Sub-problem 3b: Ramps

Let’s look at a couple of different geometric variations that could be implemented to improve performance at this location. The first is a set of finite lengths of the acceleration lane at Location J, assuming the geometry of the merge at Location I is unchanged. We need to establish the acceleration lane length needed to obtain LOS A. The second set of analyses will support the idea of an extended acceleration lane for Location I and the merge that occurs at Location J ties into that lane.

For the first set of analyses, we know that changing the acceleration length at Location J should not affect the analyses procedure for the merge at Location I. Therefore the operation of the merge at Location I will remain a LOS C. Initially, we can do the analysis at Location J, using the volume/capacity comparisons for the lanes entering and exiting the influence area. For the purposes of these analyses, we will start with an acceleration lane length of 1,000 feet and increase this value until we reach a LOS A. The analysis results of varied acceleration lane lengths are shown in Exhibit 4-60. It is clear that as the acceleration lane length is increased, the LOS improves. Furthermore, the analyses show that if the acceleration lane length is set at 3,000 feet, a LOS of A results. Since the actual acceleration lane extends much further than 3,000 feet, the merge can be said to be operating at LOS A.

For the second set of analyses, we will extend the length of the acceleration lane for the merge at Location I to 500, 1,500, and 2,500 feet. Note that the merge at Location I occurs approximately 1,500 feet upstream of Location I. To maintain the same freeway lane configuration at J when the acceleration lane at Location I exceeds 1,500 feet, we need to assume that the on-ramp becomes the third lane. That means we will also need to reconfigure the acceleration lane length for the ramp at Location J.