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What Are IIHS Safety Ratings and Where Do They Come From?

Photo by Simon Yeo / Flickr / CC BY 2.0

Have you ever wondered how car safety ratings happen? We see them all the time in consumer reports, but what do they actually mean?

If you’ve ever researched a vehicle’s overall safety, you’ve doubtlessly encountered safety ratings by the Insurance Institute for Highway Safety, or IIHS. Like many people, though, you’ve probably taken those ratings for granted and have little idea about how they are calculated.

By learning the basics of how the IIHS tests car safety, you can gain a better understanding of vehicle safety and how far it has come.

What is the IIHS?

The Insurance Institute for Highway Safety, or IIHS, was founded by three major insurance associations in 1959 with the initial goal of supporting highway safety efforts. Today, the IIHS is a non-profit, independent, scientific/educational organization that strives to reduce injuries, deaths and property damage caused by crashes. While crash prevention was once the organization’s primary goal, the focus has now shifted to investigating the factors that cause crashes using a modern, scientific approach.

Crash Factors

Modern vehicle accidents are typically caused by one of the following three factors:

  • Physical Environment – The IIHS assesses the designs of modern roadways and works to eliminate roadside hazards and to reduce accidents caused by vehicles running off the road.
  • Human Factors – Such factors include driver fatigue, teenage drivers and drunk drivers, but the use of safety restraints and other preventive measures are considered as well.
  • Vehicle Research – This is where IIHS vehicle safety ratings originate. The focus here is on crashworthiness and crash avoidance.

Vehicle Research Center

In 1992, the IIHS founded the Vehicle Research Center in Virginia. This is where car safety tests are conducted. The primary objective of the VRC is to encourage car manufacturers to produce safer cars. This is largely accomplished by publishing car safety ratings, which have a major impact on consumers’ buying habits.

Safety Tests Overview

At the Vehicle Research Center, the IIHS conducts vehicle safety tests that fall into two broad categories:

  • Crashworthiness Tests – These tests are concerned with how well a vehicle protects the occupants of a vehicle during a crash.
  • Front Crash Prevention Tests – These tests evaluate systems that are designed to warn drivers and/or make the car brake automatically in order to mitigate or avoid frontal collisions.

IIHS Vehicle Safety Tests

When you peruse a site like Edmunds.com to conduct research about a vehicle, you’ll notice that safety ratings are almost exclusively provided by the IIHS. Those ratings are the result of crashworthiness tests that are conducted by the IIHS at its VRC in Virginia. The tests conducted by the IIHS assess three factors: Structural Performance, Injury Measures, and Dummy Movement.

Structural Performance: This factor concerns how much an object, such as an oncoming vehicle or roadside hazard, intrudes into the passenger compartment of a vehicle. The less it intrudes, the more positive this factor is deemed to be.

Injury Measures: Passengers aren’t immobile, of course, so structural performance is just one part of the puzzle. To take into account how people move during a collision, dummies are fitted with special sensors. Following a test, the sensors are assessed to determine the likelihood of various injuries.

Dummy Movement: Greasepaint is placed on dummies’ knees, lower legs and heads to determine where various body parts come into contact with vehicle components during collisions.

The IIHS awards one of four ratings – good, acceptable, marginal and poor – for each of the following five tests:

  • Moderate Overlap Frontal Test – In this test, which was previously known as the frontal offset test, the car is driven at 40 miles per hour toward a two-foot-tall barrier with a deformable face. About 40 percent of the width of the vehicle strikes the barrier on the driver’s side.
  • Small Overlap Frontal Test – Introduced in 2012, this test assesses the effectiveness of seatbelts and airbags during collisions between the corners of vehicles and other cars and/or objects. A car is driven at 40 mph into a rigid, five-foot-tall barrier, and 25 percent of the width of the vehicle makes contact.
  • Side Crash Test – In this test, which was introduced in 2003, an SUV-like barrier weighing 3,300 pounds is rammed into the driver’s side of a vehicle at 31 mph. Two smaller dummies are in the vehicle to assess injury measures, head protection and structural performance.
  • Roof Strength Test – To test the performance of a vehicle during a rollover accident, the IIHS conducts this test. A metal plate is pushed against one side of a car to test the strength of its roof. The resulting strength-to-weight ratio reflects its overall strength. To earn a rating of good, a car must receive a strength-to-weight ratio of at least four, which means its roof is capable of withstanding a force that’s at least four times its total weight.
  • Head Restraint Test – Neck sprains, or whiplash, are the most frequently reported injuries caused by vehicle accidents. This test assesses the quality and effectiveness of restraints that are designed to reduce the risk of such injuries. A geometric rating and dynamic rating are combined to arrive at an overall rating.

Top Safety Picks

Since 2006, the IIHS has awarded Top Safety Pick ratings to vehicles that earn good ratings in moderate overlap, side crash, roof strength and head restraint tests, as well as a good or acceptable rating in the small overlap test. More recently, the IIHS started awarding Top Safety Pick Plus, or TSP+, ratings to vehicles that not only meet all TSP criteria but that also achieve basic, advanced or superior ratings for front crash prevention.

In 2014, three Subaru vehicles were awarded the TSP rating: the 2014 Subaru Impreza, the 2015 Subaru WRX and the 2014 Subaru XV Crosstrek. Three others – the 2014 Subaru Legacy, the 2014 Subaru Outback and the 2014 Subaru Forester – received TSP+ ratings.

Since its founding, the IIHS has played a pivotal role in reducing the number of car accident fatalities. The organization continually sets up new safety guidelines and adds new tests as technologies evolve and improve. As such, the ratings it provides are very useful to anyone who is researching a new car.

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