Driving risk evaluation and speed control in passageway areas of freeway

The traffic flow characteristics and accident reasons in the passageway areas of freeway were analyzed.Based on vehicle critical deceleration and unsafe degree, risk level was changed from two dimensional vector to one dimensional scalar.Braking decelerations and unsafe density indexes were put forward as the driving risk evaluation indexes of passageway areas, and a driving risk evaluation model was established.According to safety risk management regulations and human-mechanism engineering theory, risk grades and evaluation standards were dertermined.On the basis of many experiment data, the suggested values of main line driving control standards in passageway areas of freeway were proposed.Analysis result shows that when speed is not limited, the driving risk of outlet area is middle.When speed is limited at 65 km·h^-1, the driving risk of outlet area is low, and the average risk value is smallest.The peak value of unsafe density index reduces from 0.112 to 0.064, and decreases about 42.86%.When speeds are limited at 55, 50 km·h^-1, the risk of outlet area is high, and the peak values of unsafe density indexes rise to 0.125 and 0.121 respectively.Obviously, the limit measure of 65 km·h^-1 is most effective.