关键词: 高架道路出口匝道, 工程措施边界条件, VISSIM仿真, 排队长度, 疏散能力

Abstract: Currently，some exit ramps of elevated roads in Shanghai are so crowd at peak time that they face to be taken of engineering measures. Boundary conditions of engineering implementation at zone of exit ramp of road are studied by using VISSIM software to model. Firstly，the evacuation capability of the exit (the largest traffic volume to leave the ramp and to get through the intersection ahead) is determined on the condition that the queue length of vehicle at the zone of exit ramp does not go back to the main line，which establishes theoretical foundation for the control and organization of exit ramp. Then，with the combination of existing traffic demand，the sufficient conditions and necessary conditions of engineering implementation are determined quantitatively，which can provide a theoretical basis for the engineering implementation at zone of exit ramp of elevated roads in Shanghai or other cities in China.

Key words: exit ramp of elevated road, boundary conditions of engineering implementation, VISSIM simulation, queue length, evacuation capability