Transportation demand management
Transportation demand management (TDM) refers to ways of making the capacity of our roads more efficient by reducing vehicle demand. TDM approaches consider how people’s choices of travel mode are affected by land use patterns, development design, parking availability, parking cost, and the relative cost, convenience and availability of alternative modes of travel. Various TDM strategies are used to influence those factors so that the alternatives are more competitive with driving alone and potentially reduce reliance on motor vehicles.
To create and maintain an environment in which there is less reliance on motor vehicles takes actions from both public and private parties. In its TOD program and other efforts, King County is looking for developers to make a positive contribution to such an environment.
TDM strategies at a development can be divided into two basic categories.
- Pre-occupancy: things that need to be done while a development is being designed and built, and
- Post-occupancy: things that can be done once people are using the development.
The pre-occupancy actions are critical because they are most likely to determine how attractive, convenient, and safe alternative travel will be once the site is occupied. Before a site is occupied, or during a remodel, it can be designed to be convenient and safe for pedestrians and bicyclists, and vehicle parking can be provided to meet but not exceed demand.
After the development is built, incentives can be offered, but those incentives will not work as well if the site and its surroundings are oriented to cars. The incentives generally include subsidies to use transit or rideshare, information about where and how to use alternatives, and possibly back-up services in case a regular transit or rideshare arrangement isn’t available for a particular trip.
Where TDM is applied
TDM strategies are often applied at employment sites, such as, through the Washington State CTR law, at major institutions such as the University of Washington and Group Health Hospital. There is extensive experience and research related to commute-related TDM through work sites.
TDM is also being applied in residential settings, including at transit oriented developments. In a residential setting, there are additional ways to help residents connect with each other and their surroundings to get to and from work, school, shopping, kids’ activities, transit centers, and other travel destinations.
Examples of TDM
Pre-occupancy—site design considerations
One of the most influential long-term factors in trip choice is the physical environment. How comfortable does it feel to walk to and from the site and within the site—for mobile adults, for a person alone, for people with mobility limitations, for families with kids? How far is it to a mix of services (transit stop, groceries, bank, medical offices, drug store, school, employment, etc)? How easy is it to get to those services on foot, by bicycle, by transit? Does the site feel isolated from or integrated into its surrounding community? Does it feel like the site and its surroundings are designed for cars or people? Are there major barriers that impede easy or safe pedestrian access, such as large parking lots, fences, multi-lane roads, or circuitous pathways?
Examples of site design elements that promote alternative modes:
- Sidewalks that are safe, attractive, and well-lit, and that directly connect main entrances to the primary street or activity area without barriers.
- Main building entrances that are oriented to the main street or activity area, and are not separated from the street by vast parking areas or fences.
- Primary parking that is located away from the main pedestrian entrance, with drop-off or short-term parking near the main entrance to replace the need for a front-door parking lot.
- Safe bicycle access toward area services and bike routes, with signs for bikes and motorists and a marked lane or path.
- Direct, safe, well-lit paths to the nearest transit stop.
- Where transit is on-site or adjacent to developments, contributions by the developments to the transit facilities, such as bus pads, shelters, signs, lighting, and trash receptacles.
Numerous studies show that the availability and cost of parking are the biggest factors in a person’s decision to drive. Lots of free parking encourages driving, usually alone. Here are some TDM considerations when developing parking.
How much vehicle parking is there—more than enough for the occupants or users? What’s “enough” parking? Can incentives be used to reduce the need and cost of constructing parking stalls? Where is the parking located? Is it individual or group parking? Do cars have better access than pedestrians and bicyclists? Can a resident park a bike where it will be protected from the weather and from theft? If residents don’t have their own garage space, do they have storage lockers for extra belongings? Is there a place for a communal workshop or repair area? Is parking “included” in the lease and do residents know the value of the parking or is it invisible?
Examples of TDM strategies for multifamily residential parking:
- Parking that is grouped rather than provided for individual units. Storage lockers, communal workshops, and repair areas provide residents with places for typical “garage” uses other than parking.
- Providing resident parking spaces equal to or below estimated demand. At multi-family residential sites, providing no more than one space per residential unit, with some additional spaces for short-term guests. Some local codes allow a density bonus in exchange for reduced parking supply.
- Parking spaces that are available to users for a fee, and which residents may trade for ongoing subsidized access to alternatives. If included in the lease, parking space costs are a separate line-item, to show the true cost of parking.
- Extra resident parking spaces (over one per unit) that are available only for a fee.
- Reserved parking space for a car-sharing vehicle (locally, Flexcar) if community demand warrants.
- Shared parking arrangements for a neighboring business whose customers/employees/visitors need parking when the site’s residents are gone.
Another factor in trip choice is the availability of, and access to, alternatives to driving alone. Because of King County Metro’s extensive experience with TDM and the CTR law, there are a variety of services and products to help make these alternatives more competitive with driving alone, at least for some trips.
Examples of post-occupancy TDM at residential sites
- Providing residents with subsidies for transit and other non-drive-alone modes, when they move in or on an ongoing basis (if ongoing, potentially as a trade for a parking fee).
- Posting information about local transportation services prominently, distributing it to all residents, and updating it regularly.
- Providing a resident “ride-board” with a map and place where residents can offer or request rides for their recurring or occasional trips.
- Providing an electronic kiosk through which residents can check transportation conditions, transit services and facilities, ride-sharing opportunities, bicycle services and facilities (routes, parking, bike station, bike-buddy matching), and other local services.
- Providing residents with a membership to the local car-sharing organization and, if local demand is sufficient, providing a car-sharing vehicle on-site.
- Ensuring that the property manager is well versed in current transportation services and opportunities, and regularly provides personal information to residents.
- Encouraging or providing formal and informal networks among residents that arrange carpools for ongoing or occasional trips for commute and non-commute purposes, including shopping, kids’ activities, etc.
Some TDM resources
- Victoria Transport Policy Institute—a comprehensive TDM resource with lots of useful links to both transportation and related land use sources throughout the world.