Today, more than half the people on earth live in urban areas. By 2050 that number is projected to reach 66 percent. That’s 2.5 billion or so people squeezing into the world's cities. Now imagine even 10 percent of those people have a car. That's another 250,000,000 vehicles.

The world has time to rethink city planning before gridlock becomes truly disastrous. Fortunately, automakers are coming around, and some even consider solving this problem a priority. Audi believes self-parking cars are part of the answer.

Under its Urban Future Initiative, the German automaker is working with the Boston suburb of Somerville to develop new ways of moving people around and reconsidering how cities are designed. "The car shaped the city in the 20th century, and in the 21st century the city will shape the car," says Christian Gärtner, who is part of the project and a board member at the architecture and design firm Stylepark AG.

In Somerville, Audi will help develop a connected network of traffic lights in the busy Union Square area to reduce congestion. More tantalizing is the rest of the plan: introducing cars that park themselves. Audi is working with a real estate developer to incorporate autonomous car tech in a program meant to drastically reduce the space lost to parking and the congestion caused by people trolling for a spot. In a 2011 study published in Access magazine, UCLA urban planning professor Donald Shoup found 30 percent of the traffic in a downtown area is simply people looking for parking.

The environmental ramifications are enormous. Shoup cites a 2008 study, conducted in a 15-block span of Manhattan’s Upper West Side, that found each driver spent an average of 3.1 minutes searching for parking space and covered an average distance of .37 miles. Extrapolate those figures, and Shoup says people roaming those 15 blocks alone created 366,000 excess vehicle miles of travel—that's equivalent to 14 trips around the planet—and added 325 tons of CO 2 in one year.

Cars that park themselves help a lot. If your car can leave you at your destination and return for you later, it doesn't matter where it parks. If it knows there's a garage with available spots 10 blocks away, it can go straight there, minimizing the time it spends taking up space on the road.

That's why, come 2018, Audi will deploy a small fleet of cars to see how its piloted parking technology interacts with a garage designed specifically for autonomous cars. With no one getting in and out of the cars, the space needed for each vehicle is reduced by 21 square feet. You need just four inches of space between mirrors on neighboring cars, since they will park themselves with machine-like precision (because they’re machines). No elevators or stairs or pedestrian pathways are needed, either. Audi estimates such a lot could pack 60 percent more vehicles than a conventional garage of the same size.

Phase two is slated for 2020, when the goal is to have a fleet of autonomously parking Audi cars in the area. And by 2030, Audi hopes to make the garage available to the broader market of self-driving cars expected to hit the market by then. “We want to be the first ones to test this and find out what the potential is and to get into context with new business partners. But these are things that need to be open at a certain point," says Lisa Futing, the initiative's project manager.

Drivers seem to be onboard with the idea. In a study of 5,600 people in 10 countries by the World Economic Forum and Boston Consulting Group, nearly 60 percent said they'd feel fine riding in a self-driving car. More relevant here is that 43.5 percent of them said the biggest benefit of such technology is letting the car park itself.

Audi's not alone here. Uber is working with Carnegie Mellon University to test self-driving cars in Pittsburgh. In 2017, Sweden will put 100 self-driving Volvos in customer hands and on public roads. General Motors has launched car sharing programs in Manhattan and Germany. This is all part of "mobility"—the catchall term automakers use to acknowledge that selling individual cars to individual people won't work forever, at least not in cities.

Down the line, Audi's looking at car sharing services that would allow for cars to be used more efficiently on the road as well as in the garage. The company estimates the average car is used just 5 percent of the time. The rest of the time, it's sitting there, depreciating. That has Audi pondering a scenario in which commuters use cars in the morning and evening while business customers drive them during the day. Futing says such programs could lead to garages moving out of downtown areas entirely in favor of transit hubs where people leave their cars to park themselves in remote areas. This, presumably, would create more room for pedestrians and cyclists.

If we really are on our way to Judge Dredd-style MegaCities in the future, we're going to need more projects like these. And if Somerville pans out for Audi, let's just hope other automakers are cooking up big ideas, too, because it's way past time for our cars to actually run our errands for us too.