I-15/Limonite Ave Interchange
Improvement Project
This interchange type is a standard tight diamond with Continuous Flow Intersections instead of standard signal controlled intersections. Instead of having left-turn movements occur at the intersection they are instead displaced into dedicated lanes on the opposite side of the road. When these lanes hit the intersection they are able to make free-left turns. In order for this to function an extra signal is added on the approach to the intersection where the left-turn vehicles are able to get across the road.
A Synchro Analysis was conducted on the Continues Flow Interchange to determine whether or not it was capable of handling the predicted 2040 traffic volumes. Initially the analysis determined whether or not the interchange would produce an improvement in the level of service. After it was determined that it did the program was used to determine the lane configuration that would produce a desirable level of service. This produced a lane configuration that gave a level of service of C for both intersections.
This was possible because the Continuous Flow Interchange displaces the left-turns that otherwise would have impeded through movement across the bridge. This allowed the signals to function wih just 2 phases. However, it is worth noting that although the additional intersections also had an acceptable level of service the overall delays they add to the interchange was not determined. This alternative is still considered viable at this point and will move on to the next step in the selection process.
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Result: Passed
The possible negative impacts of the Continuous Flow Interchange to the surrounding area were evaluated in this step. The design does go through the nearby park and ride facility, which will need to be relocated. This is further discussed in the Park and Ride Design tab under Deliverables.The layout also has a negative effect on the driveways located near the displaced left turns. These new left turn movements create a new and confusing situation for drivers trying to enter and leave the adjacent driveways. With this in mind, we determined some of the driveways would need to be closed to maintain driver comfort and expectation. However this would have unacceptable consequences for the businesses near those driveways. This removes the continuous flow interchange as a viable alternative.
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Result: Failed
C
C
Continuous Flow Interchange
Traffic Analysis
Viability
The continuous flow interchange interchange passed the traffic analysis and geometric feasibility steps but failed with impact evaluation. Therefore it is not considered viable and was rejected at that step.
Geometric Feasibility
This step involved making a rough design for the Continuous Flow Interchange. We determined that the interchange could be laid out within the existing right of way and undeveloped land, while still providing the capacity determined in the synchro analysis. This alternative is still considered viable at this point and will move on to the next step in the selection process.
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Result: Passed