The energy-equation for steady rapidly varied flow is given herein; with which some problems from the rapidly varied flow can be effectively solved, and then a specific formula is also put forward on the basis of the concept of “additional pressure from bendings” In this way, the streamwise variations of the hydraulic factors such as the water depth, velocity etc.

The rational length of auxiliary lane and channelization of urban expressway exit have an important role to increase the exit capacity and decrease the influence to expressway traffic flow from exit.