By Eric Jaffe, February 13, 2014
If connected vehicle technology becomes mandatory in American cars, as
the Department of Transportation recently suggested it might, the most
obvious benefit would be safety. Cars that can tell other cars their
speed and position are far less likely to crash. But as David Zax
pointed out at Cities earlier this week, that's just the beginning. Combine connected vehicle technology with intelligent infrastructure and driverless cars and you get a commute that's both quicker and hands-free. You could even rely on autonomous taxis to chauffeur you from home to work.
In that sense, a world without car crashes may just be the first step to a world without car-ownership.
Of course, right now cars are neither connected nor autonomous, and the
vast majority of Americans still commute to work by driving alone — a
cultural habit that will be hard to replace. But we're not so far away
from this future that it's too early to start considering what it might
look like. As Matt Yglesias wrote at Slate in August,
Google, the leaders in autonomous car technology, must have had some
vision in mind to shell out $258 million for the car-slash-ridesharing
service Uber: "ubiquitous taxis — summoned via smartphone or weird
glasses — that are so cheap they make car ownership obsolete."
Think about this world of shared autonomous vehicles for a moment. You
wake up and get ready for work, and a few minutes before it's time to
leave you press a button and order an SAV. The car has been
strategically positioned to wait in high-demand areas, so you don't have
to wait long. You might share the ride with a couple travelers just as
you share an elevator, or perhaps pay a premium to ride alone. Either
way, you clear your inbox or read the paper during the commute, which is
safer and more reliable than it used to be.
"It's a game-changer," says autonomous car researcher Alain L. Kornhauser
of Princeton University. "What I think is going to happen is that
nobody will own a car. … If you can get [mobility] by the drink, you
won't buy the bottle."
The problem with buying the drink today, says Kornhauser, is that the
labor cost of on-demand taxi service is enormous. As a result, we buy
the bottle just in case we want a drink. Driverless cars change the
whole equation. Right now less than 17 percent
of U.S. household vehicles are in use at a time. If even a fraction of
those unused cars were replaced by SAVs, the car-ownership reduction
could be huge. Especially when you consider that a quarter of car-share members already give up their cars — with another quarter opting not to buy one.
Civil engineer Kara M. Kockelman of the University of Texas at Austin recently modeled
the potential ownership change with grad student Daniel Fagnant. Using
Austin's density and population as their baseline, they simulated an
average weekday of travel in a 10-by-10 mile zone of the city. They made
the conservative assumption that only 5 percent of all trips would made
by shared autonomous vehicles. The rest would drive their own cars as
The results offer an enticing glimpse of a world without car-ownership.
Each SAV in the Austin model replaced about 11 conventional household
vehicles. The roughly 20,000 people who made up this shared network,
formerly owners of roughly as many cars, were now served by a mere 1,700
SAVs. Travelers waited an average of only 20 seconds for their ride to
arrive, and you could literally count the number who waited more than 10
minutes on one hand (three). That's to say nothing of personal savings in terms of cost (insurance, parking, gas) and time.
"Even when we doubled or quadrupled or halved or quartered that
trip-making, we didn't have big changes in our key variables," says
Kockelman. "This replacement rate, this eleven-to-one, those things were
Kockelman is quick to point out the caveats. The biggest is that for
all the savings in private car-ownership, vehicle-miles traveled doesn't
go down in the Austin model. In fact, it goes up about 10 percent.
That's because not only are SAVs making all the trips people used to
make on their own, but they're repositioning themselves in between trips
to reduce wait times (see below). The additional wear also means
manufacturers produce about the same number of cars, too, though each
new fleet is no doubt a bit smaller and cleaner than the last.
"So total miles-traveled is not going down — it's actually going up,"
she says. "Instead of driving 100,000 over 10 years, they're driving
100,000 miles every year."
One SAV's 24-hour journey.
Skeptics have also charged that autonomous cars will disrupt any
city-based travel models, since people freed from the need to drive will
move even farther away from the core. That might be true for
people who own their autonomous cars, says University of Minnesota
transport scholar David Levinson,
but a strong sharing system could promote the opposite movement. "If
you're paying for the car by the minute, then you're not going to want
to move farther out," says Levinson. "You're going to want to move
Levinson says SAV service that offers convenient on-demand trips gives
people a much greater incentive to rely on that system — and a much
smaller incentive to take the unnecessary trips often made by private
cars. It's a recipe for the type of multi-modal lifestyle change only
possible right now in places like Manhattan. Transit for essential daily
trips, cabs (or other alternatives based on the type of trip) for the
That raises perhaps the biggest question for cities to ponder between
today and a shared autonomous tomorrow: Could an SAV network perpetuate
car travel so much that it eliminates public transportation?
For sure, it means a greater reliance on roads and automobiles. But
Kornhauser points out that an SAV network also has the potential to
enhance transit ridership on existing commuter routes. After all, a
convenient ride to and from the station could increase demand enough for
transit agencies to run even more trains or buses.
"Because there's such an increased demand in train service, instead of
having service every half hour or hour, you have service every 10
minutes, every 5 minutes," he says. "It's a whole new ballgame."
At the same time, SAVs might even represent an upgrade to existing
transit service in many low-demand corridors. A few SAVs perched outside
such neighborhoods might provide the area more cost-efficient and
reliable service than a few buses running every half hour or hour. That
doesn't solve the problems of funding low-demand transit corridors, but
it does reduce the scale of the investment — and it also makes
door-to-door trips easier for aging and disabled populations.
The worlds of transit and car-share are already starting to converge. In Portland, Zipcar recently partnered
with TriMet, the city's transit agency, to offer riders a new option
for the first-and-last mile of their commute. That's a sign the demand
for a mobility network free of car ownership is growing even without a
driverless element. Cities that fail to start asking questions a shared
autonomous future now risk making transport investments that could
become irrelevant even before they're completed.
The big market question is when this world will begin to emerge.
Levinson subscribes to a timeline in which autonomous cars enter the
luxury market in 2020, the technology trickles down into the affordable
mid-level range over the next several years, and by 2030 every car on
the road is driverless. (Other cars would be banned a decade later.)
Since car- and ride-sharing operations tend to rely on smaller cars,
that would peg SAV networks closer to 2030 — about 16 years from now.
"It's not that far away anymore," says Levinson. "But 16 years ago was
1998, and Google hadn't been invented. So it's a short time and it's a