Google officials announced on Monday that eleven of its self-driving vehicles have been involved in traffic accidents since their debut over six years ago. 

They mention that the accidents were the result of human error and not problems associated with the engineering of the vehicle themselves. 

"One of the most important things we need to understand in order to judge our cars' safety performance is 'baseline' accident activity on typical suburban streets," Google officials wrote on Medium. 

"Quite simply, because many incidents never make it into official statistics, we need to find out how often we can expect to get hit by other drivers."

Two of the eleven accidents were side-swipes, one was a collision with a car driving past a stop sign and the rest involved being rear-ended. Most of the accidents occurred in major cities, according to TIME. 

Watch a test video of the self-driving Google car below: 

The company is using Google Chauffeur as the primary software for self-driving cars.