I can’t seem to get away from this number: 30%. That’s what everyone thinks the number of people cruising for parking on any given moment in any given city. But where did that number come from – the answer of course is Don Shoup.
The good professor sort of referred to that number in his first book, “The High Cost of Free Parking” and it stuck. Cities far and wide have been using it to justify everything from increasing parking fees to hiring new enforcement officers. But is 30% the real number? What if its 40%? or 20%? or even 10%? Would decisions made by parking planners differ depending on that number? I would think so.
Don has been ignoring the controversy, but now it gets real. Harper’s magazine is publishing it as fact, quoting Don, in its “Harper’s Index” section which is basically a list of of pop culture numbers derived from everything from polling to the FBI to a group called “Knife Rights” to well, Don Shoup. Do you know that the portion of men in the US who don’t believe its important to change their underwear daily is 1/5. Do you care? That’s the kind of “click bait” Harper’s lists. But I digress.
Technically, Don never actually said that 30% was a hard and fast number. From his current book:
Six of the 16 studies estimated the share of traffic that was cruising for parking, and the average share was 30%. I carefully qualified the estimates in the table, and did not say that 30% of all traffic was cruising. Two of the estimates were above 30% and three were below. Nevertheless, some readers seized on the 30% figure an easy way to suggest the problems caused by cruising for parking.
Unfortunately in the real world, its not what you actually say, its what people hear and then believe. I doubt if there are more than six people on the planet who, when asked the cruising number, won’t say 30% and most will say because Don Shoup says so.
In his new book Parking and the City, Don spends a chapter attempting to unwind this 30% number with tech, documents, and graphs. His manuscript attempting to clarify the history of the number will be printed in the February issue of PT. What follows is the last paragraph of the manuscript:
As more cities install cameras to analyze traffic patterns, they should be able to make real-time estimates of the share of traffic that is cruising for parking. Until then, suppose you had to guess what share of the traffic on a congested downtown street with underpriced and overcrowded curb parking is cruising. About a third seems a reasonable guess.