Large and complex highway planning exercises often use travel demand forecasting models to help analyze the need for alternative highway investments. For Phase 1 of the US 64-NC 49 Corridor Study, the study team developed a transportation model as a forecasting tool that would be capable of producing reliable, order-of-magnitude estimates of both the potential increases in travel demand across the study area resulting from projected population and employment growth and the potential traffic diversion effects of providing additional highway capacity along the US 64-NC 49 Corridor. For these and other measures of effectiveness, the sketch-planning forecasting tool supplied information to confirm the need for congestion and mobility relief in the corridor and to judge the relative merits of the alternatives studied in addressing these needs.

The model was constructed to capture changes in longer-distance (inter-urban) flows of autos and trucks that result from significant changes in highway capacity, household growth, and employment growth. In contrast, transportation models developed and used by Metropolitan Planning Organizations such as those in Metrolina, Triad, and Triangle areas, are designed to capture traffic demand within a metropolitan region. They are designed to capture the impact of small scale changes in travel times and costs on travelers' mode of travel, their choice of routes, and their choice of destination.

Land use was represented as aggregated areas corresponding to 2000 US Census tract geography in a 24-county core model area and as entire counties in the rest of the state. In all, there are 904 traffic analysis zones, of which 740 lie within the core model area. The highway network in the core area includes most roadway facilities up to and including the major collector functional classification. Outside of the 24-county area, the highway network includes only primary arterials such as the Interstate Highway System.

Observed traffic counts and a simulation of 2002 traffic were used to assess the utility, reliability, and validity of the model as a forecasting tool. Numerous corrections and adjustments to the highway network's configuration were made as a result of these comparisons. In addition, a utility program in the modeling software package (TransCAD) was used, which adjusts the number of trips between origins and destinations so as to produce the best possible traffic assignment match to the traffic counts.

View the Model Calibration Report (756 KB).