Jordan Journal of Civil Engineering

Consistency and Performance of Interchange Loops


Hashem R. Al- Masaeid; Mohammed Taleb Obaidat; Ahmad S. Hjouj;


The objective of this study was to investigate drivers’ behavior, including traffic speed and vehicle lateral placement, as well as accidents at interchange loops. Twenty seven loops located in rural and suburban areas were investigated. For different vehicle classes, loops were evaluated using four measures; speed profile, speed consistency, vehicle lateral placement and traffic accidents. Data on loop characteristics, traffic speed and lateral placement of vehicles was obtained through field measurements. Analysis results revealed that entrance, exit and the middle part of the loop are critical locations. Loop entrance and exit exhibited speed inconsistency and experienced a large number of collision accidents. The use of circular curve with a radius of more than 70 m may eliminate this problem. At the middle part of the loop, vehicles were found to get closer to the inner edge of the pavement and this location experienced considerable loss-of-control accidents. Results also indicated that passenger car is the critical vehicle for a consistent design.


Interchange loops, Speed profile, Consistent design, Lateral placement, Accidents.