There's been considerable debate between automakers, legislators and safety advocates over how roof strength correlates to deaths in rollover crashes. The majority of the focus has appropriately been heaped on SUVs, whose high center of gravity makes them more prone to rollovers, particularly when they leave the road.
The Insurance Institute for Highway Safety has just released a study that proves that more roof strength can reduce injuries by some 39 to 57 percent when compared to the weaker models it tested. The IIHS used the same roof strength test as the feds on a group of SUVs that currently meet the government's roof requirements. At the top of the heap was the 2000-2004 Nissan Xterra that was able to withstand almost 12,000 pounds of force, while the lowest ranked vehicle, the 1999-2004 Jeep Grand Cherokee, lost its head(room) after 6,500 pounds of force was applied to the roof.