Washington ? General Motors Corp. on Wednesday unveiled a new OnStar vehicle communications service that will determine within seconds of a crash how serious the impact was and automatically call for help.

Crash sensors in the front and rear bumpers and just behind the driver’s door can tell where the vehicle was hit and the speed and force of impact.

Beginning in some vehicles next year, the information will be sent to an OnStar operator through a handsfree cellular phone connection. The operator can talk to the crash victims in the vehicle and conference in 911 dispatchers with all the information they need to send emergency responders.

OnStar is the country’s most popular in-vehicle communications system, with more than 2 million subscribers.

The system already alerts an OnStar operator when an air bag deploys, but the improvements will notify operators about accidents that did not trigger an air bag deployment and send more information about the crash.