Sub-problem 2c: What is the level of service at the ramp junction at the northbound on-ramp to I-87?

Let's now consider the questions from the previous page and Exhibit 4-31.

What is the significance of the parameter, P_FM? One of the most important functions of the merge point analysis is to estimate the lane distribution of traffic in the vicinity of the merge point. The proportion of the approaching freeway flow remaining in lanes 1 and 2 immediately upstream of the merge point is noted as P_FM. This parameter depends on both the number of lanes on the freeway mainline and the length of the acceleration lane from the ramp to the mainline.

For this particular analysis, the value of P_FM is 0.59. This means that 59 percent of the approaching freeway flow remains in lanes 1 and 2 immediately upstream of the merge point. If the freeway had more lanes at this point, this value would be lower, as more of the mainline traffic would avoid the turbulence of the merge area.

Which data from Exhibit 4-31 describe the nature of the flow of traffic in the merge influence area? Several model outputs help us to understand the nature of the flow in the merge area. The flow rate in the merge influence area (v_R12) is compared to the capacity of the area to determine whether this area is under capacity or over capacity. The density and speed of the merge area is also computed; the density is used to determine level of service.