Research On Speed Limit Value Of Ramp Passenger Cars On The Exit Of Interchange Of Mountain Expressway

To ensure the traffic safety and improve the operational efficiency,reasonable speed limit is an indispensable measure.However,at present,for the ramp section of the mountainous highway interchange,the selection of speed limit values of the diverging gore nose is generally determined by the form of the ramp and the design speed of the main line of the highway.Due to the geological constraints of mountain areas,to a certain extent,the selection of the upper limit speed value is too conservative.After the field survey,at the diverging gore nose of the ramp exit of the mountain expressway interchange,the actual operating speed of most car drivers is often faster than the ramp speed limit value;By related questionnaire surveys,many car drivers also believe that the speed limit value of the ramp exit on the interchange with a better linear shape does not meet their psychologically expected speed,and consider that the speed limit value is set too low.Therefore,in order to determine the exit ramp speed limit value of the high-speed interchange rationally and at the same time to ensure the driving safety of these passenger drivers,it is necessary to conduct a relevant study on the exit ramp speed limit value of the interchange based on the running speed.The article takes the car under free flow as the research object,focusing on characteristics of cars driving at the deceleration lane of theexit ramp,transition curve at the exit of the interchange and ramp curve control section,discusses the relationship between the limited speed and operating speed,design speed,average speed and establishes the corresponding theoretical model,which provides a certain basis for the establishment of ramp speed limit value and some references for the ramp design and traffic management.To analyze and research the operating speed characteristic of the car in the deceleration section of the exit ramp.Driving data of the car were recorded in real time via using a small drone to take aerial photographs of the expressway deceleration lane section of the interchange(from the transition section to the diverging gore nose of the ramp).By the normality test of the car driving speed,the calculation of the operating speed of the characteristic point,the regression coefficient analysis and the test of the independent variable parameter relationship,the prediction model of the car operating speed on the ramp of the expressway interchange was established,and the correlation between the predicted operating speed of the car at the diverging gore nose and the speed limit value was studied.What' more,comprehensively considering factors such as the sight distance at the ramp exit and the design speed,and meeting the requirements of the current standard deceleration lane length,the speed limit value is finally determined.To study the operating characteristics of the car in the circular curvespeed-change section of the exit ramp.In this part,practical experiments are used as the means to obtain research data.14 car drivers with driving experience are randomly selected.Physiological instruments are applied for the collection of the driver's heart rate data during the ramp driving.The GPS is used to collect the driving speed of the car.Based on the measured data and the statistical analysis,the test data and ramp profile parameters are analyzed and studied,and the relevant regression analysis model is established.The heart rate growth rate and average speed were used as indicators to characterize the driver 's physiological response and vehicle operating characteristics,respectively.Based on these indicators,the quantitative relationship between them and the ramp linear parameter index are established.Moreover,the correlation between the driver's heart rate growth rate and average speed,ramp speed limit value is discussed.Finally,the satisfying ramp speed limit value were gained with meeting the requirements of the existing standard ramp control curve radius and slope.