Electric vehicles (EVs)

serving as a novel flexibility resource on the load side

offer substantial schedulable capacity and flexible charging/discharging characteristics. They are transitioning from unidirectional rigid loads to bidirectional flexible resources. To enhance bidirectional interactivity in distribution-transportation coupled systems

this paper proposes an aggregated spatial-temporal flexibility of EVs with dynamic traffic flows. A dynamic traffic assignment model incorporating Vehicle-to-Grid (V2G) interactions is established

considering user equilibrium principles and precise dynamic traffic flow modeling

while integrating EV V2G behaviors and price incentives through charging/discharging coupons. For the distribution network

a second-order cone programming model is established for optimal power flow. Bidirectional charging stations couple the two networks

facilitating the exploitation of large-scale EVs’ potential for grid flexibility support—the visualization of the EV flexible operation region. Case studies of a 33-node distribution network and a 13-node transportation network demonstrate the flexible regulation capability of EVs under varying subsidy levels. Validation against optimal economic dispatch points confirms the feasibility of the flexibility region

while comparisons with static traffic assignment models verify the superiority of the proposed dynamic approach.