We've heard a lot about the projected benefits of driverless cars (whenever we get them, that is). The roads will become safer, as we remove distracted, flawed drivers (and human error) from behind the wheel. Congestion will decrease, as cars that drive themselves and communicate with each other are able to more efficiently share roadways. Fuel economy will go up as a result, and emissions will go down. We'll need to devote less space to parking, as automated vehicles come to function more like public transit, remaining perpetually in motion. And all kinds of people who can't currently drive – the young and old, as well as the disabled – will become more mobile.
Which is all well and good. But exactly how many fewer crashes are we talking? How much money and gas and time would we save? Can we get some numbers, please?
The Eno Center for Transportation this week released a helpful paper that corrals many of these estimates. The benefits of autonomous cars will expand as there are more of them on the road. Ten driverless cars on the 405 in Los Angeles, for instance, won't do much to improve congestion for everyone around them. But if 10 percent of vehicles on the highway were autonomous – with the capacity to communicate with each other – that might start to change things.
Below, Eno has estimated several impacts of AVs in a graduated future in the United States where 10 percent, then 50 percent, then 90 percent the market shares this capability:
Currently, the United States has about 5.5 million vehicle crashes a year, about 32,000 of them fatal. And transportation researchers believe that about 93 percent of those crashes are caused by human error. Remove that element from the roadway, and we might approach a future where the fatality rates on roadways come to look a lot more like they do with airplane and rail travel. (Random fact: the only crash that Google has so far reported from its AV experiments occurred after a human driver took over for the computer.)
The right column above is pretty far into the future. But with 10 percent penetration, we're still talking about 200,000 fewer crashes, 100 million gallons of gas saved, and $37 billion in economic savings. Eno estimates that all drivers will experience congestion savings early on, whether you're in an automated vehicle or not. Crash benefits, on the other hand, will go primarily to the people riding in AVs. So those numbers will rack up more over time. The report also projects that the total number of vehicles on the road will decline, as the average number of miles driven per vehicle goes up.
Eno acknowledge that its analysis is "inherently imprecise," and of course a whole lot of obstacles – of the technical, legal and cultural varieties – need to be overcome before we even get to a 1 percent market share. But it's helpful to see some numbers in the meantime.
For the curious, these are the assumptions baked into the above data:
Top image taken from the back seat of a driverless car at Volkswagen Automotive Innovation Laboratory at Stanford University: Kevin Bartram/Reuters.