For example, parking demand generated from an office building is usually estimated based on usable floor area, factors for employees and visitors per unit of floor area, and the percentage of employees and visitors using cars to get to the office. In other cases, the number of students in a college or number of chairs in an auditorium can serve as a basis for estimating the demand for parking. The classic survey of this sort is published by the Institute of Traffic Engineers (USA) “Trip Generation Manual” now in its 9th edition.