Tuesday, April 8, 2008

Inducing Demand

If you’ve never heard of the term Induced Demand before here is a crash course when it comes to transportation. Induced demand is the observed increase in traffic or passenger volume that occurs soon after a new highway or transit system is opened, or a previously congested highway is widened. The US Federal Highway Administration has an interesting FAQ on the subject. You have to realize that they are a highway building organization, and therefore have a bias. There is even something called Reduced Demand which is Induced's inverse. Check out this Wikipedia article for more information.

Now what does all the inducing, and reserves inducing, having to do with anything? Well you have to ask yourself; where do you want to be inducing traffic? Do you want it on new roads, or do you want it on new transit systems? I would hope that you would want it on new transit systems. We have seen induced traffic on transit systems all over North America where new lines are built. Whenever Calgary builds a new extension to their system, they end up with more passengers.

I used to live in Calgary and was at the end of the south LRT. When a new southern extension opened, I was no longer at the end of that line. Crazy, eh? Anyway, I usually never had to skip a train because it was packed. But after the opening, I always had to wait a train or two until I could get on. The station I was at was as busy as it ever was, and the new stations were busier than ever too.

When you induce travel on roads, you end up with more people on the road, which means more pollution, and eventually congestion. Gordon price has a good post on his blog about it.

As for examples of the inverse: when they removed the Embarcadero Freeway in San Francisco after an earthquake in the 90’s, they noticed that the traffic it used to carry disappeared. Not onto other roads, it just disappeared. Remember when 1st in Vancouver was closed a few years back? The world didn’t come to an end there.

If we care about the environment and the economy, we must have a balanced transportation system. We already have the roads. Let's induce transit, and price roads. This will help relieve some congestion and give travelers better transportation option.

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