In this article,the processes of vans running into a one-way two-lane road tunnel are simulated numerically using the dynamic mesh technique and RNG k ? ε turbulence model.The transient aerodynamic characteristics around vans are obtained in three cases:a single van,two vans side-by-side and two vans one after another running into the tunnel,respectively.Through a comparison with the results of the wind tunnel experiment,the transient simulation method is verified.The results show that,when a van runs into the tunnel,the aerodynamic drag coefficient increases near the tunnel entrance,and after entering the tunnel,the side force is generated,pointing to the tunnel wall nearer to the van.When two vans run into the tunnel side-by-side,their drag coefficients increase by 50%,and the side force varies sharply with directions changing twice near the tunnel entrance.When two vans run into tunnel one after another,the aerodynamic characteristics around the van in the front is similar to that of a single van,but the aerodynamic forces on the van behind do not have obvious change.Among the three cases,the aerodynamic forces have a sharp change when two vans run side-by-side,so driving side-by-side into a tunnel should be avoided for safety. In this article, the processes of vans running into a one-way two-lane road tunnel are simulated numerically using the dynamic mesh technique and RNG k? Ε turbulence model. Transient airodynamic characteristics around vans are obtained in three cases: a single van , two vans side-by-side and two vans one after another running into the tunnel, respectively. Through a comparison with the results of the wind tunnel experiment, the transient simulation method is verified. results show that, when a van runs into the tunnel, the aerodynamic drag coefficient increases near the tunnel entrance, and after entering the tunnel, the side force is generated, pointing to the tunnel wall nearer to the van. due increase by 50%, and the side force varies sharply with directions changing twice twice the tunnel entrance .When two vans run into tunnel one after another, the aerodynamic characteristics around the van in the front is similar to that of a single van, but the aerodynamic forces on the van behind do not have obvious change. Among the three cases, the aerodynamic forces have a sharp change when two vans run side-by-side, so driving side-by-side into a tunnel should be avoided for safety.