Highway safety advocates are urging lawmakers to pump the brakes on the development of driverless cars.

The sound — and smell — of thousands of idling trucks at the ports of Los Angeles and Long Beach could be fading if a new pilot project to convert them to part-time electric vehicles sticks.

The idea of highways being filled with self-driving cars may be alluring, but it has highway safety experts raising numerous questions about common contemporary issues like drunk driving, seat belt use and how other motorists might react to a car without a driver behind the wheel.

State and regional transportation officials largely praised the vote by the U.S. House of Representatives to ease the development of self-driving cars, and the technology associated with them, Sept. 6.

Workers in the trucking and other industries that move people and goods could find themselves squeezed out of those jobs by the rise of self-driving trucks.

It could be years before drivers on U.S. highways catch a glimpse of a tractor-trailer rig cruising down the highway with another truck trailing a perilous 20 or 30 feet behind.