Abstract: Limited by the topography, planimetric features and other conditions, it is common that the portal sections of tunnels are located on swing curves. For the safety of the driving, in relevant specifications there are special requirements on the planimetric alignment consistency of the portal sections of tunnels. However, it is difficult to fulfill these requirements. In this paper, a quantitative criteria to check the planimetric alignment consistency of the portal sections of tunnels is proposed on basis of the critical inside movement value "p", which is calculated according to the minimum radius of the circular curve without the transition curve and the minimum length of the swing curve specified in Design Specification for Highway Alignment (JTG D20—2006). The quantitative criteria proposed is as follows: the deviation between the end point of 3s driving at the design speed from the tunnel portal and the position reached by the driver following 3s driving at the design speed should be less than the critical inside movement value "p", otherwise, it is considered that the consistency requirements have not been met.

Key words: highway tunnel, portal section, 3s distance, planimetric alignment consistency, verification