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A new analysis of 27 mixed-use areas finds that parking in U.S. metro areas is, on average, oversupplied by 65 percent.

When we say we can't find anywhere to park, what we usually mean is we can't find a free or insanely cheap parking spot within spitting distance of our destination. As a nation of parkers we're all home run hitters who've forgotten what it's like to knock a single—or, as a closer metaphor, to draw a walk. The result is a misperception that parking is scarce despite the great deal of lots, street spaces, or garages that might exist a block or two away.

Some new research reminds us just how oversupplied parking really tends to be in American metro areas: in a word, enormously. Rachel Weinberger and Joshua Karlin-Resnick of Nelson\Nygaard Consulting Associates analyzed parking studies of 27 mixed-use districts across the United States and found "parking was universally oversupplied, in many cases quite significantly." On average across the cases, parking supply exceeded demand by 65 percent.

"You see a huge amount of land dedicated to parking," said Karlin-Resnick, who presented the work Tuesday at the 94th annual meeting of the Transportation Research Board. "That land, particularly in downtowns, could really be dedicated to more active uses, economic generators, and by extension tax generators."

The researchers focused on districts with both residential and retail developments in a variety of settings—17 suburbs, 6 cities, and 4 towns—mostly in New England or California. (Interestingly, a third of the areas were documented as having the impression that local parking was scarce.) By looking at previous parking studies in these areas, as well as satellite imagery via Google Earth, they identified existing parking supplies and peak weekday and weekend demands.

Critically, the researchers also took into account the accepted practice of supplying 15 percent more spaces than necessary—a sort of buffer zone that reduces the congestion caused by drivers circling for spaces.

In all 27 districts, spanning places with 420 spaces to those with 6,600 spaces, Weinberger and Karlin-Resnick found an oversupply of parking over and above the buffer zone. The oversupply ranged from 6 percent up to 253 percent across the study areas (below, the highest over-suppliers). And in the nine areas that had believed parking to be scarce, the oversupply ranged from 6 percent to 82 percent.

CityLab

Surprisingly, Weinberger and Karlin-Resnick found no connection between parking oversupply and several local factors that might explain the trend, such as region, area type, commute mode, and parking cost. Instead they found oversupply to be the norm in West Coast areas designed with cars in mind as well as in East Coast districts designed around transit, and in suburbs with higher driving shares as well as in cities with lower ones. They also found that the oversupply trend held true in mixed-use districts with paid parking as well as in places where parking was free.

In other words, the tendency to supply too much parking seems to rest above the shifting winds of local behavior. Here's Weinberger and Karlin-Resnick in a write-up of the research:

Though it would be appealing to have a "scientific" or "engineering" basis for determining appropriate parking supply, the evidence here suggests that levels of parking provision are unmoored from demand, travel behavior, pricing or other dimensions where theory suggests there would be a relationship.

As for why parking supply tends to outpace demand so dramatically, a number of reasons might apply. Planners have been known to copy parking codes from other nearby cities rather than identifying specific local needs. And business owners retain the (often outdated) mindset that their sales depend on an abundance of adjacent parking. Mandatory parking minimums for developers no doubt play a role, too.

Weinberger and Karlin-Resnick suspect another major factor is risk-aversion. Public officials (and, by extension, the planning staffs they assemble) might view any undersupply of parking as such a political risk that they compensate by providing way too much. And since the costs of providing parking are distributed widely among taxpayers or businesses, or hidden in the decision not to build a mixed-use development at all, officials are inoculated from the consequences.

"The costs of oversupply really aren't felt," said Karlin-Resnick. "That's perhaps what drives the picture we're seeing in a lot of these places."

And of course the flawed belief, felt most acutely as we circle for a homerun spot, that oversupply doesn't really exist.

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