Learning how to share the road
The toughest challenge for tomorrow’s self-driving cars? Human drivers
DETROIT — In just a few years, well-mannered self-driving robotaxis will share the roads with reckless, law-breaking human drivers. The prospect is causing migraines for the people developing the robo-taxis.
A self-driving car would be programmed to drive at the speed limit, but humans routinely exceed it by 10 to 15 miles per hour. Selfdriving cars wouldn’t dare cross a double yellow line; humans do it all the time. And then there are those odd local traffic customs.
In Los Angeles and other places, for instance, there’s the “California Stop,” where drivers roll through stop signs if no traffic is crossing. In southwestern Pennsylvania, courteous drivers practise the “Pittsburgh Left,” where it’s customary to let one oncoming car turn left in front of them when a traffic light turns green. The same thing happens in Boston.
“There’s an endless list of these cases where we as humans know the context, we know when to bend the rules and when to break the rules,” said Raj Rajkumar, a computer engineering professor at Carnegie Mellon University who leads the school’s autonomous car research.
Although autonomous cars are likely to carry passengers or cargo in limited areas during the next three to five years, experts say it will take many years before robotaxis can coexist with human-piloted vehicles on most side streets, boulevards and freeways.
That’s because programmers have to figure out human behaviour and local traffic idiosyncrasies. And teaching a car to use that knowledge will require massive amounts of data and big computing power that is prohibitively expensive at the moment.
“Driverless cars are very rulebased, and they don’t understand social graces,” said Missy Cummings, director of Duke University’s humans and autonomy lab.
Driving customs and road conditions are dramatically different across the globe, with narrow, congested lanes in European cities, and anarchy in Beijing’s giant traffic jams. In India’s capital, New Delhi, luxury cars share poorly marked and congested lanes with bicycles, scooters, trucks, and even an occasional cow or elephant.
Then there is the problem of aggressive humans who make dangerous moves such as cutting cars off on freeways or turning left in front of oncoming traffic. In India, for example, even when lanes are marked, drivers swing from lane to lane without hesitation.
“It’s hard to program in human stupidity or someone who really tries to game the technology,” says John Hanson, spokesperson for Toyota’s autonomous car unit.
Kathy Winter, vice-president of automated driving solutions for Intel, is optimistic that the cars will be able to see and think like humans before 2030.
Cars with sensors for driver-assist systems are gathering data about road signs, lane lines and human driver behaviour. Winter hopes companies developing autonomous systems and cars will contribute this information to a giant database.
Someday autonomous cars will have common sense programmed in so they will cross a double-yellow line when warranted or to speed up and find a gap to enter a freeway. Carnegie Mellon has taught its cars to handle the “Pittsburgh Left” by waiting a full second or longer for an intersection to clear before proceeding at a green light.
A self-driving Uber car stops at a red light on Liberty Avenue in Pittsburgh.