WASHINGTON - Federal safety regulators issued a rule that requires improved side-impact protection in new cars and trucks, starting with the 2010 model-year.

For the first time, test vehicles will be slammed sideways into a pole to determine how well they protect occupants.

The government does not normally mandate specific vehicle safety technologies. But experts predict the new rule will require most new vehicles to have side-impact airbags that provide head protection - a potential boon to suppliers of airbag curtains and similar devices.

The Alliance of Automobile Manufacturers said in a statement that its member companies are working to meet a voluntary commitment they made in 2003 to improve side-impact protection. The alliance said 84 percent of 2006-model vehicles had head-protecting side-impact airbags.

The National Highway Traffic Safety Administration (NHTSA) issued the final side-impact rule more than three years after the agency announced its intention to adopt the tougher standard. In 2005, Congress mandated that the rule-making be completed.

Transportation Secretary Mary Peters said the new standard, when it is fully applied across the vehicle fleet, will save hundreds of lives a year and will prevent hundreds of serious injuries.

For most vehicles, the new requirements are to be phased in by Sept. 1, 2012. The deadline is Sept. 1, 2013, for vehicles of 8,500 to 10,000 pounds gross weight, such as the largest SUVs. NHTSA said the new rule also upgrades the existing side-impact crash test and requires the use of advanced crash dummies, one of them the size of a small female.