Side impact crash testing/ratings criteria

NOTE: When side airbags are optional, the Institute tests without the option and will conduct a second test with the optional airbags if the manufacturer requests it and reimburses the Institute for the cost of the vehicle.

Today's passenger vehicles are more crashworthy than they used to be, especially in frontal crashes. As occupant protection in frontal crashes improves, the relative importance of protection in side impacts increases. From the early 1980s until 2000, driver death rates per million cars registered decreased 47 percent. Most of this improvement was in frontal crashes, in which driver death rates decreased 52 percent. In contrast, the decrease in side impacts was only 24 percent.

In crashes with another passenger vehicle, 51 percent of driver deaths in recent model cars during 2000-01 occurred in side impacts, up from 31 percent in 1980-81. During the same time, the proportion of deaths in frontal impacts declined from 61 percent to 43 percent.

These changes are attributable to two effects. There have been significant improvements in frontal crash protection — standard airbags, improved structural designs, and higher belt use rates, for example. At the same time, growing sales of SUVs and pickups have exacerbated height mismatches among passenger vehicles, thereby increasing the risks to occupants of many vehicles struck in the side. In crashes between cars and other passenger vehicles during 2000-01, almost 60 percent of the driver deaths in the cars struck on the driver side were hit by SUVs or pickups — up from about 30 percent during 1980-81.

Since 1997 the federal New Car Assessment Program, which compares crashworthiness among new passenger vehicles, has included side impacts. In these tests, an impactor with a deformable front end representing the front of a car is used to strike the sides of the vehicles being assessed. This moving deformable barrier was developed in the early 1980s, when cars represented most of the vehicles on the road. The height of the barrier's front end is below the heads of the dummies that measure injury risks in the side-struck vehicles. These federal tests don't assess the risks of head injury from impacts with vehicles like SUVs and pickups.

The changed vehicle mix and high risks to occupants of side-struck vehicles when the striking vehicles are SUVs or pickups led the Institute to modify the moving deformable barrier used in the federal test so the front end represents the geometry of a typical SUV or pickup. The result is a barrier that's higher off the ground, taller, and contoured.

Before initiating this side impact crashworthiness evaluation program in 2003, the Institute conducted extensive developmental tests. These included tests comparing the results from side impacts with barriers versus side impacts with SUVs or pickups.

The test configuration resulting from this research is a 31 mph (50 km/h) perpendicular impact into the driver side of a passenger vehicle. The moving deformable barrier that strikes the test vehicle weighs 3,300 pounds (1,500 kg) and has a front end shaped to simulate the typical front end of a pickup or SUV. In each side-struck vehicle are two instrumented SID-IIs dummies representing a small (5th percentile) female or a 12-year-old adolescent. These dummies are positioned in the driver seat and the rear seat behind the driver.

This is the first US consumer information test program to use a dummy that represents small females. There are two reasons for this choice. One is that data from serious real-world side impacts indicate that women are more likely than men to suffer serious head injuries. The other reason is that the head of the smaller SID-IIs driver dummy is in the window area where people's heads are more vulnerable to being struck by the front end of a striking vehicle in a real-world side impact.

The Institute's side impact test is severe. Given the designs of today's vehicles, it's unlikely that people in real-world crashes as severe as this test would emerge uninjured. But with good side impact protection, people should be able to survive crashes of this severity without serious injuries.

NOTE: Side impact crash test ratings can be compared across vehicle type and weight categories, while frontal crash test ratings cannot. This is because the kinetic energy involved in the side impact test depends on the weight and speed of the moving barrier, which are the same in every test. In contrast, the kinetic energy involved in the frontal crash test depends on the speed and weight of the test vehicle.

Ratings criteria

Overall evaluation (side): The three factors evaluated in the Institute's side impact test — driver and passenger injury measures, head protection, and structural performance — determine each vehicle's overall side crashworthiness evaluation. The order in which vehicles are listed depends on performance in frontal offset crash tests as well as side impact tests. Ideally vehicles should be good performers in both test configurations — a double good. Head restraint and bumper evaluations influence the rankings of vehicles with otherwise similar overall crashworthiness performance.

