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The Institute also evaluated the Toyota Prius hybrid's front, side,
and rear crashworthiness plus the side crashworthiness of three other
vehicle designs — the Mini Cooper (small car) and Dodge Grand Caravan
and Chevrolet Uplander (minivans). Results for these vehicles update
the results for minivan and small car models that were released last
year. Side tests of the Grand Caravan, Uplander, Mini Cooper, and Impreza
were delayed at the request of the vehicle manufacturers, who were making
changes to improve crashworthiness.
Sedona is top-rated minivan: Among the eight
current minivan designs the Institute has rated, the Sedona is the only
one that earns good ratings in all three Institute tests (this vehicle
also will be sold as the 2007 Hyundai Entourage later this spring). The
new Sedona's frontal crash test performance is an improvement compared
with the previous model, which the Institute rated acceptable.
"The Sedona is the best minivan we've tested," says Institute president
Adrian Lund. "Other minivans have earned good front and side ratings,
but they haven't achieved a satisfactory level of rear crash protection.
The Sedona stands out as the first to get a clean sweep of good ratings
across the board."
In the frontal test, the Sedona's structure held up well. There was
little intrusion into the occupant compartment. The dummy's movement
was well controlled, and injury measures were low. In the side test,
curtain-style airbags prevented the heads of driver and rear passenger
dummies from contacting the intruding barrier. The Sedona is one of five
current minivan models with standard side airbags designed to protect
the heads of people in all three rows of seats. For protection in rear
impacts, the Sedona is a standout. Its seat/head restraints protect front-seat
occupants' necks.
"Many manufacturers haven't paid as much attention to occupant protection
in rear crashes, compared with front and side crashes," Lund points out.
"Kia deserves credit for designing the Sedona's seat/head restraints
for protection in one of the most common kinds of commuter traffic crashes."
The Kia is the only minivan the Institute has evaluated that's equipped
with active head restraints. These are designed to move up and toward
the back of the head during a rear impact. As an occupant's torso sinks
into the Kia seat during a rear-end crash, a mechanism in the seatback
is designed to move the head restraint so it's more likely to be in a
good position to catch the head, keeping it and the torso moving together.
The most common kind of injuries reported from crashes are neck injuries,
and these are most likely to occur in rear impacts. Whiplash is the most
serious injury reported in about 2 million insurance claims each year.
Such claims cost at least $8.5 billion annually.
Subaru is a gold standard among small cars: Just as
manufacturers made major improvements in how their vehicles protect people
in frontal crashes, now they're making similar improvements for side
and rear impact protection. Subaru reinforced the pillar behind the rear
passenger door and upgraded the side airbags to standard in the 2006
Impreza. This car also has head restraints that do a better job than
those in other small cars. The Impreza is a good performer in all three
Institute tests (front, side, and rear) and earns the gold Top Safety Pick award. Its results also apply to the Saab 9-2X, which is based on
the Impreza design.
"Subaru was one of the manufacturers that last year asked us to delay
side testing because of vehicle design changes that were in progress,"
Lund says. "It's not uncommon for us to grant such requests as long as
the design changes will be made in production models within a reasonable
time. The goal of our crash test program is to encourage these kinds
of improvements to reduce injury risk in real-world crashes."
Top Safety Pick winners represent an elite fraction of the car market.
Winners of the gold award have earned good ratings in the Institute's
frontal offset and side impact tests, and their seat/head restraints
are rated good for protection against neck injuries in rear impacts.
Awards are by vehicle size because both size and weight influence occupant
protection in serious crashes. Larger, heavier vehicles generally afford
more protection than smaller, lighter ones. The Top Safety Pick award
indicates a better choice for safety within a size class, but a small
car that earns this award doesn't necessarily afford better protection
than a larger car that doesn't.
