The imbalance of supply and demand in urban transportation has been attracted significant interests. Directional lanes have been widely implemented in Chongqing, China to mitigate congestion and improve efficiency. Directional lanes are usually designed as concurrent with general purpose lanes, and separated by a barrier or painted stripe with an at-grade ingresses and egresses. However, the kind of design may result in weaving segments between egress and off-ramp. The primary objective of the study was to determine the minimum weaving length to meet the demand between the ending point of directional lane and the diversion point of urban arterial road. Based on the driver's most unfavorable driving conditions, the minimum clear distance is defined to explore the components of the clearance. Then, based on the actual investigation, this study analyzes the layout of the directional lanes, the vehicle's type of lane change and the effect of the number of lane changes on the clearance. The minimum clearance calculation model is established from the aspects of sign recognition, judgment and decision, lane-changing and safety confirmation based on the driver's driving characteristics. The recommended value of minimum clearance was proposed, and the rationality and feasibility of the value is verified by VISSIM simulation software. The key results showed that road safety level is safe when the minimum clearance is greater than or equal to the recommended value. Moreover, the increase of the arterial design speed and the increase of number of arterial lanes will increase the minimum clearance from the ending point of directional lane to the diversion point of urban arterial road.

CICTP