DETROIT – Federal safety regulators launched a streamlining of U.S. auto safety ratings Monday into one score on a five-star scale, with an extra credit to automakers that put more advanced safety technology in their vehicles.

With most car models getting the top four and five ratings on many crash and rollover tests, the scores have lost much of their impact, federal regulators fear.

The U.S. Department of Transportation Secretary Mary Peters said officials were seeking ways to improve the government’s new car assessment program. In addition to revised scores, regulators said they would take more measurements in front and side crash tests, among other changes. Federal regulators will seek public input on implementing the changes.

The proposals “are common sense in their approach and comprehensive in their scope,” Peters said. “Without question, and without government mandate, automakers realize safety helps sell cars, and more and more cars receive the highest ratings.”

While auto executives welcomed the proposals, safety advocates said they would have little effect on the 43,000 deaths on roads annually, a statistic that has changed little despite years of safety efforts.

“Vehicles are much better at protecting passengers, but we are still losing a lot of people,” said Adrian Lund, president of the Insurance Institute for Highway Safety. “My concern is it doesn’t go as far as we’d like.”

Government regulators hand out five different star ratings today – front driver and passenger, side driver and passenger and rollover prevention. For the crash tests, the stars indicate the likelihood that someone in such a crash would be injured. A five-star rating in a front crash test means someone in a crash has a 10 percent or lower chance of being seriously injured, with 5 stars equal to a 5 percent risk in side impact tests.

The rollover tests measure the likelihood that your car or truck would roll over if it crashed; vehicles with one star are four times more likely to roll than vehicles with five stars.

A few years ago, a five-star rating was enough of a selling point that automakers advertised the good scores. The problem for the National Highway Traffic Safety Administration has been that as automakers have made their vehicles more crashworthy, low star ratings have become increasingly rare. Few vehicles get less than four stars in front crash tests, and NHTSA said 89 percent of models now get four or five stars in side impact tests.

Other groups, notably the Insurance Institute, have altered their crash tests to make them tougher. To earn a top grade from IIHS, automakers now must pass front and side crash tests, protect against whiplash injuries in rear-end accidents and offer electronic stability control.

Under NHTSA’s proposal, the agency would combine all front and side crash tests into a single rating. It said it would research ways to combine the rollover ranking as well as adding points for vehicles sold with advanced technology, such as lane departure warning systems, into a single score.

NHTSA also would adopt a variety of smaller changes, such as measuring injuries to legs and knees in head-on crashes, perhaps with a new test run at lower speeds than the current tests.

Bob Lange, General Motors Corp.’s executive director of vehicle safety, said he welcomed Peters’ proposal.

“We would like to see some credit given for the application of advanced technology,” he said.

Public Citizen, a safety advocacy group, faulted NHTSA in a statement for not proposing new tests aimed at reducing rollover injuries or pedestrian accidents, and had no way to compare how well small vehicles survive in crashes with much larger ones.

Lund said the IIHS also had struggled with some of the same issues NHTSA was facing, but believed there was far more work to be done in designing stricter tests.