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2021 VW ID. 4 side-impact crash test IIHS A Volkswagen ID.4 EV is subjected to IIHS’s side-crash test. The ID.4 received a “good” score for the test, the agency’s highest mark, and a Top Safety Pick+ rating overall. | Photo courtesy IIHS

Automobiles provide us with tremendous benefits, arguably the greatest being freedom of movement. But cars also present their own unique set of challenges, not the least of which is causing death and injury to tens of thousands of drivers, passengers, pedestrians, and cyclists annually in the U.S., to say nothing of the associated billions of dollars in health-care costs, lost wages, and property damage.

The first motor-vehicle fatality was recorded in New York City in 1899. Casualties increased apace throughout the 20th century, and by 1965, car crashes had become the leading cause of death for Americans under age 44. Vehicle-related deaths crested at 54,589 in 1972; since then, crash-related deaths have declined, averaging about 35,000 per year since 2008.

Despite this reduction, however, “death and injuries from traffic crashes continue to be among the most serious health-related problems facing our country,” states the National Highway Traffic Safety Administration (NHTSA).

Building safer cars

Reducing the number of deaths and injuries from car crashes can be achieved in 2 basic ways: first, by making vehicles safer, and second, by changing a society’s traffic-safety culture—the beliefs, values, and behaviors regarding driving and traffic safety.

In part because changing traffic-safety culture is so difficult, the U.S. has focused its safety efforts mainly on vehicle crash testing and developing vehicle safety features, such as automatic emergency braking.

Advanced driver-assistance systems (ADAS) have been getting a lot of media attention of late, but having a full complement of safety features is pointless if a vehicle’s basic structure isn’t sound. That can be assessed by subjecting it to various types of crashes.

Two organizations crash test new vehicles and publish their findings: the aforementioned NHTSA (pronounced nit-sa) and the Insurance Institute for Highway Safety (IIHS), an independent safety-research group funded by auto insurers.

Both agencies test cars under controlled conditions that simulate real-world car crashes. Then, based on the results, NHTSA and IIHS rate how well a vehicle is likely to protect its occupants in specific types of crashes. Largely as a result of NHTSA and IIHS testing, vehicle safety has improved dramatically over the past several decades.

NHTSA crash testing

NHTSA began crash testing cars in 1973 and has continually improved its testing programs, making standards more comprehensive and stringent. NHTSA performs 3 types of crash tests that encompass the majority of crashes on America’s roadways: a frontal test and 2 side tests. They also do a rollover test. Seat-belted dummies are placed inside crash-tested vehicles, and sensors on the dummies record injuries to various body parts.

Star ratings (1 through 5, with 5 being best) designate a vehicle’s safety rating in each of these areas; each vehicle also gets an overall star rating. The higher the number of stars a vehicle receives for a given test, the lower the chance of occupant injury in that type of collision. (“More stars mean safer cars,” goes the NHTSA slogan.)

Frontal testing

Frontal crashes are the crashes most likely to result in fatalities. In NHTSA’s frontal test, a vehicle accelerates straight into a rigid barrier at 35 mph; the entire width of the vehicle strikes the barrier.

Side testing

NHTSA’s side-barrier crash test simulates being “T-boned” on the driver’s side at an intersection. In the test, a 3,015-pound moving barrier crashes into the side of a standing vehicle at 38.5 mph.

Side Pole Crash

An Audi Q7 SUV following NHTSA’s side-pole crash test. The Q7 received the highest rating, 5 stars, for the test and 5 stars as an overall rating. | Photo courtesy Audi

The agency’s side-pole crash test simulates a driver losing control of a vehicle, sliding, and crashing into a telephone pole, tree, or similar object on the driver’s side. A vehicle, angled at 75 degrees, is pulled sideways at 20 mph into a pole at the driver’s seating location.

Rollover resistance ratings

Deaths from rollovers account for about 18% of all vehicle-crash fatalities. NHTSA’s rollover resistance rating is based on a measurement known as the static stability factor, which determines how top-heavy a vehicle is. In addition, vehicles are subjected to a severe driving movement that tests a vehicle’s vulnerability to tipping over.

NHTSA gives vehicles with certain advanced safety features extra credit. Based on its performance testing, NHTSA recommends that consumers purchase vehicles with forward-collision warning, automatic emergency braking, and lane-departure warning.

NHTSA has also created a shopping guide to make today’s driver-assistance technologies easier to understand. 

In the future, NHTSA’s plans include recommending 4 types of driver-assistance technologies; updating its crash-test procedures; reviewing emerging technologies related to driver distraction, alcohol detection, intelligent speed assist, and driver-monitoring systems; and providing a crash-avoidance rating on new-car window stickers.

