Transportation Demand Management (TDM) Policies

Transportation Demand Management (TDM) describes the use of one or more strategies designed to encourage more efficient use of transportation systems, most notably to reduce the use of private vehicles, especially at peak periods. TDMs are numerous and address everything from transportation modes to the time at which trips take place. However, the most influential strategies involve adjusting the cost and/or supply of specific transportation-related factors. For example, a combined approach of reimbursing the cost of transit and reducing free off-street parking may result in more people switching from private vehicle trips to transit or other non-motorized mode trips.

While no single TDM strategy significantly impacts the proportion of walking, bicycling, or transit trips, an integrated suite of strategies can produce worthy results. As such, many MPOs and local governments have adopted TDM policies for large employers, including themselves, in an effort to meet government environmental standards (i.e., Clean Air Act air quality standards for ozone and fine particulate matter), congestion objectives, and other transportation-related goals. TDMs are likely to play a major role in influencing travel patterns as transportation's role in contributing to global warming becomes quantified and increasingly visible.

The following TDM strategies are just a few that may influence the proportion of walking trips:

  • Parking policies that increase the cost of parking or reduce the supply of off-street parking encourage patrons to consider using modes other than private vehicles.
  • Financial incentives to use modes other than the private vehicle encourage their use. Incentives may be formed as parking cash-out programs, off-street parking fees, pre-tax transit reimbursements, subsidized transit, or some combination.
  • Unbundling parking spaces in new residential developments gives buyers and renters the opportunity to purchase only the amount of parking they need, which may lead to fewer overall parking spaces and the associated vehicles. Studies show that fewer vehicles per household reduces vehicle miles traveled and increases the use of modes other than the private vehicle.