The National Highway Traffic Safety Administration on Monday said it had ordered Transdev North America to immediately stop transporting schoolchildren in Florida in a driverless shuttle as the testing could be putting them at "inappropriate" risk.
The auto safety agency known as NHTSA said in an order issued late Friday that Transdev's use of its EZ10 Generation II driverless shuttle in the Babcock Ranch community in southwest Florida was "unlawful and in violation of the company's temporary importation authorization."
"Innovation must not come at the risk of public safety," said Deputy NHTSA Administrator Heidi King in a statement.
"Using a non-compliant test vehicle to transport children is irresponsible, inappropriate, and in direct violation of the terms of Transdev's approved test project."
In March, NHTSA granted Transdev permission to temporarily import the driverless shuttle for testing and demonstration purposes, but not as a school bus.
The agency said the company had agreed to halt the tests. A spokeswoman for Transdev did not respond to several requests for comment Monday.
Transdev North America is a unit of Transdev, which is controlled by France state-owned investment fund Caisse des Depots et Consignations.
The company in August issued a news release saying it would "operate school shuttle service starting this fall with an autonomous vehicle, the first in the world."
Transdev said the 12-person shuttle bus would operate from a designated pickup area with a safety attendant on board, would travel at a top speed of 8 miles per hour (13 kph), with the potential to reach speeds of 30 mph (48 kph) once additional infrastructure was completed.
There are numerous low-speed self-driving shuttles being tested in cities around the United States with many others planned.
NHTSA previously said it was moving ahead with plans to revise safety rules that bar fully self-driving cars from the roads without equipment such as steering wheels, pedals and mirrors as the agency works to advance driverless vehicles. The agency has said it opposes proposals to require 'pre-approving' self-driving technologies before they are tested.
NHTSA told Transdev that failure to take appropriate action could result in fines, the voiding of the temporary importation authorization or the exportation of the vehicle.
Earlier this month, French utility Veolia agreed to sell its 30 percent stake in Transdev to Germany's Rethmann Group.