Friday, 30 June 2006 17:00

Large cars rated poor for side impact lack side air bags

The redesigned Chevrolet Impala and Toyota Avalon, both equipped with standard side air bags, earn top ratings of good in side crash tests that simulate an impact from an SUV or pickup truck. The Insurance Institute for Highway Safety (Institute) recently conducted side tests of eight large family cars. The Buick Lucerne and Hyundai Azera, also equipped with standard side air bags, earn the second highest rating of acceptable. 

The Buick LaCrosse with standard side air bags is rated marginal, and so is the Chrysler 300 equipped with optional side air bags. The 300, Ford Five Hundred, and Ford Crown Victoria, all tested without their optional side air bags, are rated poor for side impact protection.

The Ford Five Hundred with optional side air bags was tested last year and earned a good rating. With optional side air bags, the Five Hundred and its twin Mercury Montego earn the Institute's Top Safety Pick 2006 (gold) award for good ratings in front, side, and rear tests. According to Ford, the Five Hundred and Montego will be equipped with standard side air bags beginning with cars built in September 2006.

Side impacts are the second most common fatal crash type after frontal crashes. About 9,700 people were killed in side impacts in 2004. In crashes involving newer model cars in collisions with other passenger vehicles, more driver deaths now occur in cars struck in the side (51 percent) than in the front (44 percent). This contrasts with the past when more deaths occurred in frontal crashes.

"The change reflects the big improvements manufacturers have made in frontal crashworthiness in response to Institute and federal government frontal crash test programs," says Institute president Adrian Lund. "These new crash test results show that the same improvements are beginning to be made for protection in serious side impacts."

Impala, Avalon are star performers

The side structures of these two cars performed reasonably well in resisting intrusion from the striking barrier during the crash test. Both cars are equipped with standard curtain-style side air bags designed to protect the heads of people in both front and rear seats.

In the test of the Impala, intrusion into the occupant compartment was minimized by the strong pillar between the front and back doors. The side air bags deployed from above the window frames and inflated between the heads of the crash test dummies and the intruding barrier.

"This is why side air bags with head protection are critical," Lund points out. "Without them, people's heads are vulnerable to being struck by the front ends of striking vehicles or trees and poles."

Both the Impala and Avalon earn acceptable ratings for side structure. Nearly all injury measures on heads, chests, and other body areas of the test dummies were low.

Side air bags are standard in more cars

Growing sales of SUVs and pickup trucks have exacerbated height mismatches among passenger vehicles, and these mismatches increase the risk of serious head injuries among occupants of side-struck vehicles. SUVs and pickups made up 31 percent of new vehicle sales in 1994, but the proportion had increased to nearly 47 percent by 2004.

When the Institute began its side impact test program in 2003, simulating an impact in which a vehicle is struck by a pickup or SUV, few of the vehicles that were tested had head-protecting side air bags as standard equipment. This has improved so that such air bags are standard in half of the large family car models the Institute recently tested.

"Manufacturers are responding to this test in two significant ways," Lund explains. "They're beefing up the designs of their vehicles' side structures, and they're adding side air bags with head protection to more vehicles as standard equipment."


Side air bags with head protection became standard in 2005 Avalons, 2006 Impala and LaCrosse models, and in the Lucerne when it was introduced to replace the LeSabre and Park Avenue models in 2006. The predecessor to the Azera, the Hyundai XG350, had standard combination head/chest side air bags for front-seat occupants. The replacement Azera was upgraded in 2006 with standard curtain-style air bags as well as chest air bags that protect both front-and rear-seat occupants.

Side air bags once were exclusively found in luxury models, but now they're increasingly standard even in inexpensive cars. Overall nearly 40 percent of 2006 passenger vehicle models have standard side air bags with head protection. In contrast, only 23 percent of 2003s did.

Side air bags aren't mandated by the federal government like frontal air bags have been since the 1990s. However, manufacturers have voluntarily agreed to make side air bags standard in all vehicles by the 2009 model year.

"The market is demanding them," Lund says.

Worst performers lack side air bags

All three cars that earned the lowest rating of poor, Chrysler 300 plus Ford Five Hundred and Crown Victoria, were tested without their optional side air bags. In the Five Hundred, the driver dummy's head was hit by the intruding barrier. This produced high head injury measures. In a real-world crash of similar severity, the driver could have sustained a serious skull fracture and brain injuries. Rib fractures and internal organ injuries also would be possible.

The driver dummy's head was struck by the barrier in the 300 without side air bags, although this did not produce high head injury measures. Equipped with its optional side air bags, the 300 improved to marginal and head protection was good. However, injury measures from the dummy's pelvis and chest kept this car from earning a higher overall rating.

The Crown Victoria without side air bags is rated poor. It earned the worst structural rating in this group of large cars. Although the driver dummy's head was not struck by the intruding barrier, a high acceleration occurred when the head struck the window sill. High forces were recorded on the driver dummy's chest, indicating the likelihood of rib fractures and internal organ injuries.

The Crown Victoria is available with optional combination head/torso side air bags for front-seat occupants. Ford is making design changes to improve this car's protection of occupants in side impacts and has asked the Institute to test a Crown Victoria with its optional side air bags. When the changes are made, the Institute will conduct the test and report the results.

The side impact test is only one measurement of vehicle crashworthiness. The Institute also conducts 40 mph frontal offset crash tests and evaluates vehicles' seat/head restraint designs for protection in rear crashes. All of the cars in this group except the Impala earned the highest rating of good in the frontal offset test. The Impala is rated acceptable. The seat/head restraints in all but three of the cars in this group also have been rated for rear crash protection.

Nearly every passenger vehicle now earns a good rating in the Institute's frontal crash test, but performance varies widely in side and rear tests. These differences can help consumers choose vehicles that offer the best overall crash protection.

How the side impact test is conducted

A vehicle's side evaluation is based on performance in a crash test in which the side of the vehicle is struck by a barrier moving at 31 mph. The barrier represents the front end of a pickup or SUV.

Overall ratings reflect injury measures recorded on two instrumented SID-IIs dummies, assessment of head protection countermeasures, and the vehicle's structural performance during the test. Injury measures obtained from the two dummies, one in the driver seat and the other in the rear seat behind the driver, are used to determine the likelihood that a driver and/or passenger in a real-world crash would sustain serious injury to various body regions. The movements and contacts of the dummies' heads during the test also are evaluated.

Structural performance is based on measurements indicating the amount of B-pillar intrusion into the occupant compartment.


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