Why self-driving cars will kill the T

They might seem like science fiction, but they’ll be here before the Green Line Extension, and they’ll be way more efficient for commuters.

Photographs from associated press; globe staff photo illustration

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Imagine for a moment it’s 1905. Boston’s growth has sent demand for horses and buggies soaring. So city leaders hatch an ambitious plan: Raze several neighborhoods and replace them with badly needed stables. Establish a fleet of cleaning crews to sweep manure from the streets. Develop a municipal program to boost the number of horses so that even the poorest of residents can have access.

Ten years later, everyone involved looks silly. The horseless carriage — the car — has arrived, rendering the horse and buggy almost obsolete. A lot of effort and taxpayer money have gone for naught.

We are at the cusp of such a disruptive change right now. But instead of cars replacing buggies, autonomous vehicles, or self-driving cars, will soon replace drivers. Their massive and far-reaching impact will make our current urban planning efforts look as absurd as it would have been to put stables in Southie in 1905. For instance, Boston’s city planners think that by 2030 public transit usage will climb by a third, so they want to extend the Green Line into Somerville. They’re wrong. By 2030, it’s more likely the MBTA will be going the way of the dodo.

Hear me out.

Environmentalists and planners love public transit. Those who ride it? Not so much. Trains, trolleys, and buses are crowded and inconvenient. They don’t run on your schedule, they run on theirs — sometimes, anyway. Check out the grim faces of your fellow passengers the next time you’re on the subway. And for many riders, a trip via public transit means a time-consuming series of hops — foot to bus to train to another train to bus and then back on foot. Little wonder the latest numbers from the MBTA show a 2 percent drop in train ridership and a 6 percent drop in bus ridership.

By contrast, a car is convenient. You start and end where you want. While driving, you can talk on the phone or sing as loudly (and badly) as you please. Nevertheless, we Bostonians suffer through 409 million trips on the T annually. Why? Because owning a car is expensive — almost $8,500 a year. And, of course, the congestion.

Not so with AVs.

In an October report, the Boston Consulting Group argued that autonomous vehicles’ most profound near-term impact would be in reducing congestion and pollution. AVs don’t rubberneck when passing accidents (in fact, AVs should have far fewer accidents). They’ll know when to change lanes safely in traffic, they can follow each other more closely (thereby increasing the effective capacity of highways), and they don’t experience road rage. Moreover, AVs likely won’t be individually owned; instead, there will be fleets of them available to riders on demand, akin to Uber. Once we’re dropped at our destination, our AV won’t need to find parking; it’ll simply move on to the next customer (and if there are none, it’ll find a designated lot to wait). As for pollution, it’s widely expected that AVs will be electric or at minimum hybrid.

Consider that if AVs no longer need to park, an additional lane or two now given over to street-side parking could be available for travel, opening up roads.

On top of that — and most compelling — AVs will be cheaper than public transit. Look at today’s cars. Despite that $8,000-plus annual cost, they are actually pretty cheap on a per-mile basis. Nationally, an average automobile costs $0.56 per mile to drive, says the American Automobile Association, plus another $0.02 per mile in subsidies for roads and bridges. Public transit costs almost twice that, at $1.05 per mile, according to the American Public Transportation Association. But public transit users are heavily subsidized; at the T, fares cover a scant 30 percent of expenses. Thus it appears more economical than driving, and congestion means it’s often the faster choice. Plus, the costs for cars don’t include parking — $300 to $500 a month at downtown lots.

With AVs, we’ll eliminate that parking cost, and congestion will largely disappear. And since we’ll use AVs in an Uber-like fashion, we’ll pay only when we need a ride — without the cost of a driver. Indeed, the per-mile cost of AVs should be less than conventional cars. Insurance will be cheaper (or perhaps unneeded). Electric AVs will average the equivalent of 100 miles per gallon or more, versus the 25 miles per gallon of today’s gas-powered cars. The vehicles themselves will be used more efficiently (since they won’t spend most of their days waiting for their one owner to get behind the wheel).

Given the choice between an AV and public transit, who wouldn’t choose the faster, more convenient, and lower-priced alternative? That’s the predicament the T will face. As AVs quickly gain commuters’ favor, fewer will take public transit. Fare collections will decline, requiring either higher fares — which would drive away even more riders — or more subsidies. Eventually, we’ll simply conclude that trains and trolleys are things of the past. Like the horses, buggies and stables of old, they’ll become relics.

All won’t be lost, however. We could still rip out the tracks and make some really good bike paths.