Jacobs Journal of Civil Engineering

Traffic Capacity of Interchange Circular Loops

Published on: 2019-03-05


The major objective of this research was to determine the capacity of circular loops at suburban interchanges. To achieve this objective, ten interchange loops with different radii were selected. Data on traffic operation variables at loop entrance, loop exit, and middle part of the loop (proper) were obtained using video camera. Also, data on loop geometric were obtained through field survey. Results of analysis indicated that loop proper capacity under Jordanian conditions is significantly lower than those presented in the Highway Capacity Manual. Two loop proper capacity models were developed using loop radius or free-flow speed as determinate variable. The analysis also revealed that loop exit capacity is influenced by the traffic flow on the outer arterial lane. Using regression analysis, an exponential model was developed to estimate loop exit capacity. Furthermore, a linear model was recommended to estimate loop entrance capacity, using loop radius as determinate variable. Finally, results of the study showed that loop entrance and exit capacity values in Jordan are comparable with those presented in the literature, and the exit capacity is the critical value that determines the capacity of the loop ramp.


Interchange; loop capacity; circular loop; exit; entrance; proper; regression