Minimum spacing of continuous entrance and exit on the collector-distributor road of alfalfa leaf interchange

Abstract

The spacing between the same side of entrance and downstream exit (continuous entrance and exit) of the interchange has not yet specified in the highway route design specification (JTG D20—2017). When the spacing is small, the interweaved traffic flow affects each other, which not only reduces the traffic capacity, but also affects the traffic safety. In this paper, the collector-distributor road is set in the main line of alfalfa leaf interchange. By analyzing the operation characteristics of vehicles in this area, we obtain the calculation model of minimum spacing of continuous entrance and exit, and determine the key parameters such as the weaving type and the vehicle speed of the weaving area according to 'China Highway Capacity Manual'. Then we calculate the length and saturation of weaving area and examine the length and service level of weaving area. Finally we propose the recommended minimum spacing of continuous entrance and exit of alfalfa leaf interchange. We use the VisSim software to build the traffic simulation model of continuous entrance and exit section, take the conflict rate as the safety evaluation index, and evaluate the simulation conflict rate of the recommended minimum spacing under different design speed combinations. The evaluation results show that the safety levels of the recommended minimum spacing of entrance and exit are safe, relatively safe or criticality safe, indicating that the recommended spacing is reasonable. The research results can provide a reference for the design of continuous entrance and exit on the collector-distributor road of alfalfa leaf interchange, and help to improve the revelent specifications and design rules. <fig fig-type="abstract-image" id="F1" orientation="portrait" position="float"><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="1000-2618-2022-39-3-305/FA80BD8A-2C47-438f-B2C4-18EB183AC195-F001.jpg"/></fig>