Assessing The Benefits Of The Auxiliary Road Metering System

Auxiliary road metering is the use of traffic signals at the auxiliary road of expressway near the exit to control the rate of vehicles through the exit area which aims to ensure the vehicles travel from the mainline to the auxiliary road smoothly. This system has been deployed in Beijing expressway for a few times. With the passage of time, people become more and more concerned about the effectiveness about this system. There are many questions needed to answer, such as what can it bring to us and is it a useful tool to solve the traffic congestion.This paper established a framework and measures of effectiveness used for assessing the benefits of Auxiliary road metering system, and the applicable evaluation method also was chosen. After these works, a case study was performed to assess the actual system deployed in the southern exit of Dongsi-shitiao Bridge of inner second ring road. From this research, we can draw some conclusion: (1) In some special time, the system can effectively improve the efficiency and throughout, especially when the traffic demand is high. (2)The auxiliary road user are the loser, they encounter some unavoidable delays. The system can also generate a long queue which may affect other neighboring network and the entrance when the auxiliary road volume is high. (3) Not all the vehicles which travel from the mainline to auxiliary road are the winner. Some may benefit from the system, others are not. (4) The control strategy needs to be improved. The simulation test result shows that the long cycle fixed time control strategy which has long time red cycle and green cycle may worsen the traffic condition under some special traffic demand. (5) Not all system that has been deployed operate effectively, it means that it should make some investigation which include the reason that make the exit congestion, traffic demand and surrounding environment before the system deployed.