With so many current IIHS “Top Safety Picks”, the Institutes rating system became nothing more than advertising sound bites. This will soon change.
Wayne Gerdes -
CleanMPG - Aug. 14, 2012
Latest Insurance Institute for Highway Safety (IIHS) small overlap frontal crash test gets seriously tough with < 30 percent of midsize cars evaluated earning a good or even acceptable rating.
Case Studies
According to the IIHS PR, the 2012 Acura TL and Volvo S60 continue to earn good ratings while the 2012 Infiniti G earns acceptable. The 2012 Acura TSX, BMW 3 series, Lincoln MKZ and Volkswagen CC earn marginal ratings. The 2012 Mercedes-Benz C-Class, Lexus IS 250/350, Audi A4 and Lexus ES 350 earn poor.
The new test has 25 percent of a car's front end on the driver side strike a 5-foot-tall rigid barrier at 40 mph with a 50th percentile male belted in the driver seat. The test is designed to replicate the front corner of a car colliding with another vehicle or an object like a tree or utility pole. Outside of some automakers' proving grounds, such a test isn't currently conducted anywhere in the United States, Europe or possibly even Asia.
Current Status Quo
The number of drivers of 3-year-old or newer passenger vehicles involved in fatal frontal crashes has fallen 55 percent since 2001. Much of the improved outlook is due to the success of crash testing like the New Car Assessment Program (NCAP) begun by the National Highway Traffic Safety Administration (NHTSA) in 1978 and crashworthiness evaluations the Institute started in 1995. In NHTSA's frontal test, passenger vehicles crash at 35 mph into a rigid barrier covering the full width of the vehicle. In the Institute's 40 mph offset frontal test, currently called a moderate overlap frontal test, 40 percent of the total width of a vehicle strikes a deformable barrier on the driver side.
In a 2009 Institute study of vehicles with good ratings for frontal crash protection,
small overlap crashes accounted for nearly a quarter of the frontal crashes involving serious or fatal injury to front seat occupants. Another 24 percent of the frontal crashes were moderate overlap crashes, although they likely occurred at much higher speeds than the Institute's moderate overlap test. An additional 14 percent occurred when passenger vehicles underrode large trucks, SUVs or other high-riding passenger vehicles. The Institute is exploring countermeasures for large truck underride crashes and in other research has found that the problem of crash incompatibility between cars and SUVs is being reduced.
The Acura TL earns a good rating in the small overlap frontal test. The driver space was maintained reasonably well, and the dummy's movement was well controlled. Measures taken from the dummy indicate a low risk of any significant injuries in a crash of this severity. The test is designed to replicate what happens when the front corner of a vehicle collides with another vehicle or an object like a tree or utility pole.
Structural Integrity
The key to protection in any crash is a strong safety cage that resists deformation to maintain survival space for occupants. Then vehicle restraint systems can do their jobs to cushion and protect people.
Most modern cars have safety cages built to withstand head-on collisions and moderate overlap frontal crashes with little deformation. At the same time, crush zones help manage crash energy to reduce forces on the occupant compartment. The main crush-zone structures are concentrated in the middle 50 percent of the front end. When a crash involves these structures, the occupant compartment is protected from intrusion, and front airbags and safety belts can effectively restrain and protect occupants.
Small overlap crashes are a different story. These crashes primarily affect a car's outer edges, which aren't well protected by the crush-zone structures. Crash forces go directly into the front wheel, suspension system and firewall. It is not uncommon for the wheel to be forced rearward into the footwell, contributing to even more intrusion in the occupant compartment and resulting in serious leg and foot injuries. To provide effective protection in small overlap crashes, the safety cage needs to resist crash forces that aren't tempered by crush-zone structures. Widening these front-end structures also would help.
Most automakers design their vehicles to ace the IIHS moderate overlap frontal test and the NHTSA's full-width frontal test whereas the problem of small overlap crashes is not addressed. The new revolutionary IIHS small overlap crash test changes all of that.
New IIHS small overlap crash test result details
The IIHS PR stated that vehicle test performance varied widely in the three rating categories: structure, restraints and kinematics, and dummy injury measures. The
majority of the cars had lots of occupant compartment intrusion, which contributed to their low overall rating. Occupant motion varied greatly as well, with the dummy missing the airbag in some cases. In others, safety belts allowed the dummy's head and torso to move too far forward toward the A-pillar. Forces measured on the dummy indicated high risk of injury for the legs and feet in several vehicles.
Volvo’s S60 kicks @$$
Structurally, the Volvo S60 was judged to be the best. With only a few inches of intrusion, the occupant compartment looked much the same as it did in a moderate overlap test. Reinforcement of the S60's upper rails and a steel cross member below the instrument panel helped to keep the safety cage intact. Volvo has performed similar small overlap tests as part of its vehicle safety development process since the late 1980s, taking the results into account when designing new models.
LEFT: Survival space for the driver wasn't well maintained in the Lexus IS crash test. The A-pillar bent and the footwell collapsed as the left front wheel and tire were forced rearward. The dummy's feet were entrapped by intruding structures.
RIGHT: Results for the Volvo S60 were very different. The S60's occupant compartment held up well, with only minor intrusion.
The Lexus IS had up to 10 times as much occupant compartment intrusion as the Volvo. In the IS test, the car's A-pillar bent and the footwell collapsed as the left front wheel and tire were forced rearward. The dummy's left foot was entrapped by intruding structure, and its right foot was wedged beneath the brake pedal. Entrapment also was an issue with the Mercedes C-Class. The dummy's right foot ended up wedged beneath the brake pedal as the left front wheel was forced rearward during the crash.
