Federal Motor Vehicle Safety Standard (FMVSS) No. 216, Roof Crush Resistance, establishes a minimum requirement for roof strength to "reduce deaths and injuries due to the crushing of the roof into the occupant compartment in rollover crashes." In this test, a rigid plate is pushed into one side of the roof at a constant speed. The roof must be strong enough to prevent the plate from moving 5 inches when pushed at a force equal to 1½ times the weight of the vehicle. The test went into effect in 1973 and remained essentially unchanged until an updated rule was announced in 2009.
The new rule requires that a roof withstand an applied force equal to 3 times the vehicle's weight while maintaining sufficient headroom for an average size adult male. While both sides of a vehicle's roof were required to meet the former standard, only one side was tested on any given vehicle. The new rule requires a second test of the same vehicle's roof on the opposite side. The new standard is being phased in beginning with 2013 model vehicles, and by the 2017 model year, 100 percent of each manufacturer's fleet must comply.
The updated FMVSS 216 regulates the roof strength of many SUVs and pickup trucks by extending coverage to vehicles with gross weight ratings (GVWRs) up to 10,000 pounds. (GVWR is the weight of the vehicle plus the maximum load of passengers and cargo specified by the manufacturer.) In the past, the standard applied only to vehicles with GVWRs up to 6,000 pounds, which meant about 44 percent of the SUV and pickup fleets were exempt.
While the updated roof strength regulation applies to these vehicles, they aren't subject to the same force requirements. Instead of a force equal to 3 times the vehicle's weight, vehicles with GVWRs over 6,000 pounds are subject to a force equal to 1½ times their weight.
A second federal standard for rollover crashworthiness went into effect beginning with 2014 models. FMVSS No. 226, Ejection Mitigation, applies to side curtain airbags. The intent of the standard is to ensure that, when deployed, such systems are sufficiently large and strong enough to prevent ejection through the side windows. While this could be a positive step for further reducing rollover injuries, the standard will not test whether the restraint systems actually deploy properly in rollover crash conditions.