To find out the safety ratings for specific vehicles, go to the ratings section on the NHTSA website.

IIHS crash testing

The Insurance Institute for Highway Safety began evaluating vehicle crashworthiness in 1995. Its crash testing is similar and complementary to NHTSA’s testing, and the agency continually refines and improves its test procedures.

IIHS runs 3 frontal crash tests, a side test, a roof-strength test, and a test of head restraints and seats. It also track-tests forward-collision warning and automatic emergency braking systems, and evaluates headlight systems and child–seat attachment hardware.

IIHS gives cars “good,” “acceptable,” “marginal,” or “poor” ratings on crash-related and headlight evaluations, and “superior,” “advanced,” or “basic” ratings for tests of front-crash prevention systems. Additionally, IIHS awards Top Safety Pick and Top Safety Pick+ designations to vehicles that perform best in the agency’s crashworthiness, crash-avoidance, and crash-mitigation tests.

Frontal testing

The 3 IIHS frontal crash tests are moderate-overlap front, driver-side small overlap front, and passenger-side small overlap front. Depending on the test, various types of test dummies are belted inside the vehicles.

Moderate-Overlap Front Crash

Volvo’s XC40 Recharge EV undergoes IIHS’s moderate-overlap front-crash test. The XC40 received a “good” rating for this test and was awarded a Top Safety Pick+ by the agency. | Photo courtesy Volvo

In the moderate-overlap front test, a vehicle travels at 40 mph toward a barrier. Only 40% of the vehicle width on the driver side strikes the barrier. Because it’s not the full width, a smaller part of the structure has to manage the crash energy, and intrusion of vehicle parts into the passenger compartment is more likely.

Driver Side Small-Overlap Crash

A post-crash view of a Hyundai Ioniq 5 EV after a driver-side small-overlap front-crash test. Note that no part of the vehicle intruded into the area around the dummy’s legs. The Ioniq 5 received a “good” test rating and a Top Safety Pick+ award. | Photo courtesy Hyundai

In 2012, IIHS introduced a driver-side small-overlap frontal crash test, where a vehicle travels at 40 mph toward a rigid barrier. Only 25% of the vehicle width on the driver side strikes the barrier.

Small-overlap front crashes mainly affect a vehicle’s outer edges, which aren’t well protected by its crush zones, and a front wheel may be forced rearward into the footwell, resulting in serious leg and foot injuries.

IIHS began performing a passenger-side small-overlap frontal test in 2017—the same as the driver-side test, except that the vehicle overlaps the barrier on the right side.

Side testing

Side crashes account for about 25% of vehicle-occupant deaths. In the IIHS side-crash test, which became more rigorous in 2021, a 4,200-pound barrier the height of an SUV hits the driver side of a standing vehicle at 37 mph.

Roof-strength tests

Roof strength is determined by pushing an angled metal plate down on one side of the roof at a slow, constant speed and measuring the force required to crush the roof.

Head restraints and seat testing

IIHS tests vehicle front seats and head restraints with a special dummy that has a realistic spine. The vehicle seat, with the dummy in it, is placed on a sled, which is moved to simulate a rear impact.

Advanced safety systems

IIHS also track-tests 2 advanced safety features: forward-collision warning and automatic emergency braking. The testing assesses both vehicle-to-vehicle and pedestrian front-crash protection.

Future changes to the IIHS test program include updating the moderate overlap test, which will focus on improving occupant protection in the backseat, and nighttime pedestrian front-crash prevention tests. The new tests will include low-light situations, which are more challenging for ADAS technology.

Car crashes in the real world

Crash tests in a laboratory are all well and good, but do good test ratings translate to lives saved in the real world?

In a word, yes. IIHS analyzed more than a decade’s worth of crash data and found that a driver of a vehicle rated “good” in the moderate overlap test is 46% less likely to die in a frontal crash compared with a driver of a vehicle rated “poor,” and a driver of a vehicle rated “acceptable” or “marginal” is 33% less likely to die than a driver of a poorly rated one.

Furthermore, regarding side crashes, a driver of a vehicle rated “good” in the original (pre-2021) test is 70% less likely to die in a driver-side crash, compared with a driver of a vehicle rated “poor.” A driver of a vehicle rated “acceptable” is 64% less likely to die, and a driver of a vehicle rated “marginal” is 49% less likely to die.

John Lehrer is the automotive editor of Westways. This article was excerpted and adapted from the AAA Car Guide, available in hard copy at AAA branches.

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