The theory of "Induced Demand"

The theory of “induced demand” goes like this: When you build a road people like it; they then use that road to do things like go for dinner, go the the gym, visit their family, etc. You have "induced demand" to use the road. If you then reduce the capacity of that road, initially a massive traffic jam is formed. People quickly learn that the road is basically impassable at certain times and decide not to take trips. The traffic then “disappears” and city planners rejoice.

It's all fine so long as you consider people going about their daily lives as valueless. I realize the city can't score the value of visiting an elderly parent. So when that trip now takes too long after work and some one gives up on seeing their parent, nothing has been lost from the city's perspective. If you assume that most people leave their house for some purpose that they consider enriching, then the loss of mobility is a loss to their standard of living. Some people can and will use other forms of transit, but a large number, for practical reasons, will not.

A proper government collects taxes and deploys resources to protect and enhance the lives of residents. These roads expanded in the first place because large groups of people voted with their time and money to use them. Congestion is created because local governments have not managed growth responsibly. To then try and convert the failure to provide services to the tax payer into some noble purpose is simply intellectually dishonest. We all certainly want the ability to get around in any way we choose.

If the focus was on providing transportation options that were better than roads, then the conversation would be quite different. It would be about changing roads that anyone could see were under used. Well designed "Road Diets" demonstrate that extra capacity is not needed. However “induced demand” often comes up when talking about changing roads that are clearly at or even well above capacity. In the minds of the proponents of this idea part of the “good” is the fact it causes disruption.

If you would like to change the way people travel, then build compelling alternatives. If you see large trees, wide walkways and lots of greenery, people are walking in that space automatically. This is because a park has been designed to be enjoyable to walk through. A road has been designed to be fast to drive through. Stop pretending some magic formula combines the needs of both traveling groups. You are enhancing the space for one at the cost of the other. The mark of great “Walking Cities” is that large areas are set aside exclusively for pedestrian travel.

The solution is to build separate pathways and areas designed for pedestrian travel. Cities where people walk also have compelling places for people to walk and local things reachable on foot. Simply trying to prevent people from traveling in a way they like and hoping they choose the method you prefer is folly. Instead of wasting energy in a combative struggle against motorists, we should be proposing and building new compelling travel systems. If what you are proposing is compelling enough to attract a large audience, even the motorist is happy because this eliminates congestion that delays them.

This is how you get a positive result for all and everyone is happy.

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  • Alexia Salgado
    commented 2016-03-28 06:21:32 -0700
    The post is really cool and I could pick up important points that had not been cleared up on other sites.
  • Elect Greg Woodruff for Burlington Mayor posted about The theory of "Induced Demand" on Elect Greg Woodruff for Burlington Mayor's Facebook page 2014-07-28 13:02:05 -0700
    The theory of "Induced Demand"


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