A cellular Automaton (CA) model was introduced to simulate stochastic traffic, an 18 degrees-of-freedoms (DOFs) vehicle model was used to simulate a heavy truck, and a single DOF vehicle model was used to simulate other typed vehicles in traffic. The simulating stochastic traffic can be improved by considering the influence of the nearest neighbor vehicle. The coupled equations of bridge and vehicles in traffic flows were established by combining the equations of the motion of both the bridge and vehicles using the displacement relationship and interaction force relationship. The simulations show that the effect of considering the nearest neighbor vehicles on the maximal vertical displacement of bridge is significant, and the dynamic vibration of the main beam and tower under stochastic traffic flows cannot be neglected.