RESTON, VIRGINIA—A Boston-based startup called Optimus Ride has launched a new self-driving vehicle service in the Washington, DC suburb of Reston, Virginia. On Monday, I traveled to the site, a 45-minute drive from my home in the nation's capital, to see it first-hand.

Since August, the company has been ferrying passengers between a Fannie Mae office building at the site and an overflow parking lot a few minutes' walk away. But Optimus Ride has much larger ambitions for the site.

The 36-acre property is directly adjacent to a new stop ("Reston Town Center") on the DC Metro system's Silver Line. The site's owner, Brookfield Properties, is planning a massive mixed-use development here it has dubbed Halley Rise. There will be new homes, office space, and retail stores—including a Wegmans grocery store.

Optimus Ride is betting that self-driving vehicles can transform the way projects like this are designed—making it much easier to build pedestrian-friendly, high-density developments far out in the suburbs.

Why walkable suburban neighborhoods are hard to create

There are fundamentally two kinds of neighborhoods: high-density neighborhoods oriented around walking and transit, and low-density neighborhoods oriented around cars.

High-density urban neighborhoods have enough foot traffic that stores and restaurants can thrive without parking lots. The lack of parking lots allows stores and homes to be closer together, which improves walkability.

Transit plays a key role here. High-density neighborhoods have a lot of people within walking distance, including many without cars, which means there's a lot of demand for transit. That allows buses and trains to run frequently, further improving the appeal of a car-free urban lifestyle.

The opposite dynamic is at work in the suburbs. Most people drive, so stores, restaurants, and apartment buildings need large parking lots. All that parking spreads things out, so walking isn't practical for most trips. With widespread car ownership, demand for transit is low, so buses run infrequently.

In large metropolitan areas, there's still significant demand for rapid transit from the suburbs into the urban core. Lines like the DC Metro's new Silver Line cater to this demand. But parking is a major challenge. Few people live within walking distance of a suburban train station, so the station needs to offer parking. But the parking lots fill up quickly, and during rush hour you wind up with traffic jams around the subway station.

Urban planners sometimes try to address this by encouraging high-density development right around suburban subway stops—essentially creating an island of urban living around the subway stop. But it's not easy. A family within walking distance of a subway stop can take the subway for some trips, but if the area around the subway stop is all car-oriented suburbs, the family is still going to need a car to travel anywhere else. That means you need a parking space—and probably two—for every housing unit. That limits how many people can live within walking distance of the station.

This problem is illustrated by the subway stop's namesake, Reston Town Center, which is on the north side of the subway line (Halley Rise is to the south). I had lunch at Reston Town Center prior to my Optimus Ride visit.

Reston Town Center is a high-density mixed-use development much like Brookfield is planning for the Halley Rise site. The site pre-dates the subway line, so developers were forced to build several massive parking garages to accommodate people who drive to the area's shops and restaurants. That drives up the cost of a development like this while making it less appealing for people living in the area—since no one wants to live next door to a parking garage.

Self-driving shuttles could help

Optimus Ride CEO Ryan Chin argues that self-driving shuttles can play a role here.

"When the metro opens, we expect that there's gonna be some modal shifts," Chin said in a Monday interview at the Halley Rise construction site. "People that normally would have driven here because there was no other way. Now the metro opens, they can take this system."

And that works the other way, too—people who live at Halley Rise can take an Optimus Ride shuttle to the metro stop, then take the metro to their jobs downtown.

In either case, there's a big payoff for developers: they don't need to build as many parking spots. Building parking spots is expensive—especially if they're in parking garages. And developers can use the extra land to build more housing, office, and retail space. That means extra profits for Brookfield, giving Brookfield an incentive to subsidize the shuttles, making them free to riders.

And that, in turn, sets up a virtuous circle: the more residents the neighborhood has, the more retail stores it can support. The more retail stores there are, the easier it is for residents to do their shopping on foot (or in Optimus Ride shuttles) and the less reliant they are on their cars. So driverless shuttles could make it much easier to create islands of car-free urbanism in a sea of suburban sprawl.

Obviously, shuttles like this aren't a new concept. Airports have had them for decades. But self-driving technology could make them both cheaper and better. With no driver and an efficient all-electric design, these shuttles will be cheap to operate. Having no driver also means it's viable for each shuttle to be much smaller—Optimus Ride's shuttles have room for four to six people—and to have a larger number of shuttles instead. That should reduce the waiting time to near zero, since there can almost always be a shuttle waiting for people.

In the long run, this could work on a much larger scale than Brookfield's current 36-acre site. Optimus Ride shuttles could make it feasible for people a mile or two from the subway stop to commute to work without a car. Optimus Ride could eventually sign deals with other real estate developers in the area to use the shuttle service, expanding the range of people who can get to the Silver Line—as well as the shops and restaurants at Halley Rise—without a car. People who live in Halley Rise could take a free shuttle to Reston Town Center, and vice versa.

And Optimus Ride is hoping Halley Rise will be a model for other similar developments around the country. Chin says Brookfield operates dozens of large sites like Halley Rise. Optimus Ride hopes that success here will lay the groundwork for deployments like it across America and around the world.

Optimus Ride hopes to begin driverless operation in 2020

To be sure, none of this has happened yet. Brookfield is still in the early stages of developing the property. The subway station is expected to begin operations next year, and the development's anchor Wegmans grocery store isn't scheduled to open until 2022.

Most importantly, Optimus Ride hasn't demonstrated a capability to operate its vehicles with no one in the driver's seat. Right now, the company still has two people in every vehicle—a safety driver behind the wheel and a second employee monitoring the vehicle's behavior from the passenger seat.

Chin told me that the company hopes to begin commercial driverless operations next year. This, of course, is a promise we've heard before. Google's self-driving company, Waymo, was planning to launch a driverless commercial service last year but failed to do so. GM's Cruise scrapped its own plans for a 2019 driverless launch earlier this year.

But there are some reasons to think a small company like Optimus Ride might succeed where its larger rivals so far have not. Waymo is trying to build a service that will operate in more than 100 square miles, including at freeway speeds. Cruise is trying to master the complex driving dynamics of downtown San Francisco. In contrast, Optimus Ride is only trying to master the 36-acre Halley Rise site, and initially, the cars won't go faster than 20 miles per hour (32km/h).

Self-driving at 20mph is a much easier problem than self-driving at 60mph (96km/h). If anything goes wrong, a vehicle doing 20mph can safely slam on the brakes. Optimus Ride can also work with Brookfield to make sure the roads are as friendly as possible for autonomous vehicles, with clearly marked lanes and no weird intersections.

But even this simplified version of the self-driving problem might prove too difficult to solve in the next year. We'll have to wait and see.