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Crash test resultsGood performances from 5 of 11 midsize SUVs tested this year; none of 11 is rated poor

ARLINGTON, Va. — Among 11 midsize SUVs with new or modified designs that were crash tested by the Insurance Institute for Highway Safety this year, 5 are rated good: Acura MDX, Ford Explorer/Mercury Mountaineer, Toyota Highlander, Suzuki Grand Vitara XL-7, and Mitsubishi Montero Sport. The MDX and Explorer/Mountaineer also earn the Institute's top designation, "best pick."

"These performances are encouraging," says Institute president Brian O'Neill. "In the past we haven't seen so many vehicles in a group get good ratings, with none rated poor. Vehicle designs are getting better, as this group of SUVs demonstrates. In particular, vehicle structures are getting better. The structural performances of all 11 SUVs in this group are rated good or acceptable. This means the manufacturers are doing a better and better job of designing their vehicles' safety cages and crumple zones."

Two of the 11 midsize SUVs the Institute tested, the Buick Rendezvous and Isuzu Axiom, are rated acceptable. The other four — Chevrolet TrailBlazer (and its twins, Oldsmobile Bravada and GMC Envoy), Jeep Liberty, Isuzu Rodeo (and its twin, the Honda Passport), and Pontiac Aztek — are marginal. None of the 11 SUVs earns the lowest rating (poor).

The evaluations reflect performances in 40 mph frontal offset crash tests into a deformable barrier. Based on the results of these tests, the Institute evaluates crashworthiness, assigning each vehicle an overall rating from good to poor. Results for 8 of the 11 SUVs were released on Sept. 11 and are re-released here along with ratings for the 3 SUVs tested since then — Explorer, Liberty, and Rodeo.

MDX is top performer

In the 40 mph frontal offset test, the 2001 Acura MDX's occupant compartment "held its shape extremely well, and the dummy went squarely into the airbag. This is an example of very good performance," O'Neill says. "The dummy injury measures were all low, indicating that a driver in a similar real-world crash should walk away with nothing worse than minor injuries."

Explorer improves compared with earlier design

The Institute delayed testing the Ford Explorer because structural modifications intended to improve offset crash test performance were added after this completely redesigned SUV was introduced earlier this year. "By the results of our recent test, the changes were successful. The Explorer's structure held together very well," O'Neill says.

The last time the Institute tested an Explorer (a 1996 model), "it was the old design, which we rated acceptable. The space around the driver was maintained reasonably well, but there was a serious problem. The driver door opened during the impact, which is unusual and troubling. In contrast, the new Explorer performed very well and earns the Institute's best pick designation," O'Neill says.

New TrailBlazer is rated marginal but much improved compared with Blazer

The performance of the 2002 TrailBlazer contrasts sharply with that of Chevrolet's older midsize SUV design, the Blazer (which hasn't been discontinued). The Institute tested a 1996 Blazer and rated it poor. There was major collapse of the occupant compartment during the offset test, and high injury measures were recorded on the dummy's head, which hit the bottom of the Blazer's window frame and B-pillar. "The performance of the TrailBlazer is a big improvement compared with the Blazer. It wouldn't take much for the Trailblazer to improve to a rating better than marginal," O'Neill says.

Compared with the Blazer, the TrailBlazer's front structure allowed much less intrusion into the occupant compartment. Lower intrusion measures indicate a vehicle's safety cage is doing what it's supposed to do (keep the occupant compartment intact, with little or no intrusion into the driver's space), and 9 of 10 measures of intrusion and steering wheel movement are dramatically lower (better) for the new TrailBlazer design:

Chevrolet midsize SUVs:
Measures of occupant compartment intrusion (cm), 40 mpg frontal offset crash test
  A-pillar movement rearward Footwell intrusion Brake pedal intrusion Instrument panel movement Steering column movement
left center right footrest left right upward rearward
2002 TrailBlazer
 3 17 22 17 14 26 4 3 3 3
1996 Blazer
18 30 33 32
33 25 20 18 11 9

"The TrailBlazer's occupant compartment held up much better than the Blazer's, but there were problems with the new design," O'Neill notes. "For example, forces on the right lower leg were high, indicating the likelihood of injury."

