Could Shoup be WRONG?

Most of the support for Don Shoup’s theories is based on the concept that 30% of all cars driving in the city are actually looking for parking and if they took the first available spot, it would cut down traffic by a third thus saving whales, polar bears, and a lot of gasoline.

In fact, many of the parking programs like SF Park, and others, justify, either in whole or in part, on this 30% reduction.

I had dinner the other night with a parking guru who said, in essence  “balderdash.” He told me that he had personally done a survey and he thinks the real number is like 2%. He said that you can’t just follow cars and somehow determine which are looking for space and which are driving directly to their parking destination.

You must first categorize the cars.  In other words, have they passed their location and are beginning a search. In other words, you must actually interview them after their park and find out where they were going. If you don’t do that, how could you know whether they were wandering aimlessly or they were focused like a laser beam on their destination parking spot?

He told me that he actually did this, informally. He followed a set number of cars (I think over a few weeks about 200 and actually asked the driver what their destination was. The response in the vast majority of cases was that they were going to the building adjacent or very near their parking space. He noted that they didn’t circle back looking for space, but found a space and parked. He did this as a part of a traffic survey he had done for a major US city.

My friend admitted, after a few adult beverages, that his method wasn’t the most scientific but commented that students standing on rooftops in Westwood near UCLA had little more idea of where people were going or who was cruising and looking.

He added that this number is too critical to how parking programs are approved to be left to a number that was perhaps a SWAG (Scientific Wild Ass Guess) estimate. He felt a grant needed to be garnered and a true survey done with actual interviews of drivers after they parked.

I have sent this to Don and asked him to respond.



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One Response to Could Shoup be WRONG?

  1. Paul Barter says:

    I agree to some extent. There has been a lot of sloppy quoting of the 30% thing!

    But it is not as bad as you imply here. Cruising for parking CAN cause a huge mess, especially in busy areas, at busy times, and especially when parking is mismanaged.

    How much traffic is cruising for parking? Well, it depends. Often there is no cruising for parking. But at the places where it really matters, there it is potentially a LOT of cruising (sometimes more than 30% of traffic).

    I tackled this question too: http://www.reinventingparking.org/2013/10/is-30-of-traffic-actually-searching-for.html

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