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IIHS News | December 14, 2000Subscribe

Impressive crash test performance for vehicles with side airbags that protect occupants' heads

ARLINGTON, Va. — Many new cars, including not only luxury models but also some popular and less expensive cars, are being equipped with airbags designed to protect people's heads in side impacts. New Insurance Institute for Highway Safety crash tests of the BMW X5 and Volvo S80 — car-into-pole tests and vehicle-to-vehicle tests — demonstrate the important benefits afforded to occupants by these side airbag head protection systems.

Pickup truck into side of Volvo S80

The Institute conducted two crash tests in which the fronts of Chevrolet pickup trucks struck the sides of 1999 Volvo S80s. The S80 in one test included side airbag head protection, while in the other test the S80 did not (both S80s had side airbags for torso protection). In each test, the pickup was going 32 mph, the S80 16 mph. Results show the head airbags provide very important protection in addition to what is afforded by the torso bags.

In the test without the head protection airbag, the heads of the driver and rear passenger dummies were struck by the hood of the pickup truck. The forces recorded on the rear-seat dummy's head were high — in fact, sufficient to cause fatal head injuries. The driver dummy's head contact didn't produce high forces, but the fact that the contact occurred means the head barely escaped severe impact. In contrast, in the test with the head protection airbag both dummies recorded low head forces because the inflatable curtain provided a cushion between the dummies' heads and the hood of the pickup truck.

Injury measures taken from the dummies' torsos were similar in the two Volvo S80s, with and without head protection. In both cars, these measures were low except for abdomen compression on the rear-seat dummies, which were at levels at which a person could sustain serious, though survivable, injuries to the spleen, kidney, or colon.

Pickup into Volvo test

Crash test results: pickup (32 mph) into Volvo S80 (16 mph)
with and without side airbag head protection

  Injury reference value Driver Rear passenger Driver Rear passenger
Head injury criterion 700 140 561 167 1868
Neck compression (kN) -4.0 -0.49 -0.12 -0.39 -0.17
Neck tension (kN) 3.3 0.8 1.4 1.6 2.6
Thoracic trauma index (g) 85 56 75 66 67
Abdomen compression (mm) 39 46 46
Lateral pelvic acceleration (g) 130 70 47 79 49
Bold: value exceeds threshold, indicated by injury reference, above which serious injuries are increasingly likely

Note: Driver dummies are SID H3s, a modified version of the dummy (SID) specified in Federal Motor Vehicle Safety Standard 214 (side impact); the head and neck of the SID H3 are from Hybrid III dummies used in frontal crash testing. Rear-seat dummies used in the above tests are BioSIDs, which are more advanced side impact dummies compared with SIDs; in particular, BioSIDs are designed specifically to measure both acceleration and compression of the chest and abdomen, while SIDs measure acceleration.

“These crash tests demonstrate that head airbags can make very serious vehicle-to-vehicle side impacts survivable by preventing the intruding vehicle structure from striking occupants’ heads. Without head airbags, serious or fatal head injuries become more likely," says Institute president Brian O'Neill.

Car-into-pole crash tests

The Institute also conducted side-into-pole crash tests of a BMW X5 and Volvo S80, both equipped with side airbag head protection — an inflatable curtain in the Volvo and an inflatable tube-shaped airbag in the BMW. In each test, the vehicle was propelled sideways at 18 mph into a rigid pole.

BMW X5 pole test

2001 BMW X5 with side airbag head protection system:
crash test results, 18 mph into pole

  Injury reference value Test result
Head injury criterion 700 439
Neck compression (kN) -4.0 -0.47
Neck tension (kN) 3.3 1.5
Thoracic trauma index (g) 85 51
Abdomen compression (mm)
Lateral pelvic acceleration (g) 130 43
Note: test dummy (SID H3) doesn't record abdomen compression.

1999 Volvo S80 with side airbag head protection system:
crash test results, 18 mph into pole

  Injury reference value Test result
Head injury criterion 700 265
Neck compression (kN) -4.0 -0.16
Neck tension (kN) 3.3 1.0
Thoracic trauma index (g) 85 37
Abdomen compression (mm)
Lateral pelvic acceleration (g) 130 43
Note: test dummy (SID H3) doesn't record abdomen compression.

The 18 mph speed of this test "might not sound like one at which a crash could be serious," O'Neill says, "but impacts into rigid objects such as poles or trees at 18 mph are, in fact, very severe." The intrusion into the X5 and S80 indicates the severity. The pole is relatively narrow, so there was major penetration into the side of each car. Yet the forces recorded on the dummies' heads in these tests were low.

"These tests demonstrate that people can survive serious side impact crashes in the real world because head airbags prevent their heads from striking rigid objects," O'Neill says. He adds that "side airbags with head protection represent a very important safety development that will save lives and prevent major head trauma in a range of serious side impact crashes."

All four crash tests involving Volvos and a BMW were conducted in cooperation with the vehicle manufacturers.

How big a problem are side impacts?

Almost 10,000 occupant deaths occur each year in side impact crashes, and more than half of these deaths involve head injuries. Head injuries are the cause of death in 51-74 percent of single-vehicle side impacts and 41-64 percent of multiple-vehicle side impacts (source: NASS/CDS, 1995-99).

Passenger vehicle occupant deaths in side impact crashes

Crash type Single-vehicle Multiple-vehicle Total
All 14,733 17,210 31,943
Side impact 2,957 6,700 9,657
Side impact with fatal head injury 1,500-2,200 2,700-4,300 4,200-6,500
Source: Fatality Analysis Reporting System, U.S. Department of Transportation, 1999

Thirty-eight percent of single-vehicle side impact crash deaths occur when vehicles strike trees or poles on the dead occupants' side of the vehicle. In two-vehicle side impact crashes, 38 percent of car occupant deaths occur when a pickup or sport SUV strikes the car (source: Fatality Analysis Reporting System, 1999).

Side airbag head protection systems in 2001 models

The designs of side airbag head protection systems in BMWs and Volvos aren't the same. The BMW design is a tubular structure that inflates from the roof to protect occupants' heads. Volvo's side airbags are curtain designs that deploy from the roof. Other side airbags in 2001 models deploy from the vehicle seat, inflating forward and upward to cushion occupants' heads and chests.

"These new cars are being equipped with side airbags with head protection in the absence of any government requirement to do so. It's the market that's driving many of the important advances today," O'Neill says.

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