The signalized intersections are considering one of the critical elements in facility work of urban arterial roads. Thus, it is necessary to improve the signalized intersections system not only to increase the ability of flow on the major and minor roads but also to increase the neighboring freeways ability to work with high efficiency.
In the 4-leg signalized intersections, left-turn effect greatly on the capacity, if left-turn movements eliminated by converting it to right and through, so that, the signal can operate with only two phases instead of four phases and capacity will increase. The objective of this study was to evaluate the influence of eliminating left-turn movements (converting it to through and right movements) on the level of service for an intersection of freeway off-ramps with arterial roadway (figure. 1), in order to decrease the congestion on the oversaturated off-ramps, which affect the traffic flow on freeway. Also studying the influence of this elimination and converting on: (1) average system delay, (2) fuel consumption, (3) average travel time, (4) average delay on freeway off-ramps and (5) average queues lengths on freeway. This elimination and converting will be carried out by constructing two roundabouts (nearby to the intersection) on arterial roadway Figures. (5 & 6). Full-movement signalized intersection with two roundabouts were compared before and after elimination left-turn movements through simulation with the use of the Synchro 6 simulation package. The results showed a significant improvement in level of service for the studied intersection. In addition, significant decrease in average delay and average travel time, and minor decrease in fuel consumption. The results also showed a significant decrease in average delay on freeway off-ramps and queues lengths on freeway.