Over in the US, while the government has stalled on introducing tougher roof-strength standards for passenger cars, the Insurance Institute for Highway Safety (IIHS) has gone out and tested 12 small SUVs for roof strength, indicative of roll-over protection.

While Federal standards require a car to be able to support 1.5 times the vehicle’s own weight on its roof, the IIHS system will only award a ‘good’ rating to a vehicle capable of supporting four times its own weight. 

An ‘acceptable’ rating is applied to cars which can hold 3.25 times their weight and a ‘marginal’ rating given for cars which can hold 2.5 times their own weight. The strength-to-weight ratio of 2.5 is also the same figure being proposed as the new Federal standard. Currently anything that tests below 2.5 is rated as ‘poor’ by the IIHS.

Out of the field of twelve small SUVs, only four returned a ‘good’ result. The Volkswagen Tiguan topped the field followed by the Subaru Forester, Honda Element and Jeep Patriot. In the ‘acceptable’ range were the Nissan Rogue (Dualis), Toyota RAV4, Chevrolet Equinox and Mitsubishi Outlander.

At the bottom end of the field, the Honda CRV and Ford Escape received a ‘marginal’ rating and the Kia Sportage was the only car tested with a strength to weight ratio below 2.5, earning it a ‘poor’ rating.

The IIHS conducts its roof-strength test by pushing a metal plate at constant speed against one side of a vehicles roof. To earn a good score, a vehicle must withstand four times its own weight before the roof has sustained five inches (12.7 cm) of crush.

The Institute also conducts a Top Safety Pick award which will now require a ‘good’ rating for roof crush strength to qualify.

For 2010 the Institute expects less cars will be eligible for the award, with the field of eight small SUV Top Picks narrowed down to just three contenders this year, the Tiguan, Element and Forester.