Next time you're searching for a parking space and someone grabs a spot from right in front of you, it might seem like the last space left on Earth, but ponder this: there are at least 500 million empty spaces in the United States at any given time.
The 250 million cars and trucks on America's roads get a bad rap for being environmentally unfriendly. Climate scientists say that automobiles add an array of greenhouse gases and harmful particulates into the Earth's atmosphere, yet little research has been done to estimate the impact parking spaces -- where those automobiles spend 95 percent of their time -- have on our planet.
"I think it's a surprisingly unknown quantity," said Donald Shoup, a UCLA urban planning professor and author of the book "The High Cost of Free Parking." "[Parking] is the single biggest land use in any city. It's kind of like dark matter in the universe, we know it's there, but we don't have any idea how much there is."
Civil engineers at the University of California, Berkeley recently published the first comprehensive estimate of parking spaces in America and found that the energy use and materials associated with creating hundreds of millions of parking spaces has a significant environmental impact.
The group had already published a study aimed at finding the environmental impact of America's total transportation infrastructure, but when they tried to estimate the impact of the nation's automobile infrastructure, they were forced to use the only existing national parking spaces study -- a count of just the 100 million metered parking spaces in the United States. A number of other environmental engineers were quick to call out the obvious limitations of using such a small number and convinced the team to attempt the first ever nation-wide count of parking spaces.
"We got some feedback from people saying 'We think you guys are drastically underestimating the amount of parking spaces in the United States,'" said researcher and lead author of the study Mikhail Chester.
Chester pointed out that if there are 250 million cars in the country, obviously there must be at least that many spaces for people to park at home -- add in spaces for work and shopping and it becomes apparent that there must be many times more than 100 million parking spaces. The researchers' estimates included things like street side parking, building code requirements, parking garages, lots in megastores like Walmart and Target and then parking spots at work and home.
Even defining a parking space is a difficult task, so the group focused on several primary groups of paved spaces; free and metered on-street spaces; surface parking, or ground spaces like those found in front of big box stores and in people's driveways; and multi-story parking structures.
Because of all the uncertainties, they decided to examine the environmental impact of five different scenarios for parking. The first scenario was limited to only the 100 million metered parking spaces in the previous study. The next three scenarios examine what the group considers to be the most likely situation -- that there are somewhere around 800 million parking spaces in the United States, or nearly three official parking spaces for every car on the road.