Problem 2: Analysis

We have produced a significant amount of information about the operation of the I-87/Alternate Route 7 interchange using the HCM. Let's summarize the key points from the four sub-problems we've just completed.

In sub-problem 2a, we divided the interchange into manageable components that could be analyzed using the procedures of the HCM, including both weaving sections and ramp junctions. In sub-problems 2b, 2c, and 2d, we analyzed the operation of the three weaving sections and one of the four ramp junctions. Exhibit 4-38 summarizes the results of these analyses.

Weave A, the section of eastbound Alternate Route 7 from the I-87 on-ramp to the US 9 off-ramp, operates at an acceptable level of service A during the AM peak hour and B during the PM peak hour. In both cases, we can have confidence in the model forecasts, since the model's boundary conditions are satisfied.

At both Weaves B and C, however, poor levels of service are forecasted, and the model conditions are not satisfied. We can assume that field conditions are poor with periodic queuing and delays for motorists traveling through these weaving sections.

We also forecasted levels of service for the northbound I-87/Alternate Route 7 merge point. During the AM peak, the level of service is expected to be B, certainly an acceptable level of performance. However, for the PM peak hour, the level of service is forecasted to be F. Further, the demand exceeds the capacity, implying that the HCM model should not be applied for these conditions.