Nailing down the safety benefits of robocar technology is harder than it looks. Of course, any system that keeps you from driving into a brick wall must be good for your health, but the problem is that not all drivers handle such safety features properly.
Three recent studies all have to do with this critical interaction between technology and people. The first one, published in the most recent issue of IET Intelligent Transport Systems, shows that if every car came with both an emergency braking system and a pedestrian and cyclist detection system, it would cut by 7.5 percent the total number of traffic deaths among these “vulnerable road users.” That decrease, say the authors of the study (who hail from Finland, the Netherlands, Austria, and Britain), “comes down to an estimate of around 1,900 fatalities saved per year” in the European Union.
That safety system combination yielded the best result of the 10 driver-assistance technologies the authors considered. But even so, it falls a percentage point or two below what you’d get if pedestrians and cyclists were unaware that the cars had the two safety features. It’s that comforting knowledge that a car can make up for their carelessness that tempts pedestrians to cross in front of such a car when they shouldn’t.
Safety engineers call such trading of safety for convenience risk compensation. They’ve been struggling against it for decades.
I was in Detroit back in the 1980s when Mercedes Benz came to demonstrate its new antilock braking system (ABS) by driving a car over a half-soaped stretch of asphalt, with the left-hand wheels on the soapy side and the right-hand wheels on the dry side. When the driver stamped on the brake, the car stopped easily, without the slightest swerve or skid.
“When this comes out on a car I can afford, I’m buying it with my own money,” my newspaper bureau chief told me. “I’m not waiting for the safety guys to make it mandatory.”
Customers did pay willingly for ABS, in part because they were encouraged by auto insurers that offered discounts. The insurance companies then sat back and waited for the accident rate to fall. But it didn’t. The ABS instead encouraged drivers to tailgate a little more and take curves a little faster.
Still, if you really load a car up with safety tech, you can swamp the human proclivity to act like an idiot. The car will save us from ourselves, despite our own best efforts to hinder it.
Take electronic stability control (ESC), the next-gen elaboration of ABS. As its inventor, Anton van Zanten, told IEEE Spectrum last year, “ABS works only during panic braking, not during coasting or partial braking or free rolling, and traction control usually works only if you have full acceleration. But ESC controls car motion at any time.”
ESC is the subject of another paper that appears in the same issue of the journal. Unlike most such analyses, this study, from Finland, doesn’t model future scenarios in which all cars carry ESC. It just estimates how many lives the technology actually saved in 2014. The conclusion: Thirty-seven lives were saved, equal to 16 percent of all road traffic deaths that year; and 747 injuries were prevented, equal to 11 percent of traffic injuries.
The third study, from researchers at the University of Illinois at Urbana-Champaign, concerns not safety but the efficient flow of traffic. Here, too, the point was to confirm, with hard evidence, something experts had long expected: that a self-driving car can head off the formation of so-called phantom traffic jams.
A phantom jam comes when human drivers tap the brake to add a little space between themselves and the car in front of them. Their own braking then provokes a similar, but slighly delayed, response in the driver just behind them, which has the same effect on the next driver down the line. The resulting “traffic wave” strengthens as it propagates backward until at last it produces a jam.
“Our experiments on a circular track with more than 20 vehicles show that traffic waves emerge consistently, and that they can be dampened by controlling the velocity of a single vehicle in the flow,” say the authors. “These experimental findings suggest a paradigm shift in traffic management: Flow control will be possible via a few mobile actuators (less than 5 percent) long before a majority of vehicles have autonomous capabilities.”
It’s a kinder, gentler version of a trick that state troopers used in the 1970s and 1980s, when motorists routinely flouted the national speed limit of 55 miles per hour. Two patrol cars would drive side by side to create a “rolling roadblock.” Here, though, the robocar isn’t forcing anyone to do anything—it’s just proceeding at a steady pace, braking precisely when it must.
Philip E. Ross is a senior editor at IEEE Spectrum. His interests include transportation, energy storage, AI, and the economic aspects of technology. He has a master's degree in international affairs from Columbia University and another, in journalism, from the University of Michigan.