The vehicle - carrying “several” passengers - collided with a lorry driving at slow speed.
Nobody was injured in the incident which city officials say was the fault of the human driver of the lorry. The man was subsequently given a ticket by police.
The shuttle is the first of its kind to be used on public roads in the US.
The collision comes a day after Waymo - owned by Google's parent company Alphabet - announced it is launching a fully self-driving fleet of taxis in Phoenix, Arizona.
