Abstract: Taking the left turn vehicles at signalized intersection as research object，this paper presents two kinds of traveling trace simulation model for left turn vehicles based on numerical approximation and geometry principle.For current traffic state，cubic parabolic model is built by using best approximation in the mean and Chebyshev approximation，and tested by an example.For the future situation after stop line changed，the line-clothoid-clothoid-line model is presented.Further more，this paper also deduces a linear model about the relationship of stop line position and critical radius，calculating parameter of clothoid easier.The simulation program indicates that models built approximate the real traffic situation better.

Key words: simulation modeling, traveling trace simulation model for left turn vehicle, numerical approximation, clothoid

摘要： 以信号交叉口左转车辆为研究对象，根据数值逼近和几何学原理，建立了停车线位置改变前后两种不同的左转车辆行驶轨迹仿真模型。对于当前交通状态，采用最佳平方逼近和Chebyshev近似原理的方法，建立了左转车辆行驶轨迹的三次抛物线模型，并通过实例予以验证；对于停车线位置改变后的未来状态，给出了直线—回旋线—回旋线—直线组合的左转车辆行驶轨迹模型。进一步，建立了停车线位置与临界半径函数关系线性模型，使回旋线参数计算更为简单。仿真结果表明，所建模型较好地逼近了相应交通状态。

关键词: 仿真建模, 左转车辆行驶轨迹仿真模型, 数值逼近, 回旋线