The goal in San Francisco is to decrease traffic congestion and the accompanying pollution. The solution: to charge a fluctuating market rate to keep metered space occupancy rates at 85%. That way, spaces are available for would-be parkers, which decreases the amount of circling for spots. This will do much to keep cars moving in and out of dense urban areas, generate significant additional revenues for the city, and encourage people to quit driving so damned much.

One of the keys to decreasing car usage, and the myriad of associated problems that automobiles bring us (pollution, global warming, health issues, expense, war to name a few) is to stop subsidizing the car. Relatively inexpensive gas (even at $3+ per gallon) and endless roads are clearly factors that make driving and car ownership more appealing; cheap parking is another.

Downtown parking spots are located on some prime real estate, and the meter rates don’t reflect the true worth of the space. Park(ing) Day brings attention to this inequity as groups temporarily reclaim parking spots and turn them into urban green space.

As we discussed in our Paradise Paved article, these spots carry hidden costs, which eventually filter back to consumers and taxpayers. So, why not just put the tariff up front on those who feel the need to drive into cities? Charge more for prime locations, and less to those willing to park away from city centers and walk into town, or to get on public transit.

In San Francisco, the prices on the electronic meters could easily be adjusted to match demand. A similar system is currently in place in Redwood City, CA where solar-powered meters are in operation. The result has been the desired turnover rate of parking spots, and increased revenue for the city.

According to Donald Shoup, a UCLA professor of urban planning, 85 percent occupancy is the magic number he refers to as the "Goldilocks Principle."

"If the price is set high, people won’t stay long; if it’s too low, people will never leave," Shoup said.