California Gov. Gavin Newsom has vetoed a bill to require human drivers on board self-driving trucks, a measure that union leaders and truck drivers said would save hundreds of thousands of jobs in the state.

The legislation vetoed Friday night would have banned self-driving trucks weighing more than 10,000 pounds (4,536 kilograms) — ranging from UPS delivery vans to massive big rigs — from operating on public roads unless a human driver is on board.

Lorena Gonzalez Fletcher, head of the California Labor Federation, said driverless trucks are dangerous and called Newsom’s veto shocking. She estimates that removing drivers would cost a quarter million jobs in the state.