NEW YORK (CNN/Money) - Electronic stability sensors seem to be effective in reducing rollovers and single-vehicle crashes, especially in SUVs, safety regulators said Thursday.

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A preliminary study by the National Highway Traffic Safety Administration (NHTSA) found that the sensor systems reduced single-vehicle crashes by 35 percent compared to the same models sold in prior years without the technology. The agency said 7.4 percent of passenger vehicles had some sort of electronic stability control system installed last year.

The electronic sensors detect when a vehicle is about to go out of control or roll over. Computers then automatically adjust engine power and apply braking to specific wheels to keep the vehicle under control. This can happen without the driver even being aware that a potentially dangerous situation ever existed.

For the small sample of SUVs in the study, single-vehicle crashes were reduced by 67 percent. The technology was also associated with a 30 percent reduction in fatal single-vehicle wrecks for passenger cars. Fatal single-vehicle crashes were reduced by 60 percent in SUVs equipped with the sensors.

The preliminary NHTSA study gauged the effectiveness of the sensor systems by looking at statistics for fatal and nonfatal crashes in five states from 1997 to 2003. The study examined crash statistics only for models equipped with the electronic stability control system (ESC) as standard equipment.

The SUV models in the study included Mercedes-Benz M-class vehicles, the Toyota 4Runner and Land Cruiser and Lexus RX300 and LX470.

The agency emphasized that the results are preliminary and studies involving larger numbers of vehicles could instill more confidence in the effectiveness of the ESC.