Humans holding back self-driving cars

 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 robotaxis.

A self-driving car would be programmed to drive at the speed limit. Humans routinely exceed it by 16 to 24 kmph — just try entering the New Jersey Turnpike at normal speed. Self-driving cars wouldn’t dare cross a double yellow line; humans do it all the time. And then there are those odd local traffic customs to which humans quickly adapt.

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.

During rush hours near Ann Arbor, Michigan, drivers regularly cross a double-yellow line to queue up for a left-turn onto a freeway.

“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.