Car safety is one of the top factors many people consider when purchasing a new or used car. While car safety features abound in today’s cars, only two are worth spending the extra money it takes to buy a car that is equipped with them.

The first car safety feature to look for in any car is electronic stability control. It’s a system of sensors that constantly monitors the car’s response to the driver’s steering actions and then applies the brakes and reduces engine power to get the car under control during a sudden swerve or skidding.

No other car safety feature, with the exception of an occupant wearing a seat belt properly, is more effective in preventing fatalities, according to studies by the National Highway Traffic Safety Administration, or NHTSA, and the Insurance Institute for Highway Safety, or IIHS. It is very effective at preventing rollover collisions, which have the highest incidence of fatality, reducing the risk of fatal, single-car rollovers by 72 percent to 75 percent, depending on the type of vehicle involved.

Currently, electronic stability control is offered on 90 percent of all cars and by 2012, it will be required as standard equipment on all cars, SUVs and pickups. However, for used car shoppers, getting a car with electronic stability control can be a bit more of a challenge. Though it’s been available since 1995, it’s only been since the 2006 model year that it’s been on more than 50 percent of vehicles.

When shopping for a car with this safety feature, look for a system that uses the phrase “stability control” in it, as different automakers use various names for the system. Take care not to confuse this feature with traction control — a feature that prevents the wheels from spinning but has not been proven to reduce the risk of a crash.

Side air bags, which provide head or torso protection in a side-impact or rollover collision, are another car safety feature that should be at the top of the list of things to look for in your next car. They reduce fatalities by 26 percent to 52 percent depending on the type of air bag and body style of the car, according to the Insurance Institute for Highway Safety.

Finding a car equipped with air bags that will protect all your passengers won’t be easy. While this technology has also been around since 1995, it’s only since the 2007 model year that more than 50 percent of vehicles have head-curtain and torso-type side air bags as standard equipment. While 77 percent of new cars, SUVs and pickups offer both types of air bags, the design and coverage varies widely between makes and models.

As a result, car shoppers need to do a bit of extra legwork to see if the car they are considering has side airbags that will protect all their passengers. Use the manufacturer’s website or the car’s brochure to find a picture of the air bags deployed to see what kind of coverage they provide.

For head-curtain air bags, check if they inflate to cover all seating rows and how far down the window they go. The larger the air bag, the more protection it will provide to shorter people such as children. For torso-type air bags, check if they provide protection for the driver, both front-seat occupants or all occupants, even in the rear seat. Research by the Insurance Institute for Highway Safety indicates that torso-type side air bags mounted in the rear can also provide some head protection to children.

If you are shopping for a new car, there are four other car safety features that hold promise that are on a small number of cars: adaptive headlights, which move to follow the road, and systems that warn the driver of a possible forward collision, if the car wanders out of its lane or of a possible blind-spot collision. Some can respond with braking or steering. While these car safety features may prove to be worth the extra expense, more research needs to be done before we’ll know if they are worth the money.

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If you have a car question, e-mail it to us at Driving for Dollars. Read more Driving for Dollars columns and Bankrate auto stories.

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