Millions of Americans have had their cars stolen or hijacked, according to the Automobile Club of America.

More than 20 percent of the victims left the keys in the ignition and more than 80 percent left the doors unlocked. Motorists should always take the keys and lock the doors, according to AAA.Car jackers approach the vehicle - usually with a gun or knife - while the owner is inside it. The assailant orders the driver out - or in extreme cases, shoots or kidnaps the victim.

The organization offers additional tips to avoid becoming a victim:

- Before getting in the car, check for flat tires, objects blocking the tires or people hiding underneath.

- Check the back seat before getting in to make sure nobody is inside. At night, carry a light to check the vehicle.

- Park under bright lamps, preferably around a lot of people.

- Try approaching the car on the driver's side. This will prevent surprise if an assailant is hiding near the door.

- Survey the vehicle from a distance before approaching.

- Have your keys ready to go before you reach the vehicle. Don't search your pockets for them when you get to the car.

- If you see a suspicious person around a car, walk to a public place and seek help.