NHTSA and IIHS Overview
Two groups test passenger safety in cars. The first one is the National Highway Transportation Safety Association (NHTSA). The other group is the Insurance Institute for Highway Safety (IIHS).
Curious about your car? Visit NHTSA's Safer Car site and IIHS's vehicle ratings.
The NHTSA is a government agency. It regulates safety for vehicles. Their goal is to improve protection for women and children in crashes. They are instrumental in upgrading the safety requirements for cars sold in the U.S.
A group of motor vehicle insurers funds the IIHS. Their goal is to improve occupant protection in cars in order to minimize loss claims. While it may seem like the IIHS might be focused more on dollars than lives, their efforts have made major contributions to improving the overall safety of vehicles.
The following describes tests that the NHTSA and IIHS perform.
NHTSA Frontal Impact Test
The NHTSA frontal impact test assesses seat belts and air bags. The risk of serious injury is assessed using head and chest injury risk. Injuries to these body regions carry the greatest chance of causing a fatality.
Here’s how it works. A test vehicle crashes into a barrier at 35 mph. This simulates an impact with an identical vehicle. This type of crash typically causes serious injury.
A test dummy in the test car represents an average sized male. A "5-star" rating means there is a 10% or less risk of serious injury to the head and/or chest. This test simulates a vehicle crashing an identical car. Therefore, it would not necessarily represent all crashes. For example, test results may not reflect a situation such as an impact between a compact car and a large truck. In those kinds of crashes, the occupants of the smaller car are more at risk.
More frontal impact test information is on this NHTSA page.
IIHS Offset Frontal Test
The IIHS offset frontal test is the test most people might recall seeing on the T.V. show Dateline. It represents a more severe crash than the NHTSA test, and is performed at a speed of 40mph.
This test presents a challenge to the vehicle structure as well as the belts and bags, as the impact is borne by 1/2 of the vehicle's front end rather than the full frontal impact seen in the NHTSA test. It simulates a vehicle impacting with an identical vehicle, as does the NHTSA frontal test.
Performance is assessed using head, neck, chest and leg injury risk. The test measures the vehicle crush and the survival space around the occupant. Learn more about the IIHS offset frontal test here.
NHTSA Side Impact Test
The NHTSA side impact test represents a 90-degree (T-Bone) intersection impact. A 3,015lb "striking car" crashes into a stationary "struck vehicle" at a speed of 38.5 mph.
The wheels of the striking car are at an angle. This gives the impact force a direction that reflects the relative motion of the two cars. The impact targets both driver and rear seat occupant positions.
The struck vehicle represents an average car weight and geometry of cars found on the road in 1990. The test dummy represents an average adult male in both driver and rear passenger positions.
The side impact test evaluates injury risk in terms of chest and pelvis injury. Many life-threatening injuries in side impact crashes occur in these regions.
Currently the NHTSA is working on a more stringent side impact test. The new test takes into account head injury risk. Also, a new pole impact test will simulate side impacts into utility poles.
IIHS Side Impact Test
The IIHS side impact test looks at an SUV or Pick-Up impacting the test vehicle. Crash statistics show there is a higher risk of fatality to an occupant when these types of cars strike them. The simulated "striking vehicle" is higher off the ground, taller, and slightly heavier (3,300 lb) than the one used in the NHTSA side impact test.
The "striking vehicle" hits at 90 degrees to the stationary "struck car" at 31 mph. This differs from the NHTSA test in which the striking car's wheels are not turned.
The injury risk is assessed using a dummy representing a small female in the driver and rear passenger position. This size dummy also represents an average 12 year old. It differs from the dummy used in the NHTSA side impact test. The IIHS dummy represents occupants with the highest risk of serious injury from side impact crashes.
NHTSA Rollover Test
The NHTSA rollover rating measures the risk of rollover, not a risk on occupant injury in rollover. The test evaluates two factors. One is the static stability factor. The other one is performance in a dynamic maneuvering test that causes a rollover.
The vehicle's geometry determines the static stability factor. The geometry is the height of the car's center of gravity and the distance between the wheels. NHTSA work indicates that this number is a fair measure of the risk of rollover for a tripped car. Examples of tripped rollovers include when a car leaves the road and gets into loose gravel, or when it hits a curb. These types of rollovers account for the vast majority of rollovers.
The dynamic maneuver test measures whether or not the wheels leave the ground when the car drives through a quick, tight turn. Rollovers induced by these types of driving motions are rarer.