What You Need To Know About IIHS Car Crash Tests

crash test IIHS

Photo source: http://www.thecarconnection.com/news/1093800_the-safest-cars-of-2014

IIHS tests assess 2 aspects: crash worthiness (how well a car secures its passengers in a crash) and crash mitigation and avoidance (technologies that avoid a crash or at least reduce the damages).

To figure out the crashworthiness of a vehicle, IIHS rates whether cars are good, acceptable, poor or marginal, based on its performance in 5 tests: small overlap front, moderate overlap front, roof strength, side, and head restraints.

In terms of crash mitigation and avoidance, IIHS gets to assign cars with available front crash prevention systems ratings (basic, advanced, superior), based on the kind of performance or system it exudes during the track tests.

About IIHS Car Crash Tests

Again, the IIHS examines the crashworthiness of a vehicle with the 5 tests mentioned (small overlap front, moderate overlap front, roof strength, side, & head restraints). For front car prevention rating, IIHS does assessments of the headlight systems & the child seat attachment hardware called LATCH. The descriptions here show how every test is done, and the results are translated to ratings.

A frontal crash is considered the most typical kind of crash which results in fatalities. Lots of movements have long been made for frontal security with the assistance of the NHTSA or National Highway Traffic Safety Administration which started in the 1970s. The crashworthiness assessments of IIHS started in 1995.

The institute does 2 types of frontal crash tests: the small overlap test and the moderate overlap test.

Moderate overlap frontal test

When the institute started its moderate overlap frontal exams, most of the vehicles were just rated marginal or poor. Now, lots of vehicles are already earning good ratings. The occupant compartments have been made way sturdier than before. They prevent crash and enable airbags and safety belts to work like magic.

During a moderate overlap frontal test, a car gets to travel 40mph to a barrier w/ a deformable face made from an aluminum honeycomb. This barrier face is more than 2ft. tall. A Hybrid III dummy which represents an average-sized man is placed in the driver’s seat. 40% of the whole car width hits the barrier on the side of the driver.

The tests’ forces are the same with the result of a frontal offset crash involving 2 cars with the exactly the same weight, both going just below 40mph.

Small overlap frontal test

In order to gain more enhancements in terms of frontal crash security, IIHS in 2012 headed a small overlap frontal crash test. This test was made to imitate what could happen if the car’s front corner gets to collide with another car or object such as a utility pole or a tree. The crash test could be a challenge for certain airbag and safety belt designs since the passengers or occupants may move both toward the car’s side and forward.

During a small overlap frontal test, a car could travel at 40mph to a 5 feet tall solid barrier. The Hybrid III dummy which represents an average-sized man is placed on the driver’s seat. 25% of the whole car width hits the barrier on the driver’s side.

Most of the modern cars comprise of safety cages that encapsulate the occupant’s compartment and is made to overcome head-on  collision and moderate overlap frontal crashes w/ minimal deformation. The major crush-zone structures are focused on the middle 50% of the front-end. If a car crash contains these structures and systems, the occupant compartment is secured from interference, and the safety belts and front airbags could effectively protect the occupants of the car.

A small overlap frontal crash mainly affects the outer edges of the car, which are not well-secured by the crush-zone structure. The crash forces readily into the suspension system, front wheel, and firewall. It’s common for the wheels to get forced rearward towards the footwall, furthering the interference in the occupant’s compartment and could lead to serious foot and leg injuries. To give an efficient security system in small overall crashes, the car’s safety cages have to resist the crash forces which are not tempered by the crush-zone structure. The front-end structure could also help.

Ratings criteria

Expert engineers have considered 3 main factors in determining how a car gets rated in the small overlap and modern overlap frontal tests in terms of injury measures, performance of the structure, & dummy movement.

Safety/ Structure cage: In order to measure a car’s structural performance, engineers gauge the extent of intrusion to the occupant’s compartment right after the crash. In a moderate overlap test, the measurement is taken at 9 locations around the driver sear. In the small overlap test 16 places on the driver’s side (interior or exterior) are gauged.

IIHS crash testPhoto source: http://money.cnn.com/video/pf/2014/01/22/iihs-small-car-crash-test.cnnmoney/

Understanding the ratings

So how do cars which earn good IIHS rating in the moderate overlap frontal test could perform in parallel to the real world crashes?

There’s an analysis from the 14-year  historical IIHS crash data which reveals that a driver of a car with good ratings in the moderate overlap test tends to have 46% chance of surviving in a frontal car as compared to a driver with a poorly rated vehicle. A driver of a car labeled marginal or acceptable is 33% less likely to face death in a frontal crash compared with one with poor ratings.

IIHS is just beginning to assess cars for security in case of a small overlap frontal crash. We do not have any comparable information on how cars will eventually fare. In retrospect, car manufacturers are swift in improving the security features of cars whenever the IIHS test program is modified. IIHS expects the same kind of response to the recent small overlap tests.

The test results of a frontal crash cannot be used to measure up car performance across different weight classes. That is basically because the applied kinetic energy in the small overlap and moderate overlap frontal tests will depend on the weight and speed of the vehicle under testing. Therefore, the crash becomes more critical for those cars with heavier weight.

With the equivalent frontal ratings, the one with more weight of the 2 cars usually offers better security in real world crashes. In the year 2009, IIHS has demonstrated this concept with their series of evaluation wherein small cars were purposely crashed to the larger ones, all of the those has a good frontal rating in the moderate overlap tests.

For you to keep updated about the ratings, access the test verification information from IIHS.

So how does the IHHS’ frontal crash test different from the
NHTSA’s New Car Assessment Program frontal test?

With regard to the NCAP or New Car Assessment Program (NCAP), occupants get crashed at 35 mph to a solid barrier with the whole vehicle’s width.

IIHS is running offset frontal tests rather than a series of full-width frontal test. In cases of crashes, only one side of the car’s front end and not the whole width gets to hit the barrier. Thus, there’s a higher chance that a small section of the structure has to control the crash energy and interference to the occupant compartment.

An offset test is way more demanding than a full-width test. While a full-width test is more demanding of the airbags and safety belts. In a full-width test, there’s less crushing of the car structure, so decelerations to manage are also greater. Generally, the tests offer a complete package of the frontal crashworthiness.

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