Google reveals self-driving car slip-ups

Google on Tuesday said that while its self-driving cars have safely driven more than a million miles, there have been times when humans have had to take over to avoid crashing.

System "anomalies" caused drivers to take the wheel 272 times in California test cars in the 14 months leading up to December, Google said in a report to the California Department of Motor Vehicles.

The test period saw cars travel more than 420,000 miles (676,000 kilometers) across the state.

There were an additional 69 occasions when drivers seized control from automated systems based on their own judgment calls, according to the report.

The most common cause for intervention occurred when technology did not properly sense a real-world situation, the report indicated.