The long-awaited federal upgrade of the 35-year-old regulation governing vehicle roof strength will save 135 lives, prevent more than 1,000 injuries and add up to $1.4 billion annually to the cost of new cars, the Transportation Department said.

Under pressure from Congress, the National Highway Traffic Safety Administration boosted new roof-strength requirements when it finalized last week its long-awaited upgrade of roof-strength requirements -- but it issued lower requirements for the heaviest vehicles and added a phase-in period.

The final regulation boosts the requirement to three times the weight for vehicles up to 6,000 pounds. Vehicles 6,000-10,000 pounds must meet a 1.5 times standard. NHTSA says 135 lives will be saved and 1,065 injuries -- up from 44 over the previously proposed upgrade.

The new regulation will add $54 per vehicle in design costs and another $15 to $62 in added fuel costs, NHTSA said.

Automakers said the new standard will require engineering and design challenges.

The Alliance of Automobile Manufacturers, the group representing Detroit's Big Three automakers, Toyota Motor Co., Daimler AG and six other automakers, said they "support NHTSA's goal of enhancing rollover safety through a comprehensive plan aimed at eliminating rollover injuries and fatalities, and enhanced roof strength is only one part of that plan."

Members of Congress from both parties said the prior proposed upgrade didn't save enough lives.

"These new standards go a long way toward reducing deaths, but safety belts are the first, most important step everyone should take to protecting themselves and their families," Transportation Secretary Ray LaHood said.

The phase-in schedule, which begins in September 2012, will be completed for all affected vehicles by the 2017 model year. NHTSA has been grappling with updating the current regulation for more than a decade.

Beginning in the 2013 model year, manufacturers must have 25 percent of their vehicles over 6,000 pounds meet the 1.5 times standard -- a requirement that jumps to 50 percent in the 2014 model year.

NHTSA said its new rule will cost $875 million to $1.4 billion and add weight to vehicles, slightly increasing fuel use.

In January 2008, it stiffened its August 2005 proposal to require a two-sided roof-strength test, which would have the effect of requiring tougher roofs.

Automakers oppose the double-sided test, saying it is unnecessary. They have also sought more time to comply, noting the expense of redesigning vehicles.

Toughening vehicle roofs is aimed at helping people survive rollover crashes, which account for more than 10,000 deaths annually, according to federal reports. Rollovers represent 3 percent of crashes, but account for one-third of all vehicle deaths.

General Motors Corp. and Ford Motor Co. essentially wrote the regulation that's been in effect since 1973 after their fleets failed NHTSA's first proposed standard in 1971.

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