Chapter 4 - Transportation Demand Management (TDM)

Introduction

Traffic calming is used to slow down vehicles, and to some extent, make them choose other routes of travel. But we can take a step farther into reducing the negative side affects of motor vehicles by reducing the use of motor vehicles altogether. This is achieved through a concept called, "Transportation Demand Management"(TDM).

Transportation Demand Management

TDM is a means of pulling people out of their cars and into other means of mobilization. It even encompasses new ways of land development, to eliminate extraneous trips that simply fill our streets with vehicles. The following four major strategies of TDM are explained in David Engwicht’s book, Street Reclaiming: Creating Livable Streets and Vibrant Communities.

Strategy One

The first strategy is to simply replace car trips by other modes, such as walking, cycling, or public transit. People can walk or ride to the school or work, rather than drive. They can take the bus or trolley to the store, and leave their car at home. Not only do you remove cars from the road, you also get exercise. Major health authorities like Health Canada have shifted their health promotion emphasis from trying to get people to exercise regularly to what they call, "active transportation." It is much easier to make a routine of walking or cycling to school or work than it is to get up an extra half our earlier to ride the exercise bike, and then sit in your car in congested traffic.¹

Strategy Two

The second strategy of TDM is to remove unnecessary trips. For example, you can combine two or more trips into one. This idea of trip-chaining or trip-bending can be applied when you save up your non-urgent trips, and make one large trip out of it. This will save all the intermediary, otherwise unnecessary trips. Another way to remove unnecessary trips is to join a carpool, or rideshare. You can do this during the week to work and school, and you can do this on weekends to different activities. If your work permits, you may even be able to remove unnecessary trips by telecommuting. Working from home is not only nice and comfortable, it also reduces the number of work trips you must make, and therefore, reduces the number of vehicles on the road. You can reduce unnecessary trips by phoning ahead to stores to see if they have the product you want. This will save the extra trips of running around from store to store in hopes of finding your gem.²

Strategy Three

A third strategy of TDM is to reduce trip lengths. This can be achieved most easily by shopping and employing locally. If you think carefully, or use the yellow pages, you may be able to find what you need in local shops. Shopping locally not only eliminates long drawn out trips to distant stores, it also keeps money in your direct area, helping feed the local economy.³

Strategy Four

The fourth and most creative strategy of TDM is to reuse saved space. Reducing car use saves valuable road and car parking spaces, which can be used for things other than transporting people. Reallocating this space for the community to gather and children to play enhances the livability of the community. Parking spaces, particularly in local shopping centers, could be reused to create a greater range of facilities closer to people's home and work, thus reducing the need to drive. A remarkable statistic by researchers in Brisbane shows that cars consume three times more space than the home of their owner. Just imagine if this space was reallocated for the use of the community.⁴

Innovative TDM

TDM is an effort to shift the emphasis from the vehicle to the area the vehicle travels through. If TDM is successful, bicycles and pedestrians will have priority on residential roads. Communities will be closer nit, and extraneous trips will be eliminated. Innovative TDM is a look into the future of traffic and traffic calming. There are already many TDM success stories.

First Success Story

Australia introduced the concept of “individualized marketing” in 1997. The idea was quite simple: households were contacted and offered advice about the journeys they make. If the households were interested, the German based consultancy, Socialdata, would generate alternatives to using the car. An initial trial of this program involved over 800 households in South Perth. The study showed a 10% drop in car journeys and vehicle miles traveled, and the use of public transportation, walking, and cycling rose. Surveys a year and also 18 months later showed these shifts were sustained. Two years ago, the Western Australia’s Department of Planning and Infrastructure extended the study to over 8,000 households in South Perth. The results were even better than before, showing a 14% drop in car journeys and vehicle miles traveled. Again, there was a shift to public transportation, walking, and cycling. Local shops and services experienced an increase in business, air pollution fell, and bus companies gained enough extra revenue over three years to pay the cost of the study.⁵

Second Success Story

Within the City of Boulder Colorado 60% of the residents of hold city bus passes because of the unique approach proposed by Bob Whinston, an engineer for the city of Boulder. Whinston says his approach is simple: the riders choose their bus service. It was not chosen for them. Quite literally, riders choose the bus routes and pickup spots, the size of buses, the design, the seating plans and upholstery, the size and tinting of windows and options like hanger straps and bike racks. In addition to this customized approach, developers of new residential subdivisions are required to purchase three years’ worth of unlimited transit passes for each household at an average cost of fifty dollars. Remarkably, traffic congestion has not increased despite a surge in area housing and employment.⁶

Third Success Story

The Portland metropolitan area holds over 1.3 million people in a compact region, only 35 miles across at its widest point. The region has grown by more than 24% in the last 20 years, and employment has doubled from 63,000 in 1970 to 108,000 in 1995. Remarkably, with all the new developments, the region has only grown 13% in land area. This is the result of diversification of the housing market with land-use initiatives encouraging compact communities. The region has adopted a growth concept promoting minimal expansion of the existing Urban Growth Boundary, increased densities in centers and along transit corridors, multi-modal accessibility, and protection of neighborhoods, parks, and green spaces.⁷

Conclusion

These success stories are just a glimpse at what could be done to further the idea of TDM. Hopefully more cities and even states will adopt the idea of TDM into their future planning. We can use the state of Oregon as a role mode, which adopted a Transportation Planning Rule to increase accessibility, require pedestrian and bicycle facilities, and require reductions in vehicle miles traveled and parking spaces per capita.

References

1. Engwicht, David. Street Reclaiming: Creating Livable Streets and Vibrant Communities. New Society Publisher, Gabriola Island, British Columbia, 1999, 65-68
2. Engwicht, David, 69-70
3. Engwicht, David, 71
4. Engwicht, David, 73-75
5. Jowit, Juliette. “When 8,000 Perth Households Were Helped to Analyze Their Journeys, Car Use Fell by 14 Percent With a Shift to Public Transportation and Cycling.” Financial Times 11 September 2001
6. McKay, Paul. “How the continent's best transit works: A maverick city bus manager decided to do what virtually no other transit agency has done in North America: Ask riders what they want, then deliver it. The results are astounding.” The Ottawa Citizen Thu 31 May 2001
7. Elaine, Wilkerson. “Land Use Management: Portland’s Positive Experiences in Curbing Sprawl.” http://www.vtpi.org/tdm/tdm71.htm

This chapter originally written by Dan Ferster, 1999, as part of a senior project.