A self-driving car from Google has been pulled over by police in California after it was being very cautious and driving too slowly, with a long line of traffic following behind.
No action was taken, but the event has prompted some to question whether autonomous vehicles are over-cautious.
Google's autonomous cars are designed to follow the rules of the road absolutely, even if human road users may not always do so, which can lead to certain challenges. Google plan to program their cars to drive more like humans, in a bid to help them fit in better on the roads.
The Mountain View police department stated that an officer "noticed traffic backing up behind a slow-moving car in the eastbound lane", as the vehicle was travelling at 24 mph in a 35 mph area.
Google commented: "We've capped the speed of our prototype vehicles at 25 mph for safety reasons. We want them to feel friendly and approachable, rather than zooming scarily through neighbourhood streets."
They also joked: "Bet humans don't get pulled over for that too often."
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