What is travel demand management (TDM)? In a nutshell, TDM is an innovative concept in transportation planning whose rime supposedly carne (Ferguson 1990) and went (Giuliano 1992) in little more than of the eye. It very well may be that the importance of TDM lies not so much in what it is, but rather that which it is not. The traditional model of transportation planning focusses on physical infrastructure and capital investment. It treats transportation projects as a form of public works, nothing more. The traditional model may have as its main purpose congestion mitigation, economie development, the creation of new jobs, or the relief of unemployment. The demand for travel is treated as a purely exogenous variable, unrelated to and unaffected by any significant changes that may simultaneously occur in the supply of surface transportation facilities, such as:

streets, highways and bridges for private automobiles,

bus stops and curb cuts, rail lines and stations for public transit vehicles, and

bicycle paths and pedestrian sidewalks for nonmotorized transportation (NMT).