分析了高速公路立交入口区域车辆行车特征,提出了碰撞危险指数概念,考虑了碰撞可能性系数、碰撞车辆速度差、目标车道跟驰车辆在碰撞时的速度、加速度、前后车辆间距5个因素,将入口区域车辆可能发生的碰撞行为分为5种情形,研究了5种情形的发生条件,建立了相应的风险评价模型。针对不同的主线车辆运行车速、车头间距和匝道驶入车辆运行车速进行了三维数值模拟,得到了入口区域行车风险的变化规律。分析结果表明:主线运行车速越大,前后车辆间距越小,车速差越大,其行车风险也越大。 This paper analyzes the driving characteristics of vehicles in the entrance area of ​​expressway interchange and puts forward the concept of collision risk index. Considering the five factors of collision possibility coefficient, collision vehicle speed difference, speed, acceleration and distance between front and rear vehicles in collision of target lane following vehicle, The possible collision behavior of vehicles in the entrance area is divided into five kinds of situations, the conditions of occurrence of five kinds of situations are studied, and the corresponding risk evaluation model is established. Three-dimensional numerical simulation was carried out for different mainline vehicle running speed, headway distance and ramp-in vehicle running speed, and the change rule of driving risk in entrance area was obtained. The analysis results show that the bigger the running speed of the main line is, the smaller the distance between the front and the rear of the vehicle is, and the larger the difference of the vehicle speed is, the greater the driving risk is.