The IIHS performs two frontal tests: the moderate overlap test (top left) and small overlap test (top right).
“The crash tests follow what we’re seeing in the real world,” Rader said. “Frontal impacts, for example, are the most common type of collision in fatal crashes.”
Both tests have adult-sized test dummies in the seats. In the moderate overlap frontal test the car travels at 40 MPH towards a barrier roughly two feet tall. Forty percent of the total width of the vehicle will strike the barrier on the driver side to simulate two cars hitting each other on their driver’s sides.
The small overlap test simulates the car hitting a utility pole, tree, or another vehicle with less contact than the previous test. The car travels at 40 MPH towards a barrier that’s about five feet tall, and the contact occurs at the corner of the car with about 25 percent of the total width hitting the barrier on the driver’s side. This test is a tough one for automakers to prepare for, as the occupants move in two directions: forward and toward the side of the vehicle.
Additionally, the impact at the corner of the car could cause the wheel or suspension to move towards the driver, potentially pushing into the cabin.
“We launched the small overlap front test in 2012 after research showed that about a quarter of the serious injuries and deaths that still occur in frontal crashes are in small overlap collisions,” Rader said.
Data is gathered from these two tests by using advanced crash test dummies that are outfitted with sensors. These sensors can detect the pressure and forces that would be experienced by a human passenger in order to determine what sort of injuries the crash could cause.
Additionally, the dummies are covered in colorful “grease-paint” that spreads to whatever it touches. This allows the crash-test engineers see where and what the dummy is making contact with during a crash. If all goes according to plan, the engineers would only see the paint on the airbags.
Finally, IIHS engineers examine how the vehicles cabin stays intact during a frontal crash. Assessment of the moderate overlap test includes nine areas where the cabin can deform and injure an occupant. The small overlap test looks at 16 areas.
All of these factors are combined to give a rating. According to a study conducted by the IIHS, the driver of a vehicle rated “Good” in the moderate overlap test is 46 percent less likely to die in a frontal crash compared with a driver of a vehicle with a “Poor” rating. Drivers in vehicles with “Acceptable” or “Marginal” ratings are 33 percent less likely to die than in a “Poor” vehicle.