The U.S. Department of Transportation mandates that all new vehicles pass Federal Motor Vehicle Safety Standard (FMVSS) performance tests. These tests ensure vehicles maintain a minimum safety standard. Standards concerning windshields are:
FMVSS 212 measures windshield retention in a barrier crash. Every make and model vehicle is accelerated to 30 mph and crashed head-on into a concrete barrier. The automobile must retain 75 percent of the windshield along the pinchweld perimeter. Some vehicle manufacturers require 100% retention in this severe crash test.
FMVSS 216 is the roof crush performance test. It measures the structural strength required to protect occupants in the event the vehicle rolls over. One and one-half times the unloaded vehicle weight or 6,000 lbs. (whichever is less) of force is applied at an angle to the roof. The roof structure can depress no more than five inches to pass. Note: the windshield provides 30-70% of the roof strength.
FMVSS 208 occupant crash protection specifies equipment requirements for active and passive restraints, including air bags. There can be no separation of load-bearing safety assemblies in a 30 mph barrier crash. This pertains to the windshield because the passenger side air bag deploys off the windshield in order to perform its safety function.