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Safety According to the IIHS

Safety According to the IIHS

By Jeff Youngs, February 24, 2012
Each year, more than 30,000 passenger-vehicle occupants die in crashes on U.S. roads. Given the risks, safety should factor into your purchase decision just as much as or more than any other feature, especially if you're buying a family car. Today's cars are all far safer than those of the past, but some are still considerably safer than others.

Finding Safety Data
The main two organizations that perform automotive safety testing are the National Highway Traffic Safety Administration (NHTSA) and the Insurance Institute for Highway Safety (IIHS). Both have easy-to-use Web sites ( and that provide vehicle ratings, along with safety tips and many other features. For purposes of this article, we'll focus on the IIHS, its mission, how it tests vehicles, and the results of the latest testing.

History of the IIHS
While the NHTSA is a government agency, the IIHS is a nonprofit organization supported by insurance companies. According to its Web site, the IIHS is "uniquely positioned to influence highway safety issues because the interest of insurers in reducing highway losses coincides with the public interest." The IIHS is also affiliated with the Highway Loss Data Institute (, which publishes data on insurance loss variances among different kinds of vehicles.

The IIHS was founded in 1959 to act as "a conduit for insurers to support academic and other organizations working in the field of highway safety." In 1968, the Institute became a research organization. Today it is a scientific research and communication group that conducts "science-based research to reduce deaths, injuries, and property damage on the nation's highways."

The Institute opened its Vehicle Research Center (VRC) in 1992. The Center's research falls into three categories: human factors, such as drunk driving and teenage drivers; vehicle factors, including crash avoidance and crashworthiness; and the physical environment, which involves assessing roadway designs. The IIHS began publishing frontal crash test information for consumers in 1995. Side tests were added in 2003 and rear tests in 2004.

Crash Testing Creates Safer Vehicles
Largely due to the efforts of the IIHS and NHTSA, today's vehicles are safer than those of the past, especially in frontal crashes. Air bags, improved structural designs, and higher seat belt-use rates have all made a big difference. According to the IIHS, from the early 1980s until 2000, driver death rates per million cars registered decreased 47 percent. That included a 52-percent decrease for frontal crashes and a 24-percent decrease for side-impact crashes.

Side-Impact Death Rates Have Risen
As front-impact protection has improved and consumers have shifted toward heavier, higher-riding trucks and SUVs, the percentage of deaths due to side impacts has risen. In the 20 years from 1981 to 2001, deaths in frontal impacts declined from 61 percent to 43 percent of the total. During the same time, driver deaths caused by side impacts with another passenger vehicle rose from 31 percent to 51 percent of the total. In 2000-01, almost 60 percent of the vehicles struck on the driver's side, in which the driver was killed, were hit by SUVs or pickups-up from about 30 percent in 1980-1981.Given these numbers, it is more important than ever to choose a vehicle with side and curtain air bags.

The IIHS makes the results of its testing available on its Web site. If you're interested in buying a car, it's a good idea to look up the test results for the models you're considering. But what do those results mean? Let's take a look at the IIHS's testing procedures to get a better understanding of how a highly rated vehicle makes you safer.

Testing Procedures
The IIHS conducts crash tests to evaluate front, side and rear crashworthiness. A vehicle can earn one of four possible ratings in each test: Good, Acceptable, Marginal or Poor.

Frontal Offset Test: The frontal test is a 40-mph offset crash with a dummy representing an average-size male placed in the driver's seat. In the test, 40 percent of the front vehicle width strikes a barrier on the driver's side. The barrier is made of aluminum honeycomb, which the IIHS says makes the forces in the test similar to those involved in a frontal offset crash between two vehicles of the same weight, each going just less than 40 mph.

This test is especially important because about half of the fatalities each year occur in frontal crashes. In IIHS testing, the vehicle is evaluated based on measurements of intrusion into the occupant compartment, injury measures recorded on the dummy, and analysis of slow-motion film to assess how well the restraint system controlled dummy movement during the test.

The dummy's head, neck, chest, legs and feet are assessed for injury. The slow-motion film shows how well the seat belts, air bags, steering column, head restraints and other restraint features control dummy movement. It is important that the vehicle's restraints keep the dummy from moving around too much and resulting in bodily impact with interior parts or a partial or complete ejection from the occupant compartment.

