时，距离加速车道末端越近，其试图汇入主线的意向越强烈，所选择的临界间隙也会越小. 因此，驾驶员所选择的可接受临界间隙随着其在加速车道上行驶距离的增加而减小，从而会导致在加速车道不同位置的理论通行能力发生变化. 最后，通过数值算例分析可变临界间隙下入口匝道通行能力与固定条件下的差异. 结果表明：在考虑驾驶员汇入行为变化导致临界间隙减小条件下，入口匝道理论通行能力大于以往固定临界间隙条件下的通行能力，并且，在主路流量较大时这种差异更加明显.

关键词: 城市交通, 入口匝道, 通行能力, 临界间隙, 驾驶员行为, 城市快速路