以上海市罗山路工程为依托，在施工阶段逐层进行了测定，包括回弹弯沉、承载板测定路面当量回弹模量、各结构层底面应变状态等。通过测定数据的分析，研究半刚性基层沥青路面各结构层的贡献情况，对分析半刚性基层沥青路面结构的结构性能，进行路面结构的组合设计具有较大的参考价值。

通过室内试验，研究了2种用于高等级公路半刚性基层材料（水泥碎石、二灰碎石）的回弹模量、强度指标、干缩和温缩特性。试验结果表明，半刚性基层材料抗压模量和弯拉模量存在差异，动态模量远远大于静态模量。材料的抗压强度、劈裂强度和弯拉强度等指标随试验方法的不同而存在显著差别，因此，应根据半刚性基层的受力状态选用对应的材料强度和模量指标。

The generally road safety situation of highway net was evaluated through investigating road safety of some highways and analyzing accident patterns and causes. Some sections with high accident rate were found using road black spot identification technology. Then, accident causes related to highway features and traffic factors were analyzed. The characteristics of typical black spots were analyzed from the aspect of highway features and traffic devices. Running speed of vehicles on highways was measured in order to explain why over-speed driving always was primary accident cause.

In terms of traffic accident statistics in recent years sampled from a typical heavy transportation freeway in China and based on the field survey of vehicle operating speed on highway sections, the influence of heavy vehicles on freeway safety with regard to vehicle running theory, freeway environment and drivers' characteristic, and so on was studied. The research result shows that the main causes of accidents are related to driving performances, such as over-loading and significant speed variation among various types of vehicles. In view of this, the paper puts forward the corresponding measures for safety improvement from aspects of engineering and traffic management.

Speed management is essential for ensuring the operating safety of highclassified highway. This paper discusses the setting, dissemination and implementation of speed limits based on the current state of speed management in China, and points out the concept of dynamic speed limits and the method of setting the dynamic speed limits according to highways characteristics, traffic volume, weather condition and accidents history. Finally, the paper puts an emphasis on the importance of traffic safety culture to the implementation of speed limits.