Transportation Demand Management: Anything to Avoid Confronting Convenient Driving Directly

Transportation Demand Management , often known as TDM, is an approach to transportation planning which generally seeks to influence travel behavior by changing the "demand" for driving. TDM is the type of program that planners (and consultants) love--it sounds good, gets the public excited, it's paid for by someone else, and is often innocuous enough to not do anything that makes anyone angry (or have any real effect). TDM Strategies often include a mixture of:

Many of these are fine, but they are mostly "carrots" rather than "sticks"--and in facilitating real change, the majority of them are just not that effective. Think back to your own experience--have any of the items above ever significantly influenced you to change your travel behavior? Would they be effective on your colleagues?

The only items from the lists above which really produce any results are the ones that address transportation supply: pricing roadways, reallocating right-of-way space, and pricing vehicle storage space (aka parking). This is because when the supply of a certain type of travel like is cheap and convenient, people consume more of it. When the supply of that same type of travel becomes more expensive or less convenient, people use less of it. Showers for bicyclists, marketing campaigns about clean air, and apps which show when your bus will arrive just do not materially impact the decision making process of the person who lives far from work and drives in every day because they don't change the factors that make driving convenient. Change the cost of a driver's commute, however, and you will probably see results (if the higher prices persist in the long term ). That's why Transportation Demand Management should really just be Transportation Supply Management: focus on transportation supply like roads and parking, and cities can leave the other pieces to whomever.

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