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

Note that the during the PM peak, v_R12 is 5,265 passengers cars per hour, a flow rate which exceeds the capacity of the merge influence area (4,600 pc/h). The implication is important: a significant part of the demand (5,264 - 4,600 = 664) can't be served during the analysis period. This unserved demand is diverted to the next analysis period. The density during the PM peak is 42.4 pc/mi/lane, while the speed is forecasted to be just below 42 mi/hr.

What is the basis for the forecast of level of service? The basis for forecasting level of service is the density of traffic flow. For this case, the density during the PM peak is 42.4 pc/mi/lane, which is level of service F. The level of service during the AM peak is B, based on a density estimate of 13.7 pc/mi/ln.

How would you describe the operation of the merge point in the PM peak period? The operation of the merge point during the PM peak period is poor. The demand exceeds the capacity, the density is high, and the speed is relatively low. Since the demand exceeds capacity, we need to consider another analysis tool, such as a microscopic simulation tool, that will enable us to have a more accurate characterization of the operational performance of this ramp junction during the PM peak period. Remember that the HCM states in chapter 25 that this methodology does not take into account oversaturated conditions. The use of micro-simulation will be illustrated in problem 5 of this case study.