Sub-Problem 3b: Using a Microscopic Simulation Model

CORSIM produces a very detailed output, covering several measures of delay and travel time, as well as other measures such as vehicle emissions and fuel consumption. We will consider the average control delay measure, similar to the measure produced by the HCM signal model.

The results from the CORSIM simulation model are shown in Exhibit 1-35. We've also included the results from the HCM analysis for easy comparison between these two models.

Exhibit 1-35 shows that there are some significant differences between the estimates of average control delay produced by the two models, HCM and CORSIM. While we have no way of verifying the quality of either estimate, we can say that CORSIM and other similar microscopic simulation models have the potential to produce more realistic results. Why? Because the microscopic simulation models are better at accounting for the microscopic interactions between vehicles, they are more likely to better represent conditions of oversaturation than the macroscopic approach taken by the HCM. But this is true only if the model is correctly coded, calibrated, and applied (including multiple runs to account for the stochastic nature of the simulation). Our major advice is this: if you are dealing with conditions in which demand exceeds capacity, queues from one intersection interacting with an adjacent intersection, intersections that are closely spaced, or multiple time periods, you should consider the use of a microscopic simulation model to produce estimates of control delay. Just like the HCM procedures, use of any microscopic model requires special care and expertise to assure that the accuracy of the results is commensurate with user expectations.