Mustang first ragtop to ace NHTSA crash tests

The 2008 Ford Mustang is the first convertible to ever earn five-star ratings in all crash tests performed by the federal government's National Highway Traffic Safety Administration, Ford announced Thursday.

Five stars is the highest possible rating in those tests. The Mustang earned five stars for front crash safety for both the driver and passenger as well as five stars for side impact for both front and back passengers. The Mustang convertible also earned five stars for rollover resistance, a measure of how likely a vehicle is to roll over during an abrupt maneuver.

2008 Ford Mustang convertible

All five categories have existed since 2001 when NHTSA added a rollover rating based on laboratory tests.

The results apply to 2008 model year Ford (Charts, Fortune 500) Mustangs. Side airbags are standard equipment on 2008 Mustangs but were optional in previous model years.

The hardtop version of the 2008 Mustang also earned five stars in all but one of NHTSA's crash tests. The hardtop Mustang earned four stars for rear passenger protection in side impacts.

The Mustang convertible may have earned a higher score for rear passenger protection because of additional metal structure added to the convertible's body to help resist flexing.

Without a roof, convertible cars' bodies are more prone to twisting during driving which can adversely affect handling. Most convertibles have additional support added to the body to prevent twisting and in this case, Ford spokesman Dan Jarvis theorized, that added structure may also have improved the convertible's performance in the side crash test.

In NHTSA's front impact test, vehicles are crashed into wall at 35 miles per hour. The test is designed to mimic a head-on crash between two similar-sized vehicles at that speed. In NHTSA's side impact test, the vehicle is struck from the side by a 3,015 pound barrier moving at 38.5 miles per hour.

To rate rollover resistance, NHTSA determines a vehicle's center of gravity, a measure of how top-heavy it is, using laboratory tests. A driving test, added in 2004, is also conducted if laboratory tests indicate a vehicle might tip during a sudden maneuver.

The Mustang convertible didn't do quite as well in crash tests conducted by the privately funded Insurance Institute for Highway Safety. In IIHS tests, the Mustang convertible earned the top score for side impact protection, but rated only Acceptable, the second-best score, for front impact protection. The Insurance Institute gave the Mustang a Poor rating for whiplash protection from rear impacts. NHTSA does not rate vehicles for whiplash protection.