Station 4: Understanding how traffic operates

Microsimulation models allow us to understand detailed operational aspects of our transportation system. We can examine how traffic flows on a segment of highway, around a sharp curve, or through an intersection or interchange. While the regional model looks at overall demand, microsimulation models focus on the interactions and behaviors of individual vehicles. With these models we can answer questions such as:

• How, why and where does congestion occur?
• What would happen if we changed X?

This video depicts 6 minutes of the "Existing Condition" AM and PM peak hour VISSIM simulation models of the I-81 Viaduct. The purpose of the VISSIM simulations is to quantify existing traffic operations on an average day, and provide a calibrated base model which will be used to analyze future improvement alternatives. The AM and PM peak hour VISSIM simulations are each one-hour in length; however, this video contains 3-minute clips recorded from the mid-point of the full simulations in order to highlight the existing operational deficiencies.

It is important to note that traffic conditions may vary on a daily basis due to a variety of factors. The AM and PM peak hour VISSIM simulation models used to develop this video provide a representation of traffic operations on an average day. The simulation models were developed from, and calibrated by, field data that was collected in 2010.