Novel Approach for Design of Merging and Diverging Length at Toll Plazas: A Case Study

Abstract

Traffic operations at toll plazas are influenced by the merging and diverging behavior of vehicles near the toll plaza in the flare area. Proper guidelines for the design of merging and diverging sections at toll plazas under mixed traffic conditions are not specified by the Indian Highway Capacity Manual, the Indian Road Congress, or the American Association of State Highway and Transportation Officials. Thus, the present study attempts to develop design criteria for diverging and merging lengths. The field data were collected using the performance-box instrument at Ghoti toll plaza located at National Highway No. 60 in India, operating under mixed traffic conditions. The concept of discretization of speed profile is proposed and applied to segregate sections of the zone of influence into ten equal parts each of 50 m length. The statistical test shows that speed has a significant difference between the sections and also in between the different classes of vehicle. Results of the speed-distance plot show that the second-degree polynomial function is the best fit for zone of deceleration and power function for the zone of acceleration. The study revealed that, for 50 km/h approach speed, the minimum diverging and merging distances should be 125.67–308.98 m and 47.93–294.23 m, respectively. The proposed guidelines for merging and diverging length are useful for the design of the flare area and to improve operational efficiency and level of service at toll plazas operating under mixed traffic conditions.