Intrusion on the vehicle's safety cage is measured in 10 places in the driver's seating area, including two steering wheel measurements, and the front crush zone is evaluated for how well it managed the crash energy.

The IIHS's frontal test differs from the NHTSA's New Car Assessment Program (NCAP) test. The NCAP test is performed at 35 mph with a full-width rigid barrier that is hit head-on, impacting the entire front of the vehicle. The IIHS says its test complements the NCAP test. According to the IIHS, the NCAP test maximizes energy absorption so that the integrity of the occupant compartment, or safety cage, can be maintained well in all but very high-speed crashes. The full-width test is also very demanding of restraint systems. The IIHS's offset test, on the other hand, requires a smaller area of the structure to manage crash energy. This increases intrusion into the occupant compartment on the driver's side.

The IIHS has seen considerable improvement in frontal offset crash-test results since it started doing the test in 1995. When the Institute started its testing, about half of the vehicles earned "Marginal" or "Poor" ratings and more rated "Poor" than "Good." Today, almost every passenger vehicle earns a "Good" rating. However, the results should not be used to compare vehicles of different weight classes. Given equivalent ratings, simple physics dictate that a heavier vehicle will usually be safer in a crash.

Side-impact Test: The IIHS's side-impact crash test involves a vehicle with dummies in the driver's seat and the rear seat behind the driver. The dummies are small, representing small adult females or 12-year-old children. The IIHS says it uses dummies of this size for two reasons. First, women have been shown to be more likely to suffer serious head injuries in real-world crashes. Second, the heads of dummies of this size are more likely to sit lower and be subjected to possible impact by the oncoming vehicle.

The vehicle undergoing the test is struck perpendicularly in the side by a barrier that weighs 3300 pounds moving at a speed of 31 mph. The barrier represents the front end of a pickup or SUV. The Institute's ratings are based on injury measures recorded on the dummies, assessment of head protection countermeasures, and the vehicle's structural performance during the impact. The injury measures determine the likelihood that the driver and/or passenger would sustain serious injury to the head, neck, chest, abdomen, pelvis and femur. How the dummies heads move, and whether they contact any surfaces, are also evaluated. Structural performance is determined by how far the B-pillar (the side pillar behind the driver's door) intrudes into the occupant compartment.

The government's NCAP program performs a similar side-impact crash test. The difference is in the height of the moving barrier. The NCAP test's barrier is lower, representing a car. The IIHS says its test is more demanding because there is a greater risk of head injury due to the higher impact point. The IIHS notes that vehicles that earn a "Good" rating have side air bags, which have been shown in studies to substantially reduce the risk of fatality in side impacts.

When buying a car with side air bags, it's best to check all the option boxes. Seat-mounted front side air bags protect the torso. Curtain side air bags generally protect the head. And some curtain side air bags come with rollover deployment which allows them to remain inflated for an extended period of time for greater protection.

Rear-impact Test: The IIHS's rear-impact test is really a measurement of the effectiveness of a vehicle's driver's seat. Many vehicles are offered with multiple seating packages, so you should keep that in mind and look up the proper seating package on the IIHS Web site when making a purchase decision.

Rear crashes aren't as likely to cause life-threatening injuries as front and side impacts. The main injury in rear crashes is whiplash, which occurs when a rear impact causes the driver and seat to lurch forward. If the driver's head isn't properly supported, it will lag behind the body, which bends the neck and stretches it backward. A head restraint that stays close to the head can help prevent whiplash.

Whiplash injuries are expensive for insurance companies. According to the IIHS, two million neck injury claims are filed each year totaling $8.5 billion, or 25 percent of all injury claim dollars insurers pay out each year.

The IIHS gives out three rear crash protection ratings: a Seat/head restraint geometry rating, a Dynamic rating, and an Overall rating. The Institute first rates the seat/head restraint geometry. If it rates "Good" or "Acceptable," it is subjected to a dynamic test. Seat/head restraints with "Marginal" or "Poor" geometry aren't tested dynamically because they don't protect taller people in rear-end crashes. These seats are given a "Poor" overall rating.

