Safety Analysis And Optimization Desion Of Urban River-crossing Tunnels Based On Simulation

As an important part of urban road traffic system,the safety of river-crossing tunnels is of great significance.Based on the geometric parameters,lane width,speed and average daily traffic flow information etc.of Shanghai 12 river-crossing tunnels,12 simulation models were established by VISSIM.Then an exponential model between speed standard deviation and accident rate was set up by calculating speed standard deviation of 12 tunnels.Via inputting the vehicle trajectory files into SSAM,traffic conflict data was adopted.Afterwards a power function relation between traffic conflict rate and accident rate was delivered.Parameters of gratitude,speed limit,heavy vehicle ratio and traffic flow characteristics were varied to set different simulation scenarios in VISSIM.Speed standard deviation and traffic conflict rate under different scenarios were analyzed.Several advices were given according to predicted accident rate,which could be applied in the design and operation stage.Moreover,a binary logistic regression model was established to predict accident severity of urban river-crossing tunnels.Ten candidate independent variables were selected from the aspects of time,road structure and traffic environment.Then by the method of reverse stepwise selection,seven variables,such as day of week,peak hours or not,daytime or nighttime,gratitude,vehicle types involved,speed limit,traffic volume,were identified contributing to the accident severity in urban river-crossing tunnels.Finally,in consideration of accidents rate and accident severity,suggests for the design and operation of urban river-crossing tunnels were proposed.