The reasonable value of the minimum distance from the exit of an expressway tunnel to the toll station was explored. The driving process from the tunnel exit to the toll station was analyzed, and the calculation formula for the distance under the worst conditions was provided. By introducing reliability theory and establishing the functional function, the relationship between the distance from the tunnel exit to the toll station and the reliability of this distance for different numbers of lanes was analyzed. The recommended value of the distance from the tunnel exit to the toll station under different design speeds was inversely calculated. Finally, the rationality of the reliability design was investigated through VISSIM simulation. The results indicate that the average speed of vehicles on the road section, designed with the recommended reliability value for the minimum distance from the tunnel exit to the toll station, is increased by 8.6% to 11.8%, and the traffic conflict rate is reduced by 19.1% to 22.7%. It was demonstrated that the research findings could enhance the traffic fluency and safety of the road section from the tunnel exit to the toll station, indicating certain practical significance.