This chapter introduces the topic of transportation demand and its determination. Transportation demand, simply stated, is the demand for trips that exist in any area. All of this demand, however, may or may not materialize into physical trips (vehicular or pedestrian) -- and some of it generally remains latent and is referred to as hidden demand. The importance of analyzing the transportation demand in order to be able to predict the expected number of trips in a given network cannot be overstated. The demand for transportation forms the primary input in any decision related to creation and management of transportation and traffic facilities, like roads, intersections, parking lots, transit system, etc.
The chapter is divided into three sections. The first section describes the nature of transportation demand and how it can be analyzed. The second section presents the sequential demand analysis technique -- the most frequently used method of determining transportation demand. The third section briefly describes some of the data collection mechanisms employed in travel demand analysis.