Evaluating Designs of a Three-Lane Exit Ramp Based on the Entropy Method

The interchange diverging area is a bottleneck section of the freeway. If the capacity of a two-lane exit cannot meet the traffic demand, it will lead to a reduction in the overall operational efficiency of the freeway. To fundamentally improve the capacity of the diverging area, designers have considered expanding the two-lane exit to a three-lane exit. However, the existing Chinese design specifications do not include a design for a three-lane exit, and the method of increasing the number of ramp lanes by setting up auxiliary lanes according to traditional design concepts leads to the mainline widening section being too long, thus increasing the construction land use and project cost. Therefore, this paper proposes an innovative three-lane exit design based on a specific two-lane exit at an interchange in Xi'an. According to the different traffic organization methods, three microscopic simulation models of diverging areas were constructed by using VISSIM. The entropy method was used to objectively calculate the weights of the four selected evaluation indexes, and a comprehensive evaluation and applicability analysis of the current situation and the three-lane exit design schemes were conducted. The results show that the optimal combination of the schemes calculated by the entropy method increases the traffic volume by up to 40% and reduces delays by 50-88%.