Sub-problem 2d: How Can We Improve the Level of Service at the Ramp Junction at the Northbound On-Ramp to I-87?

Exhibit 4-34 shows the results of adding a lane to the freeway mainline, with a direct comparison to the conditions before the lane was added. The most direct result of adding a lane is the increase in the mainline capacity from 6,750 to 9,000 pc/h. This has several related impacts. The proportion of approaching freeway flow remaining in lanes 1 and 2, P_FM, decreases from 0.59 to 0.08, because the traffic remaining on the mainline is more likely to avoid the congestion inherent in the merge area: two lanes are now available for through traffic rather than one in the before case. This also shows in the traffic in the merge influence area (lanes 1 and 2 plus on-ramp), VR₁₂, decreases from 5,265 to 2,526. After the lane is added, this flow rate is below the maximum (capacity) of 4,600.

The overall performance of the merge area increases dramatically from LOS F before to LOS C after the addition of the lane. The speed of vehicles in the ramp influence area increases from 41.6 to 50.8 mph. This change has a clear and dramatic effect in the performance of the freeway.