The bridge is the key node of expressway operation. The special structural characteristics of the bridge deck and pavement connection lead to the existence of a critical point of icing, so there is a greater operational risk. In order to study the safety state of vehicle operation under the critical conditions of the road bridge connection, it is of great significance to improve the level of expressway traffic safety. Aiming at the problem of expressway operation risk behavior under the critical state of bridge icing and subgrade section not icing, this paper studied the friction coefficient of dry pavement, light snow pavement and thin ice pavement under the critical state based on the meteorological environment simulation experiment system. Based on the friction coefficient of different road conditions and combined with the driving simulation experiment system, the driving behavior data of average speed, longitudinal acceleration, lateral acceleration and steering wheel angle are collected. The results show that the characteristics of driving behavior change at the road bridge junction in three different critical states are significantly different. The driving risk value under the road surface state in the road bridge junction 3 is calculated by the efficiency coefficient method, It is concluded that the critical state at the road bridge junction has a higher risk level.