A driverless shuttle bus that was meant to transport visitors around Las Vegas, got into an accident less than two hours after it was launched. Officials had earlier held a ceremony to unveil the vehicle, thought to be the first of its kind in the country.

The City of Las Vegas said in a Tumblr post that the accident was just a graze by a delivery truck which occured while the vehicle was "testing".

"The shuttle did what it was supposed to do," the post said, "in that it's sensors registered the truck and the shuttle stopped to avoid the accident."

"Unfortunately the delivery truck did not stop and grazed the front fender of the shuttle. Had the truck had the same sensing equipment that the shuttle has the accident would have been avoided."

The shuttle will not be in service for the rest of Wednesday (8 November) and the post said that the driver had been cited. "Testing of the shuttle will continue during the 12-month pilot in the downtown Innovation District," the city said.

The pilot project is sponsored by AAA in partnership with Keolis. The shuttle covers a 0.6 mile loop, according to officials, adding that it is all-electric. The shuttle itself can transport up to eight passengers and has an attendant.

"Safety features include the ability to automatically and immediately brake in the event of a pedestrian crossing in the path of the vehicle," the city said. "The shuttle is the country's first autonomous shuttle to be fully integrated with "smart-city" infrastructure, communicating with traffic signals to improve safety and traffic flow."

The City of Las Vegas twitter account had earlier tweeted pictures of celebrities and the mayor at the shuttle's launch, later adding that people could "[b]oard the free shuttle at any of the three stops on Fremont Street and Carson Street between Las Vegas Boulevard and 8th Street."