The National Highway Traffic Safety Administration has unveiled a free online service for drivers to find out if their vehicles have been recalled but not repaired.

The service started Wednesday on its website.

Drivers can key in their vehicle identification number to get the results. The number can be found on the dashboard near the windshield or on the driver's door post.

Also beginning Wednesday, automakers must keep recall data on their own websites, and update it at least once per week. 

The safety agency's site will show data if there's an open recall, or it will tell drivers there are none. The agency also says used-car buyers can check for unrepaired vehicles before they make a purchase.