When the Volkswagen CC was put to the test, the driver door was sheared off its hinges. The CC is the first vehicle the Institute has ever evaluated to completely lose its door. An open door results in an automatic downgrade to poor for restraints and kinematics, as also was the case with the Audi A4, whose door opened but remained attached to the car. Doors should stay closed in a crash to keep people from being partially or completely ejected from vehicles.
Restraint systems' key role
Safety belts and airbags are important in any crash configuration, and they are especially taxed in small overlap frontal crashes. When cars strike the test barrier they tend to move sideways away from it, and the interior structures including the driver door, side window and A-pillar move in the same direction. The test dummy, however, keeps moving forward into the path of the sideways-moving interior structures. At the same time, the steering column and driver airbag move inboard in many vehicles because of the way the front end and occupant compartment deform. If the dummy misses the airbag or slides off it, the head and chest are unprotected.
Front airbags are calibrated to deploy in these types of crashes. Side airbags, including head-protecting curtains and chest-protecting torso airbags, don't always deploy because they are designed mainly for true side impacts — think so-called T-bone crashes at intersections. When they do deploy, they don't always do so early enough or extend far enough forward to adequately protect people. The result is an airbag gray zone with gaps between what front airbags cover and what side airbags do — if they deploy at all.
Without airbag protection, people in real-world small overlap frontal crashes can sustain head injuries from direct contact with the A-pillar, dashboard or window sill or by hitting trees, poles or other objects. Chest injuries happen when people contact the steering wheel, door or other intruding structures.
Every luxury car and near-luxury car the Institute evaluated earns good ratings for head, neck and chest injury risk based on measurements from the dummy's sensors. This is true even though there are many cases of serious upper body injuries in real-world crashes with similar vehicle damage.
One possible reason for the differing results is that real people move more during a crash and are prone to be out of position at the start, compared with relatively stiff and precisely positioned crash test dummies. Not all drivers are the same size as the dummy or seated exactly the same way. A close call for the dummy could mean an actual injury for a person. In several crash tests, the dummy's head barely missed the intruding structure of the vehicle, where a real person may have made contact and sustained an injury. Another reason is that the frontal crash dummy the Institute uses in the small overlap test is not good at measuring risks from lateral forces. Side crash dummies do a better job of this but can't sense — or record — much of the frontal action in these tests.
Side curtain and torso airbags deployed in the Acura TL and Volvo S60, although the S60's torso airbag fired too late in the crash to protect the dummy's chest from potential contact with side structures. One or both of the curtain and torso airbags didn't deploy in seven of the cars evaluated. Of the six curtains that deployed, four didn't provide sufficient forward coverage. The Institute lowered restraint and kinematics scores if side airbags didn't deploy or coverage was lacking.
In the Lincoln MKZ test, the dummy's head and chest completely missed the front airbag as the steering column moved to the right. The side curtain airbag deployed but didn't extend far enough forward to protect the dummy's head. In comparison, the Acura TL's front and side curtain airbags worked well together to keep the head from coming close to any stiff structures or objects that could cause injury.
LEFT: The dummy's head and chest missed the MKZ's front airbag as the steering column moved to the right. The side curtain airbag didn't have sufficient forward coverage for the head.
RIGHT: In contrast, the TL's front and side curtain airbags did a good job of protecting the dummy's head.
Engineers at some manufacturers have indicated that they are adjusting airbag algorithms to deploy side airbags in small overlap frontal crashes. Mercedes, for example, plans changes for the current C-Class.
Another restraint and kinematics issue Institute engineers flagged was excessive forward movement of the driver dummy caused by too much shoulder belt webbing spooling out of the retractor. This was the case with the BMW, Mercedes and Volkswagen. Like most new vehicles, these cars have safety belts equipped with load limiters that allow occupants' upper bodies to move forward in frontal crashes when belt loads exceed a specific threshold. Load limiters allow some belt spoolout after the initial impact to reduce belt-force-related thoracic injuries such as rib fractures by allowing people to ride down deflating front airbags. However, too much spoolout can compromise belt effectiveness by allowing belted occupants to move enough to strike hard surfaces inside the vehicle. This concern is greater in small overlaps where occupants may load only a small part of the front airbag or miss it completely.
Finally a tougher award criteria
The IIHS Top Safety Pick award recognizes passenger vehicles that do the best job of protecting people in front, side, rollover and rear crashes based on ratings in Institute evaluations. The front rating is based on the moderate overlap test.
The Institute plans to make the top award criteria more stringent by adding the small overlap frontal test to its battery of evaluations. The existing criteria will continue for the 2013 award cycle, but vehicles that excel in the new test will be recognized.
Models meeting the current award criteria still offer outstanding protection in most crashes, and they will continue to earn Top Safety Pick in 2013. However, those vehicles that also do well in the new test will get to claim a higher award level that will be announced later this year.
The Institute has tightened award criteria twice since the first winners were announced for 2006 models. Good rear test results and availability of electronic stability control became a requirement starting with 2007 models, and a good roof strength rating became a deciding factor for 2010 models. Stability control is no longer a separate requirement since all 2012 and later vehicles must have the feature as standard under federal rules.
Automakers have been quick to rise to the occasion whenever the Institute has added a new evaluation to its vehicle test program, and the small overlap test should be no exception.
You can read the entire release at the following:
New crash test aims to drive improvements in protecting people in frontal crashes
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