Crash safety ratings are based on sound scientific and statistical analysis of real-world crash data and have been proven to save lives.
The process is essentially this: the IIHS looks at the most common crash scenarios which involve fatalities. They replicate the the crashes in a lab to gather data on the forces exerted on occupants during the crash. Then a test scenario is formalized and future vehicles will be scored based on the forces exerted on occupants during the crash and whether such forces are survivable.
Auto manufactures are supplied information about the tests are are given an opportunity to design their vehicles to perform well in crash testing.
Note, that the IIHS is a independent scientific organization dedicated to reducing fatalities and injuries in motor vehicle accidents and is supported by car insurance companies. These companies wouldn't be funding the IIHS if it didn't have a measurable payoff (humans are expensive to fix).
I was unable to find a relationship between IIHS safety ratings and IIHS driver death rates for trucks and SUVs based on the most recent set of data released (though this was in 2014, so maybe they have improved their testing methodology since then). Interestingly, the only two vehicles to receive "TSP+" ratings in 2014 were actually among those that driver was most likely to die in - the GMC Terrain and the Chevy Equinox.
So far, the only variable that I've found that is predictive of driver mortality is curb weight, and the relationship is not linear. There is a mortality minimum between 4000 - 5000 lbs of curb weight.
Again, this is just for trucks and SUVs, and just those 37 models that offered both 2WD and 4WD versions. Maybe the ratings work better for sedans or for other types of vehicles.
The process is essentially this: the IIHS looks at the most common crash scenarios which involve fatalities. They replicate the the crashes in a lab to gather data on the forces exerted on occupants during the crash. Then a test scenario is formalized and future vehicles will be scored based on the forces exerted on occupants during the crash and whether such forces are survivable.
Auto manufactures are supplied information about the tests are are given an opportunity to design their vehicles to perform well in crash testing.
Note, that the IIHS is a independent scientific organization dedicated to reducing fatalities and injuries in motor vehicle accidents and is supported by car insurance companies. These companies wouldn't be funding the IIHS if it didn't have a measurable payoff (humans are expensive to fix).