Autonomous vehicles may be seen as the gold-standard of transport for the future by some, but they also have the potential to cause new forms of danger.
As reported by Wired, a fire truck in San Francisco was recently responding to a fire at 4am when one such vehicle, operated by Cruise, held it up.
The fire truck had to pass a parked garbage truck in order to proceed, but the autonomous car approaching from the opposite direction stopped, blocking its path.
Any delay for an emergency vehicle could mean the difference between life and death.
The fire truck was only able to get moving again when the garbage truck driver "ran from their work" to move it, according to Wired.
Unfortunately for the fire officers the Cruise vehicle, owned by General Motors, was operating as designed.
Tiffany Testo, a spokesperson for the company, told Wired the driverless car had "correctly yielded to the oncoming fire truck".
When it did so, it automatically contacted Cruise's remote assistance workers who can manually control the vehicle remotely.
Using camera and sensor data, Cruise said the fire truck was able to move forward around 25 seconds after it encountered the autonomous vehicle, although that was likely as an impact of the garbage truck moving.
"This incident slowed San Francisco Fire Department (SFFD) response to a fire that resulted in property damage and personal injuries," a filing submitted to the California Public Utilities Commission (CPUC) said.
According to the city, the SFFD is concerned that self-autonomous vehicles are stopping too often on the roads, potentially having a "negative impact" on response times.
Cruise is just one of the self-driving car companies operating in San Francisco, with both Zoox, owned by Amazon, and Waymo, from Alphabet, also operating around the city.
However it's going one step further than the others, by applying for a permit that would allow it to launch California's first paid driverless ride-hailing service.
Currently the company is allowed to take some members of the public on autonomous drives between 10pm and 6am in certain parts of the city.
The new permit would allow it to charge for those rides, although not when it's raining or foggy.
According to the city's filing with the CPUC, there were two other worrying issues involving Cruise vehicles.
The first was when one stopped at a crosswalk and then didn't move for five minutes, blocking traffic. Police officers also stopped one because it didn't have its headlights on, despite operating overnight.
The fire truck incident is an example of an "edge case", which the Guardian's Laurie Clarke wrote about earlier this year.
"While about 80 percent of self-driving is relatively simple - making the car follow the line of the road, stick to a certain side, avoid crashing - the next 10 percent involves more difficult situations such as roundabouts and complex junctions," he wrote.
The last 10 percent is even more difficult. The fire truck is an example of that, as is a cow standing in the middle of the road that doesn't want to move.
Edge cases, according to Clarke, are rare and unusual events that occur on the road like a ball bouncing across the street followed by a running child or group of protesters waving signs.
Autonomous vehicles rely on coded rules - like 'always stop at a red light' - combined with machine learning to ensure safe driving. However, because edge cases are rare, the car doesn't learn how to respond appropriately.
Unfortunately, as the fire truck example showed, this could end up with serious consequences.
