Study On The Design Method Of Interchange Alignment Based On Operating Speed

At present, the design method of highway and interchange alignment is based on design speed in China, the designers just control the minimum standards of parameters according to the requirements of the specification when designing, resulting in the apparent inconsistencies between the speed when driving on the highway and interchange and the designing speed,it is likely to cause traffic accidents. Therefore, this article proposes to the method of using operating speed to design the alignment of interchange’s mainline and ramps.Firstly, this article analyzes the characteristics when vehicles travel on the interchanges’ ramps, and the traveling process on the interchange is separated into three sections: deceleration section, uniform section and acceleration section, and analyzes the relationship of the vehicles’ operating speed in this sections with their influencing factors, establishing the theoretical basis for the models. Then according to China’s traffic conditions, formulates appropriate survey method, and investigates the vehicles’ traveling speed of the feature points of four interchanges in Xi’an, and gets the corresponding data through the field investigation, establishing digital basis for the models.Drawing the operating speed’s trending chart of the interchanges’ mainlines and the ramps basing the investigative data, and analyzing the correlation between the operating speed of each sections and corresponding factors, then using the mathematical and statistical software SAS to regress and analyze the operating speed models in the mainlines and the ramps’ corresponding sections of the representative vehicle types and analyzing the significant tests to verify the fitting degree and the reasonableness of the regression models.Finally, introducing the speed coordination evaluation criteria and the corresponding evaluating steps of the interchanges’ mainlines and ramps by using the operating speed, and combining with engineering examples and using the established operating speed models of interchanges’ mainlines and ramps to analyze the application situation of the models.