Injury measures: Obtained from two SID-IIs dummies, one in the driver seat and the other in the rear seat behind the driver, injury measures are used to determine the likelihood that a driver and/or passenger would have sustained significant injury to various body regions. Measures are recorded from the head, neck, chest, abdomen, pelvis, and femur. These injury measures, especially from the head/neck and torso (chest and abdomen), are major components of each vehicle's overall evaluation.

Head protection: To supplement head injury measures, the movements and contacts of the dummies' heads during the crash are evaluated. This assessment is more important for seating positions without head protection airbags, which (assuming they perform as intended) should prevent injurious head contacts. Very high head injury measures typically are recorded when the moving deformable barrier hits the dummy's head during impact. However, a "near miss" or a grazing contact also indicates a potential risk of serious injury in a real-world crash. This is because small differences in occupants' heights or in their seating positions compared with the test dummies could result in a hard contact and high risk of serious head injury. In the rear seat, the potential for serious injury is influenced by whether the seating position puts occupants' heads in proximity to areas designed with padding or something else to reduce impact forces versus areas with hard or unprotected structures. Analysis of the movement and contact points of the dummies' heads during the side impact crash test is used to assess this aspect of protection.

Structure/safety cage: Structural performance is based on measurements indicating the amount of intrusion into the occupant compartment around the B-pillar (between the doors). This assessment indicates how well a vehicles side structure resisted intrusion into the driver and rear-seat passenger space. Some intrusion into the occupant compartment is inevitable in serious side impacts. Any intrusion that does occur should be uniform both horizontally and vertically and shouldn't seriously compromise the driver and passenger space. Less intrusion helps assure that other occupants of sizes and in seating positions different from the dummies also would have lower injury risk.

Test verification

Verification ratings are based on 31 mph side crash tests conducted by manufacturers for vehicles meeting requirements established by the Institute. Manufacturers supply information on basic vehicle and test parameters, measurements of B-pillar intrusion into the occupant compartment, injury data recorded on dummies representing small females in the driver and rear passenger seats, and video of the tests. Institute engineers review this information and rate vehicles based on the same evaluation parameters used for the Institute's side test. To ensure manufacturers' good faith participation, the Institute conducts audit tests.

Only redesigned vehicles with immediate predecessors that earned the top rating of good in previous Institute tests are eligible for verification ratings. Substantially redesigned vehicles with significant changes in size, weight, or body style aren't eligible. The Institute will continue to test these vehicles.

Verification assures that automakers still pay attention to side crash protection as they redesign their vehicles and introduce new ones. This approach is possible because of manufacturers' actions since we introduced the side crash test program. They have incorporated side crash test performance plus government-required and other consumer information crash testing into their guidelines. They routinely conduct their own side tests during the design process. In recognition of this, the verification approach goes a step beyond an Institute policy in place since the beginning of the side test program. Manufacturers always have been asked to confirm whether the Institute's ratings could be carried over from one model year to the next. Based on this information, the Institute has been carrying over ratings for vehicles with no significant design changes.

When the Institute began evaluating side crashworthiness by vehicle group beginning in 2003, only about 1 of 5 vehicles tested earned good ratings. Nearly all of the others were rated poor. Since then, the Institute’s side tests have prompted huge improvements in occupant protection in side impacts. Manufacturers have responded to this testing program by changing the designs of their vehicles to improve side crashworthiness and equipping their vehicles with side airbags. Now most current passenger vehicle designs with side airbags earn good ratings based on Institute tests.

The Institute's test primarily assesses how well a vehicle's side structure prevents intrusion into the occupant compartment, or safety cage and, for vehicles with side airbags, how well the head, torso, and pelvis are protected by the airbags. If the occupant space remains largely intact, then the side impact restraint systems can control the motion of the crash test dummy and help keep injury measures low. But if there's significant deformation of the safety cage and intrusion into the compartment, then the restraint systems are less likely to keep the measures low. Newer vehicles have much stronger occupant compartments, in large part because of the steps automakers have taken to earn good ratings in the Institute's side crash tests, and side airbags have become standard equipment in most passenger vehicles since these tests began. Side crash test verification will ensure these gains are maintained.

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2009	2010	2012