Research On The Standards And The Methods For Freeway Speed Limitation

With the rapid social and economic development in China, the freeways in China are playing a more and more important role in the transportation system. The passengers and freights transportation by highways are constantly rising in recent years. Speed-limits have been widely used as way to balance between the safety and operational efficiency of freeways all over the world. At present, the main problem of speed-limits on freeways is how to set the standards, the methods and the related facilities for speed-limits on freeways and the research on this field has not been adequately done. Based on the analysis of freeways in China and the research on speed-limits for freeways at home and abroad, the state of the art in speed-limit on freeways in China and over the world the outcomes of this research are concluded as follows:(1) Based on the studies and analysis of the relationships among the design speed, the expected speed, the operating speed and the speed-limit, the concept of setting speed-limits in terms of the traffic survey and the actual operating speed of vehicles is proposed in this thesis. It is unscientific and unreasonable to use the design speed as the standard of the actual speed-limit for freeways. The operating speed plays the most important role in the research of speed-limits for freeways. The design speed and the expected speed must be also regarded as the valuable references in the research.(2) According to the influencing factors of speed-limit standards, the content of traffic survey must includes the data of traffic volume and the operating speeds on freeways, the alignment of freeways, the records of traffic accidents and so on. In addition, the attentions during the traffic survey are also discussed in this thesis.(3) Based on the impact of the relationship studies between the operating speed and the traffic accidents, this thesis points out that over speeding is one of the most important reasons causing traffic accidents. The higher discrepancy of operating speeds would lead to a higher rate of traffic accidents, and the absolute higher operating speed would lead to a more serious accident.(4) The standards and the methods of freeway speed-limits are studied in detail, and the method to determine the maximum and the minimum speed-limit standards are proposed in this research. It is recommended that multi speed-limits management method has higher feasibility and better effect, such as speed-limits with speed zones and speed-limit considering the different lanes and the vehicle types, etc.(5) The facilities related to speed-limit enforcement have an enormous effect on freeway speed control, and the most common speed-limit facilities include the speed limit signs, the speed limit markings, the camera monitoring equipments, the radar devices, the speed control equipments in vehicles, and so on. In this thesis, the installation, the operating environment and the effects of those facilities mounted and operated on freeways are studied and analyzed in detail.Finally, through a project study, this thesis has proposed the standards and methods for setting freeway speed-limits based on the traffic investigation, the analysis and the research for the project.