Abstract: Through the investigation of vehicle speed，vehicle composition，road alignment，altitude oxygen content and current speed limit combination mode of two-lane highway in Qinghai Tibet plateau，the car speed limit velocity mean model and speed mean-operation speed model of two-lane highway in plateau area were established respectively by the method of multiple linear regression and SPSS statistical software，considering the control delay caused by the speed limit as an index to evaluate the operation efficiency of the plateau highway. Finally，the interaction model between speed limit and operation efficiency-delay was obtained. The results show that ：the speed limit value of the car and cart，the longitudinal slope of the road，the length of the road section and the design speed of the road have an influence on the running efficiency of the vehicle running on the road system. The difference is that the factors such as different road grade and the proportion of cars on the road will have a certain impact on the efficiency of the car，but a little impact on the cart. In addition，with the increase of altitude，the operation efficiency of large and small cars is gradually decreased，and the delay caused by the cart is higher than that of the car.

Key words: traffic engineering, Qinghai-Tibet plateau, two-lane highway, limit speed, operation efficiency, delay, traffic safety

摘要： 通过对青藏高原双车道公路车辆运行速度、车辆组成、道路线形、海拔氧含量以及现状限速组合方式的调查，考虑将限速导致的控制延误作为衡量 高原公路运行效率的指标，应用SPSS统计学分析软件，采用多元线性回归的方法，分别建立了高原地区双车道公路大、小车限制速度—速度均值模型和速 度均值—运行速度模型，最终得到了限制速度对运行效率-延误互动关系模型。结果表明：大小车的限速值、道路纵坡坡度、路段长度和道路的设计速度 都对道路系统行驶车辆的运行效率产生影响，而不同的是不同的道路等级、道路上小车所占车辆的比例这些因素会对小车的运行效率产生一定的影响，而 对大车的影响不大，另外随着海拔的增加，大、小车的运行效率逐渐降低，且大车所产生的延误比小车要高。

关键词: 交通工程, 青藏高原, 双车道公路, 限速, 运行效率, 延误, 交通安全