Ghost in Musk's machines: Software bugs' autonomous joy ride
Getting serious before things get serious for self-driving vehicles
Last year, a dark historical landmark was reached. Joshua Brown became the first confirmed person to die in a crash where the car was, at least in part, driving itself. On a Florida highway, his Tesla Model S ploughed underneath a white truck trailer that was straddling the road, devastating the top half of the car.
Brown’s crash is well known. But more mundane bugs are finding their way into increasingly software-dependent, semi-autonomous cars. Software problems accounted for nearly 15 per cent of US car recalls in 2015, up from less than five per cent in 2011, according to the most recent report from financial advisors Stout Risius Ross.
Last year, to name a few examples, Toyota recalled around 320,000 cars after they found “improper programming” could cause airbags and seatbelt pretensioners to activate unbidden. Ford had to recall 23,000 cars because software problems in their electronic windows meant they had excessive “closing force.”
Despite the latest wave of excitement about artificial intelligence, the fear among some of those in the industry is that bugs could prove a serious hurdle to mass adoption – not least because of the weird, unexpected nature of the accidents they can cause.
Philip Koopman, an associate professor at Carnegie Mellon University and an expert on autonomous vehicle safety, told The Reg: “I look at the errors, and almost always say: ‘Wow, that should not have happened.’ And the most likely explanation is that they did not follow a safety standard.”
The “continuous stream” of defects in the car industry signals “underlying problems: they just don’t want to spend the time and effort to get it right,” he argues.
Car manufacturers contacted by The Reg were unwilling to talk.
Significantly, many developing autonomous vehicles are hiring developers from Silicon Valley whose backgrounds are in general purpose software – software that, of course, crashes with reasonable frequency. People are not hiring from among the ranks of the airline safety industry.
“Knowing how to code is not knowing how to be safe,” Koopman says.
Allegations of poor code go back years. Koopman was an expert witness for plaintiffs in a 2013 court case in Oklahoma that looked into whether computer problems had caused a Toyota Camry to accelerate uncontrollably and crash, killing a passenger in 2007.
He and another investigator found Toyota’s electronic throttle control system was “just awful.” An 18‑month investigation found numerous problems in the software [PDF], including the potential for stack overflow and no protection against bit flips – where ambient radiation in the outside environment can switch a bit. The report concluded Toyota’s code was “spaghetti.”
The jury decided the electronics had been at fault and awarded $3m in compensation. Toyota stands by the safety of its throttle system, a company spokesman said, pointing out that an earlier official investigation, partly carried out by NASA, did not find any faults.
Yoav Hollander, founder of Foretellix, a company looking to develop new ways to find bugs in engineered systems, has for a number of years been attending conferences about verifying the safety of autonomous cars (and other autonomous systems). He was not impressed by progress initially, although thinks the situation is now “improving.”
One of the issues, Hollander says, is that companies are overly focused on preventing what he calls “expected bugs” – where engineers anticipate a problem. This might include making sure that the car cameras can correctly identify a pedestrian wearing a black coat at night.
But then there are unexpected bugs – problems that no one has thought of or situations that have been overlooked. A car designed in the US but driven in the UK could set off on the right hand side of the road simply because its default location is the US – all because a developer forgot to include an instruction to check location after a memory reset.
These kinds of “autonomous vehicle only” bugs – mistakes that no human would ever make – will be big news, Hollander says. “People will say: ‘Hey, I’m at the mercy of the vehicle’.”
The Joshua Brown crash – driving at full speed into a clearly visible trailer – is arguably one such example as it “would never happen to a human being,” Hollander says.
After the Florida accident, Tesla reportedly wasn’t immediately sure why its autopilot system hadn’t braked. They probed the possibility that the system deliberately ignored the trailer to avoid braking when approaching objects like overhead bridges. This was an idea supported by an investigation [PDF] by the National Highway Traffic Safety Administration.
A Reg request for clarification from Tesla went unanswered.