Overview of the TDF Process

Travel Demand Forecasting is a multi-stage process, and there are several different techniques that can be used at each stage. Generally, Travel Demand Forecasting involves five interrelated tasks.

1. Break the area that requires prediction of future travel demand into study zones that can be accurately described by a few variables.
2. Calculate the number of trips starting in each zone for a particular trip purpose. (Trip Generation Analysis)
3. Produce a table of the number of trips starting in each zone and ending up in each other zone. (Trip Distribution Analysis)
4. Complete the allocation of the various trips among the available transportation systems (bus, train, pedestrian, and private vehicles). (Modal Choice Analysis)
5. Identify the specific routes on each transportation system that will be selected by the travelers. (Trip Assignment Analysis)

Once these five steps have been completed, the transportation engineer will have a clear picture of the projected travel demand for an existing or proposed transportation system.