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This paper explores the network properties when queues spill over network links, by examining a paradox of network expansion. In networks, each commuter simultaneously chooses departure time and travel route to minimize the travel cost including journey time and unpunctuality penalty. Using some necessary conditions of dynamic user equilibrium, the dynamic network flows are exactly obtained on some small networks. Then we use a network with two origins and two destinations to illustrate an interesting paradox that is caused by the FIFO behavior among commuters traveling on a common upstream link of which the exit is blocked by one branch of downstream traffic. The comparison analysis in this example shows that point-queue models often overestimate the network performance and consideration of queuing spatial dimension in dynamic traffic assignment is necessary |
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Keywords:Braess’s paradox, simultaneous departure time and route (SDR) choices, dynamic traffic assignment (DTA), bottleneck, queue spillover |
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