Problem 5: Network Simulation

Printable Version

This problem demonstrates how a network simulation model can be used to augment studies conducted with HCM methodologies. Simulation models offer the advantage of being able to examine networks of highway facilities in a highly unified, holistic fashion. Inter-dependencies and cascading effects can be taken into account as can traffic variations of time, over saturation, queue length fluctuations, lane blockages, and other transient phenomena. The only major drawback is that simulation models are typically data-hungry and they take time to develop, debug, calibrate, validate, and run. Distilling the results also takes time, because there’s so much information to study, absorb, and comprehend.

Two main decisions need to be made: 1) what network to analyze and 2) what traffic volumes to use. Exhibit 4-77 shows the network used as the basis for the simulation model. It encompasses Alternate Route 7 and the interchange complexes at either end: Exits 6 and 7 on I-87, the interchange with Route 9 on Route 7, and the interchanges with Route 7 and 23rd Street on I-787. What it doesn’t include is the underlying surface arterial network and the freeways that lie outside the artificially defined boundary. The actual simulation network is detailed, with information about lane configurations, vertical and horizontal geometry, speed limits, etc.

The time period we studied was the AM peak. Either the AM peak or the PM peak would be a good choice. The only difference is the direction of peak flow. In the AM Peak, the flows are predominantly southbound and eastbound.

Discussion:
Take a few minutes to consider these questions. When you are ready to continue, click continue below to proceed.