The first step in travel forecasting is trip generation. In this step, information from land use, population, and economic forecasts are used to estimate how many trips will be made to and from each zone.
Types of Most Commonly Used Trip Generation Models
Regression models: equations such as:
Total trips = 1.1*population,
Home-based work trips = 1.5*total employment, etc;
Cross-classification tables based on: household size, number of workers, income class, vehicle ownership, etc.;
Special generator models: used for generators such as airports, colleges, amusement parks, green spaces, etc.;
Separate rates for peak and off-peak trips.
Assumptions and limitations:
Pedestrian and bicycle trips are usually excluded from trip generation models.
Commercial vehicles need to be generated separately.
Care should be taken before interchanging vehicle trip rates with person trip rates.