Setting minimum vehicle speed limit on freeway based on speed scattering and economic speed

In order to provide a theoretical basis for drawing up a reasonable vehicle minimum speed limit(MSL)on freeway standard to ensure its traffic safety and energy saving,the method to set the MSL was studied based on the vehicle speed scattering constraint and considering the vehicle minimum fuel consumption as the target.The concept of the vehicle speed scattering was proposed and its calculation method was given.The model of relationship between the speed scattering and the traffic accident rate was built using the regression analysis method(RAM),and the threshold value of the speed scattering was defined.The constraint condition for the MSL was given from the need of traffic safety,i.e.the MSL should be higher than 62% of the maximum speed limit.Taking the minimum fuel consumption as the target function of setting MSL,the model of relationship between the fuel consumption and the vehicle speed was built using the RAM,the economic speeds under different grades were given.The MSL should be the higher value from the 62% of the maximum speed limit and the economic speed,which on the one hand ensures the vehicle speed distribution as uniform as possible,reducing the probability of road traffic accident,on the other hand is in favor of decreasing the vehicle fuel consumption,providing a support for energy saving of freeway operation from the management side.