What do driverless cars mean for suburban planning?

Self-driving cars are coming, and boosters of drivable suburbia are hoping they will be a potent weapon against mass transit and cities. But what they mean for towns and suburbs isn’t quite so clear.

For the past 80 years, the US has transformed nearly every place in the country into one that is acceptable and welcoming to the personal automobile. It needs places to park (some estimates have that there are 6 parking spaces for every car), needs enough road space to be able to drive unimpeded, needs sole control over the roads, and so on.

In places built in the past 30 years, this has meant sidewalk-free eight-lane boulevards and massive malls at freeway interchanges. In places built before the car, this has often meant their wholesale destruction. (Santa Clara and Fremont, for example, are now undertaking efforts to “rebuild” their town centers.)

This has not been in service to the car as a vehicle, however, but to the car as a personal mobility tool. Very often, the only seat used in a car is the driver’s, massively enhancing the person’s footprint and leading to all kinds of horrific traffic.

With the advent of the driverless car, the belief is that we will no longer need personal vehicles, and this excess footprint will become unnecessary. Open up an app on a phone, order a car, and a vehicle (possibly with others in it going to roughly where you’re going) will drive by, pick you up, and drop you off near your destination. Along the way it’ll pick up other people going in roughly the same direction as you, bolstering capacity of the personal car to a grand total of five.

Five trips, one car. As one Twitter follower called it, it becomes mini-mass transit, but at the beck and call of an app and as flexible as it needs to be. If this method of travel becomes ubiquitous – and that’s a big if – then the personal automobile might become a thing of the past.

What, then, of the places we’ve outfitted at great expense to fit the personal automobile? These would need to be retrofitted to fit this new dominant mode, and we can do away with some of design choices that favored the personal automobile.

Probably the biggest change is the demise of the large parking lot. These huge slabs of asphalt dominate suburban commercial landscapes, often taking up 80 percent of commercial parcels. They dominate the streetscape, and arterial suburban roads are lined with them. Without personal vehicles to park, there’s no need for a parking lot. That land could be put to productive use.

All this will be wasted space.

With a transportation system that’s five times as efficient, too, there’s little need for wide arterial roads packed with single-occupant vehicles. As well, without human drivers, there’s no need for “forgiving engineering” focused on driver psychology and driver needs. We can narrow lanes from 12 feet (freeway width) down to 10 feet or even 9.5 feet and have the same vehicle capacity and speed. There would rarely be a need for roads wider than 2 lanes in the suburbs.

So, we can wave goodbye to parking lots and wide arterial roads. What could we do to optimize the suburbs to fit this new reality?

First, trip origins and destinations would be best served if they are along the same axis of travel, and they should be relatively evenly spaced and close together. Street grids lined with origins and destinations make sense, so as to maximize the directness of the travel. That means either a commercial street with homes behind or above.

With the loss of parking lots, it makes no sense to place storefronts far back from the street. They should be placed against the street to ease access for passengers.

Finally, there will likely be a need for a short walk to or from a vehicle, especially when returning home. It makes sense to make that walk a pleasant one, and to put amenities there, too.

Relative capacities of modes

It’s important our density not get too high. Although boosting car capacity fivefold is a huge step forward, trains have eight to forty times the capacity. For the highest-density areas, where trains are already at capacity, driverless mini-mass transit won’t be enough to solve congestion or to adequately meet residents’ travel needs.

So in the retrofitted suburbs, there should be a balance between the need for a dense line of origins and destinations and the need to not overload the system. Perhaps just six stories, at most, in the most dense places of the suburbs.

For this kind of system to work and not devolve into that kind of nightmare, it needs to have simple and easy lines of operations, just like the streetcars did, with origins and destinations located near stops. Unlike streetcars, the whole street is a possible stop. Rather than a series of one-dimensional stops surrounded by a station area, there is a two-dimensional transportation corridor surrounded by a transportation area. The station neighborhoods currently in existence could easily be integrated into suburban corridor fabric.

At this point, this does not sound much like the suburbia we often consider “suburbia”. With no parking lots, no wide roads, a street grid, and shops and homes clustered up against the sidewalk, it sounds more like a town center. That’s because this transportation cloud functions much more like the streetcars of the old days than personal cars of today. The urban landscape described is precisely the kind of bus-transit-oriented development that suburbs could be investing in today. This article could have painted just the picture: “Imagine standing at almost any street corner, where every five minutes an electric train bus vehicle comes by…”

Indeed, if this system ever does overcome myriad regulatory hurdles, it will work best in places where buses and light rail work best. If this is our dream future, then we can start planning for it today. There’s no need to wait for driverless cars.*

Of course, this system will likely be decades away, if it ever happens. There are huge regulatory hurdles to any driverless car, and any area where this system operates could be seriously disrupted by even one person driving their own car. As well, there are still questions of who owns and maintains the vehicles. In the interim, personally owned automated vehicles will likely start to ply the roads. (While they will reform how we use parking, they won’t do much about traffic.)

But if this system does come, it’s not something for champions of small towns, walkable living, and transit to fear.

*As people start to buy personal driverless cars, the need for vast parking lots will diminish. If we really want to start planning for that reality, too, then we should reform or abolish parking standards today. 

AN ASIDE: This system has been speculated upon for decades as Personal Rapid Transit, or PRT, though generally it was theorized on rails. In fact, it already exists, in a sense, in Morgantown, West Virginia.

Much of the time, Morgantown’s system works like an elevator (push a button to summon a vehicle, push a destination button and you’re on your way). During rush hour, it operates like standard-issue fixed-route transit during peak hours, and in off-hours each car runs the whole track as a circulator.