Major automakers and the U.S. government have reached an agreement to make automatic emergency braking standard equipment on most cars by 2022, two people briefed on the deal said.

The agreement will be announced Thursday by 20 automakers and the National Highway Traffic Safety Administration. Automakers will phase in the equipment on nearly all models except some with older electronic capabilities and some with manual transmissions, said the people, who spoke on condition of anonymity because terms of the agreement haven't been announced.

Automatic emergency braking uses cameras, radar and other sensors to see objects in the way and slow or stop a vehicle if the driver doesn't react. The technology already is available as an option on many models, but automakers are struggling with how to fit it into current product plans that might not be ready for the electronics. Making the feature standard equipment on nearly all cars will speed adoption of the technology.

NHTSA chief Mark Rosekind wouldn't comment on the announcement at an autonomous car conference Wednesday in Dearborn, Michigan, but he indicated that the agreement would cover tractor-trailer rigs as well as cars and other light vehicles.

"Safety should be universal," he said. "For us it's all vehicles on the road."

Cars with automatic braking can cut rear-end crashes by about 40 percent, eliminating about 700,000 police-reported crashes per year based on 2013 data, according to a study released in January by the Insurance Institute for Highway Safety. That number represents 13 percent of all crashes, according to the study.

The automatic braking systems are the biggest safety advancement since electronic stability control, said Jake Fisher, auto testing chief for Consumer Reports magazine. The systems bring life-saving features of autonomous cars to the public, he said.

"It's the first time we're seeing a system that will see a problem and react for you," Fisher said. "That's kind of a new frontier, I think, in automotive safety."

In September, 10 automakers committed to the government and a private safety group that they will include automatic emergency braking in all new cars, but the announcement didn't specify a timetable for making the change.

Safety advocates were swift to criticize the effort as a backroom deal that allows automakers to avoid the possibility that the Transportation Department will impose a legal requirement for inclusion of the braking systems in cars and set binding standards for the technology.

Transportation Secretary Anthony Foxx has said such agreements will speed up crash-prevention technology instead of having to wait years for it to go through the government's cumbersome rule-making process.

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