The Analysis of Travel Demand

This chapter introduces urban travel demand models and discusses data-collection procedures, model specification, model calibration techniques and model verification. It describes aggregate models based on zonal data and behavioral models based on individual data. Information-gathering and the coding of data are important parts of urban transport planning and this aspect of the systems approach absorbs, typically, from one-half to two-thirds of the total budget. Urban planning authorities conduct a range of land-use surveys, but it is uncommon for the data collected to be made available in a form suitable for further analysis. Data collected from sample surveys are multiplied by an appropriate expansion factor to represent the whole population. The purpose of traffic generation modelling is to develop equations that estimate amount of traffic generated by zones. Model validation investigates how accurate the estimates from a calibrated regression model are when compared with observed data, and checks to see whether best combination of explanatory variables is included in model specification.