Abstract
The road network maintaining stability is critical for guaranteeing urban traffic function. Therefore, the vulnerable links need to be identified accurately. Previous vulnerability research under static condition compared the operating states of the old equilibrium before the event and the new equilibrium after the event to assess vulnerability ignoring the dynamic variation process. Does road network vulnerability change over time? This paper combines the vulnerability assessment with the traffic flow evolution process, exploring the road network vulnerability evaluation from the perspective of time dimension. More accurate identification and evaluation of vulnerable nodes and links can help to strengthen the ability of road network resisting disturbances. A modified dynamic traffic assignment (DTA) model is established for dynamic path selection (reselect the shortest path at the end of each link) based on the dynamic user optimal (DUO) principle. A modified cell transmission model is established to simulate the traffic flow evolution processes. The cumulative and time-varying index of vulnerability assessment is established from the viewpoint of traveler’s time loss. Then the road network vulnerability assessment combined the traffic flow model with the vulnerability index. The road network vulnerability assessment of Bao’an Central District of Shenzhen, China, reveals that road network vulnerability does contain a dynamic process, and vulnerable links in each phase can be exactly identified by the model. Results showed that the road network would have a large vulnerability during the disordered phase when the main road fails. Therefore, prioritizing the smooth flow of main roads can weaken the impact of road network vulnerability exposure.
Highlights
Road traffic network is the material basis for the existence and effectiveness of traffic activities
After the time of T, since the incident occurs at time ka, the road Bottom Vertex (BV) detects that the vehicle outflow is zero, or the road Top Vertex (TV) meets that the number of vehicles in the cell (n) equals the number of vehicles that the cell can accommodate (N)
After reaching the top node of the incident link, the shortest path is selected again based on taking this node as a new starting point, and the destination transmission is continued according to the normal transmission mode. e upstream cell vehicle U-turn driving method can be specified as ni−1(k + 1) ni−1(k) + yi(k) − yi−1(k), (22)
Summary
Road traffic network is the material basis for the existence and effectiveness of traffic activities. The conventional DTA model cannot accurately reflect the changes of various traffic operating parameters in the road network under the influence of the event Factors such as vehicle retention, queue length limitation, and maximum traffic capacity of the road section need to be considered. Travel route selection needs to follow certain traffic distribution rules, as the first-principle requirement of Wardrop equilibrium: all the paths adopted must have the shortest travel time, and the travel time is equal In this model, it can be expressed as follows: if there is a new vehicle inflow in a road link, the road segment must be included in one of the shortest paths; otherwise, the optimal path selection condition for vehicle inflow will not be added.
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