Structurally modified Montero Sport improves

Another improver is the 2001 Mitsubishi Montero Sport. When the Institute tested a 1999 model (without the structural modifications to the 2001), it earned a poor overall crashworthiness evaluation. The occupant compartment didn't hold up in the offset test, and there was too much movement of the dummy during the crash. Plus the high forces on both legs indicated the likelihood of injury. The 2001 Montero Sport has been structurally modified, now earning a good overall evaluation. The occupant compartment held up well, and the only serious problem in the offset crash test was that moderately high forces were recorded on the dummy's right leg and foot. These improvements are apparent in comparisons of occupant compartment intrusion and steering wheel movement for the old and new designs:

Mitsubishi Montero Sport:
Measures of occupant compartment intrusion (cm), 40 mpg frontal offset crash test
  A-pillar movement rearward Footwell intrusion Brake pedal intrusion Instrument panel movement Steering column movement
left center right footrest left right upward rearward
2001 2 11 10 7 13 12 2 4 3 -1
1999 13 27 28 21 30 25 11 10 10 8

Two tests of Jeep Liberty

This all-new SUV for 2002 was tested twice, and the structural performances were good in both tests. However, the airbag inflated late in the first test because an airbag sensor wire shorted out early in the crash. This led DaimlerChrysler to develop a fix for this problem that shields the wiring, and the manufacturer has initiated a recall. The Institute tested a Liberty with the fix, and the airbag inflated much earlier "so the fix worked," O'Neill points out. "But the forces on the dummy's head were high. As a result, the Liberty only earns a marginal rating despite its good structural performance."

Isuzu fails to improve Rodeo appreciably

The Institute tested the 2002 model Isuzu Rodeo because the manufacturer indicated it had modified the airbag design and believed this would reduce the high head injury measure recorded in the Institute's previous test of a 2000 model Rodeo. But the airbag changes improved this vehicle's crash test performance "only slightly," O'Neill says, "and measures still indicated the possibility of head injury when the dummy's head loaded the airbag."

How the other five SUVs fared in the 40 mph frontal offset test:

  1. The 2001 Toyota Highlander's overall performance was good, although forces on the right leg indicated there could be a risk of lower leg or ankle injury to someone in a crash like this.
  2. The 2001 Suzuki Grand Vitara XL-7's overall performance was good, although forces on the left leg indicated the possibility of lower leg or ankle injury.
  3. The 2002 Buick Rendezvous' overall performance was acceptable. The occupant compartment was maintained reasonably well, but far too much upward movement of the steering wheel and forward pitching of the driver seat compromised control of the dummy during the impact.
  4. The 2002 Isuzu Axiom's overall performance was acceptable. The occupant compartment was maintained well, but there was a possibility of head, leg, and foot injuries.
  5. The 2001 Pontiac Aztek's overall performance was marginal. While the occupant compartment held up reasonably well, the airbag inflated relatively late in the crash. Plus the steering wheel moved upward. The result is that high forces were recorded on the dummy's head.

Since 1996, the Institute has tested a total of 30 midsize SUV designs. Only 1 of the 23 current designs, the Chevrolet Blazer, earns a poor overall crashworthiness evaluation. New designs of the Blazer's twin models (Oldsmobile Bravada and GMC Envoy) now share the same design as the 2002 TrailBlazer, so they are rated marginal overall.

Structural design is key to good performance

The Institute's frontal offset crash test into a deformable barrier is especially demanding of vehicle structure. The driver side hits the barrier, so a relatively small area of the vehicle's front-end structure must manage the crash energy. This means intrusion into the occupant compartment is more likely to occur than in a full-width test.

"Good structural design is the key to good performance in the offset test," O'Neill notes. "If a car's front-end structure absorbs and manages the crash energy so the occupant compartment remains largely intact, with little or no intrusion into the driver's space, then the dummy's movement is likely to be controlled, and injury measures are likely to be low. In contrast, poor structural design means greater likelihood of poor control of the dummy and high injury measures."

Institute and government crash tests complement each other

The Institute's crashworthiness evaluations are based primarily on results of the frontal offset crash test at 40 mph. Each vehicle's overall evaluation is based on three aspects of performance — measurements of occupant compartment intrusion, injury measures from a Hybrid III dummy positioned in the driver seat, and analysis of slow-motion film to assess how well the restraint system controlled dummy movement during the test.

The federal government has been testing new passenger vehicles in 35 mph frontal crash tests since 1978. This New Car Assessment Program has been a major contributor to crashworthiness improvements — in particular, improved restraint systems in new passenger vehicles. The Institute's offset tests, conducted since 1995, involve 40 percent of a vehicle's front end hitting a deformable barrier at 40 mph. This test complements the federal test involving the full width of the front end hitting a rigid barrier. Both tests are contributing to improvements in crashworthiness — in particular improved crumple zones and safety cages.

The same 40 mph offset crash test is used to evaluate new cars by the European Union in cooperation with motor clubs and by an Australian consortium of state governments and motor clubs.

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