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Understanding Crash Test Ratings

When shopping for a new vehicle, consumers undoubtedly do some checking up on its safety features and crash test ratings.  Entities like insurance companies and car manufacturers conduct independent studies regarding vehicle safety and publish them in order to assist consumers in making safe, educated decisions.  Often times these ratings can be confusing, consisting of numbers and statistics accompanied by designations like “Top Safety Pick”, the criteria of which the average American may be unfamiliar.  A breakdown of the Insurance Institute for Highway Safety’s (IIHS) rating criteria is essential for understanding how vehicles are evaluated for safety.

The IIHS focuses on two facets of safety when conducting their analysis—crashworthiness and crash avoidance and mitigation.  Crashworthiness, or a vehicle’s ability to protect its occupants in an accident, is based on how the vehicle performs in five tests:

  • moderate overlap frontal test,
  • small overlap frontal test,
  • side crash test,
  • roof strength and
  • head restraint evaluation.

A vehicle gets its crash avoidance and mitigation rating based on what technology it is equipped with that can prevent a crash or lessen its severity.  Only vehicles with front crash prevention systems are rated for crash avoidance and mitigation.  The results are then translated into overall ratings of good, acceptable, marginal, or poor for each category.

Why Do Crash Test Warnings Matter to Me?

On a busy Monday morning in the Chicagoland area a commuting driver may face many hazards.  Speeding vehicles, large trucks, and low visibility turns are just a few commonly found hazards throughout the area.  Recently, the driver of a dark blue BMW X1 became the victim of these hazards when her vehicle was struck by a dump truck on northbound Route 41, south of 137 in North Chicago just before 1 p.m.  It took collaboration by the North Chicago, Libertyville, Knollwood, and Great Lakes Fire Departments to stabilize the vehicle and extricate the driver, who was pinned inside.  She was airlifted to the hospital but is expected to survive perhaps, in part, due to the safety features of her vehicle.  The BMW X1 was given the highest safety rating of ‘good’ in 4 out of 5 of the categories tested by the IIHS.  The only category in which the SUV received a score of ‘marginal’ was in the small overlap frontal test.  The BMW X1 does not feature a front crash prevention system and is therefore not rated for its crash avoidance and mitigation rating.

Moderate Overlap Frontal Crash Test

Applied in real life, a moderate overlap frontal test most closely replicates an offset, head on collision between two vehicles of similar weight both travelling at about 40 mph A frontal crash is the most common type of fatal car accident.  The moderate overlap frontal test exposes 40% of the front of the vehicle to a barrier made of aluminum honeycomb at a speed of 40 mph.  A crash test dummy the size of an average man with sensors in its head, neck, chest, legs and feet is situated in the driver’s seat to measure the potential for injury when the vehicle hits the barrier on the driver side.  This results in the occupant compartment going through greater deceleration making this test more appropriate for evaluating restraint systems such as airbags and seat belts.  .

Small Overlap Frontal Crash Test

A small overlap frontal test simulates a crash where the front corner of the vehicle hits a stationary object such as a pole or tree.  Small overlap frontal crashes primarily affect a vehicle’s outer edges, which aren’t well protected by the crush-zone structures.  Because 25% of frontal crash deaths are caused by car accidents in which the outer front wheel is the first point of impact, the IIHS recently implemented the small overlap frontal test.  Seriously injuries resulting from these types of accidents typically include trauma or entrapment to the leg or foot.

Side Crash Test

A side crash test simulates an SUV t-boning the driver’s side of a vehicle at 31 mph.  It is actually a very extreme simulation which, in real life, would be unlikely to produce an uninjured passenger.  The goal however, is that conducting a side crash test will provide direction to car manufacturers regarding the best way to design cars that will decrease the severity of any injuries.  Because women are more likely to suffer from a head injury following a left-side impact the IIHS positions crash test dummies in both the driver seat and the seat behind which are equivalent to a petite woman or 12 year-old child.

Roof Strength

Rollover crashes carry the highest risk of fatality when compared to any other type of accident.  In instances when a rollover does result in a fatality, more often than not the victim was not wearing a seatbelt.  The roof strength test consists of a metal plate being pushed against one side of the roof at a slow, constant pace.  The peak strength-to-weight ratio of the roof is recorded at any time before the roof is crushed by 5 inches.  A good roof strength rating requires that a roof can withstand a force of at least 4 times the vehicle’s weight. Stronger roofs and side curtain airbags can help protect occupants during a rollover accident but the best way to avoid injury and ejection is for each passenger to wear their seat belt correctly at all times.

Head Restraint Evaluation

The  head restraint evaluation is conducted by simulating a rear-end crash equivalent to if a stationary vehicle were struck by a vehicle of similar weight at 20 mph.  According to the IIHS, neck sprains and strains are the most frequently reported injuries in U.S. auto insurance claims.  Although whiplash-type injuries can result from any number of automobile accidents, rear-end accidents are the most common culprit.  The head restraint evaluation tests the effectiveness of head restraints in preventing head, neck, and spinal injury.  In this crash test, a dummy about the size of an average man with a spine designed to mimic a humans 24 vertebra is placed in the driver seat to measure the impact the accident would likely have on a real driver.

R.F. Wittmeyer

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