In the US being far too conservative usually means they want to run over Mexicans, poor people and anyone more liberal than Hitler, but in this case it means that they are driving like your gran, or anyone else who is terrified of breaking the rules.

One women moaned that she almost hit one of the company's minivans because it suddenly stopped while trying to make a right turn, while another man said that he gets so frustrated waiting for the cars to cross the intersection that he has illegally driven around them.

The problems show how challenging it can be for self-driving cars, which are programmed to drive conservatively, to master situations that human drivers can handle with relative ease -- like merging or finding a gap in traffic to make a turn.

Waymo has been testing its vehicles in the Phoenix suburbs for little more than a year and is widely seen as the furthest along in the self-driving car space, but its safety drivers have to take control of the vehicles regularly, people with direct knowledge of the issues tell The Information.

A Waymo spokesperson said its cars are "continually learning" and that "safety remains its highest priority" during testing.

The spokesperson also said that Waymo is using feedback from its early rider programme to improve its technology, though it declined to comment specifically on the intersection complaints mentioned in The Information story. The company has previously said that it plans to launch a commercial self-driving taxi service before the end of the year, but that its service will still include a Waymo employee in each car as a "chaperone".