For a seat/head restraint to receive a "Good" or "Acceptable" geometric rating, the headrest needs to be high and close to the back of the head. The IIHS says a head restraint should be no more than 9 centimeters (3.5 inches) below an average-size male's head and sit back no more than 10 centimeters (4 inches).

For the dynamic test, a dummy with a realistic spine and neck is placed in the seat. All restraints are used and the seat/head restraint is bolted to a sled. The sled is shot forward, mimicking a stationary vehicle being struck from behind by a vehicle of the same weight doing about 20 mph. This test assesses how well the seats support the torso, head and neck by measuring the time for the head to contact the restraint, torso acceleration, and forces on the neck. Better seats allow the head to contact the restraint quicker and exhibit slower torso acceleration. Neck forces are classified as low, moderate and high. A seat must have low neck forces and either low torso acceleration or quick time to head restraint contact to earn a "Good" rating.

Finally, the geometric and dynamic ratings are combined to determine an overall rating. It usually matches the dynamic rating.

Top Safety Picks
Each year, the IIHS releases its list of Top Safety Picks. According to the Institute, the automobiles named to this list offer "superior overall crash protection among the vehicles in their class." To qualify for the award, a vehicle must be equipped with electronic stability control (ESC) and earn the Institute's highest rating ("Good") in all three crash tests: front, side and rear. Vehicles such as the Ford Taurus, which offer electronic stability control as an option, only qualify as Top Safety Picks if they are equipped with ESC.

The Importance of Stability Control
The IIHS added the ESC requirement in 2007, based on research that showed the technology significantly reduces the risk of driver causation in a crash. According to the IIHS, ESC lowers the risk of a fatal single-vehicle crash by about half and lowers the risk of a fatal rollover crash by as much as 80 percent.

Electronic stability control, also called anti-skid control, is known by many names. General Motors calls its system StabiliTrak, Ford's is known as AdvanceTrac, and Chrysler dubs it Electronic Stability Program (ESP). Other proprietary names for this technology include Vehicle Dynamics Control (Subaru), Dynamic Stability Control (Volvo), Vehicle Stability Assist (Honda), and Vehicle Stability Control (Toyota).

No matter the name, ESC uses sensors to detect a loss of grip or vehicle instability, then works automatically with the anti-lock braking system to apply individual brakes to help keep the vehicle on its intended path. In some cases, ESC also reduces engine power.

With luck, you'll use ESC rarely, if ever. However, if you approach a corner too fast and your vehicle begins to plow straight ahead, ESC detects that the vehicle is not on its intended path and tries to correct the situation by applying the inside brakes. This will rotate the vehicle through the turn and probably save you from going off the road. Be aware that ESC can't defy the laws of physics, so it won't allow you to make a 90-degree left hander at 90 mph and it won't help on glare ice, but it can be quite useful in emergency situations.

Only 13 models qualified as Top Safety Picks at the start of the 2007 model year. By the end of the model year, though, 23 were named to the Institute's list. A total of 34 models were named to the initial 2008 list, and the two most recent additions were the Cadillac CTS and Infiniti EX35, bringing the total to 36. The complete 2008 list is provided below.-Kirk Bell

Large Cars
Audi A6
Cadillac CTS
Ford Taurus (with optional electronic stability control)
Mercury Sable (with optional electronic stability control)
Volvo S80

Midsize Cars
Audi A3
Audi A4
Honda Accord Sedan
Saab 9-3
Subaru Legacy (with optional electronic stability control)

Midsize Convertibles
Saab 9-3
Volvo C70

Small Cars
Subaru Impreza (with optional electronic stability control)

Honda Odyssey
Hyundai Entourage
Kia Sedona

Midsize SUVs
Acura MDX
Acura RDX
Ford Edge
Ford Taurus X
Honda Pilot
Hyundai Santa Fe
Hyundai Veracruz (built after August 2007)
Infiniti EX35
Lincoln MKX
Mercedes-Benz M-Class (built after December 2007)
Subaru Tribeca
Toyota Highlander
Volvo XC90

Small SUVs
Honda CR-V
Honda Element
Subaru Forester (with optional electronic stability control)

Large Pickups
Toyota Tundra

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