An acceleration lane should have sufficient length to enable a driver entering a highway from a turning roadway in a safe and comfortable manner. Studies of road safety show that many accidents happen due to the shortage of the length. So, it is to confirm the appropriate length is necessary for safety of interchange design and operation. According to active standard of China, the distance is governed by the speed differential between the operating speed on the entrance curve of the ramp and the operating speed of highway. The design specification suggests that the length of single-lane acceleration lane is not less than 200 meters. However, traffic volume on major roadway has high influence on the length. The value (200 meters) is lower because of neglecting the effect of traffic volume. Based on the traditional method on calculating the length of acceleration lane, the paper takes MaJuQiao Interchange as the research target to stress the effect by major roadway traffic volume. After analysis the vehicle operating characteristic on acceleration lane, the condition of vehicle merging from ramp to major roadway resembles the condition of vehicle crossing the non-signal intersection. Then, the paper resorts to the theory of non-signal intersection merge and presents the new formula applied into confirm the length, which considers the delay caused by traffic volume of major roadway during merging into the highway. The length calculated by new formula is longer than recommend by the standard. After investigate and compare, the former can meet the demand better than the latter. For the covering abstract see ITRD E138091. This paper is available from http://www.ictct.org/workshops/07-Beijing/710XuQiushi346349.pdf.
Abstract