l. The origin-destination surveys and traffic volume counts used for years by highway planners were supplemented in the 1960s by more extensive data collection efforts, notably home interview surveys and transportation-land-use inventories. As a result, the database in most metropolitan areas today includes many different data items collected by numerous agencies and serving diverse purposes. This database is useful in the application of travel behavior models and in monitoring the performance of the transportation system so that problems can be identified and the degree of attainment of objectives assessed.