First Institute test of a hybrid: The Toyota Prius
was a good performer in the frontal crash test and, equipped with optional
side airbags, also good in the side test. But it's rated marginal for
seat/head restraint design, so it isn't a Top Safety Pick. The
movement of the driver dummy was reasonably well controlled during the
frontal test. Although the dummy's head did hit the pillar between the
doors and the roof rail, head accelerations were low. Other injury measures
also were low, and the Prius's structure held up with minimal intrusion
into the occupant compartment.
"The way a hybrid model earns the top rating in the frontal test is
the same way any other car does," Lund says. "Its front structure has
to crush to absorb crash energy, and it has to have a safety cage that
stays intact so the safety belts and airbags can protect the occupants."
The Institute conducted two side tests of the Prius, with and without
its optional head-protecting side airbags. Without the airbags the Prius
earns the lowest rating of poor. The intruding barrier struck the driver
dummy's head. Measures recorded during the crash indicate that a serious
skull fracture and brain injuries would be likely to occur in a real-world
crash of similar severity.
"The result for the Prius with its optional side curtain airbags was
dramatically different," Lund says. "This time the airbag kept the dummy's
head from being struck by the barrier, and injury measures all were low.
These results show the importance of head-protecting side airbags in
reducing the risks for car occupants, especially when their vehicles
are struck in the side by a pickup or SUV."
Another important aspect of crashworthiness is how well seat/head restraints
protect people from whiplash in rear impacts. The ones in the Prius earn
the second lowest rating of marginal. They can be positioned high enough
and close enough to the backs of most people's heads, but good geometry
alone isn't enough to provide adequate protection from whiplash. Seats
and head restraints have to work together to protect the neck, and the
Institute's test indicates that in a real-world crash the seats in the
Prius wouldn't keep the forces on the neck as low as in other vehicles.
When a vehicle is struck in the rear and driven forward, the vehicle
seats accelerate the occupants' torsos forward. Unsupported, their heads
will lag behind the forward movement of their torsos. This differential
motion causes the neck to bend back and stretch. The higher the torso
acceleration the more sudden the motion, the higher the forces on the
neck, and the more likely a neck injury is to occur.
"If a seat is too stiff, without enough 'give' to it so a person sinks
into it during a crash, then the head restraint can move back and away
from the head. This can lead to higher forces on the neck, and whiplash
injury is more likely," Lund notes.
For most vehicles with hybrid variants, the Institute's ratings apply
to both the hybrid and conventional versions. These vehicles include
the Honda Civic and Accord, Lexus RX, and Toyota Highlander. The Prius
is sold only as a hybrid.
Uplander minivan is poor performer in side test: The
Institute tested the Chevrolet Uplander with and without its optional
side airbags (results apply to similar Buick, Pontiac, and Saturn models).
In both tests there were problems with the seats in the middle row. With
the optional side airbags, all four attachment points for the seat occupied
by the rear passenger dummy completely dislodged. The seat broke free.
In the second test without side airbags, one attachment point released
and a second one broke, allowing partial separation of the seat from
the floor.
"This didn't worsen the injury measures recorded on the rear dummy,
but a real person in a more complicated real-world crash might not fare
as well. Seats should stay attached because they're part of the restraint
system, and in real crashes vehicles may roll over or be hit again,"
Lund explains. If this hadn't happened, the Uplander with optional side
airbags would earn a rating of acceptable for protection in side impacts.
The seat problem downgrades the rating to marginal. Without the optional
side airbags, the Uplander is poor regardless of the seat problem.
General Motors engineers have identified a fix for the seats and shown
the Institute promising data from a prototype test. When this change
has been made in production models, the Institute will test the Uplander
again and report the results.
Optional side airbags improve performance of Dodge Grand Caravan: The
side test of this minivan was delayed from last year because the manufacturer
was working on changes to improve its performance. Beginning with 2006
models (built after December 2005), side airbags were updated, roof and
side structures were strengthened, and interior door trim was changed.
In the test without optional side curtain airbags, the intruding barrier
struck the driver dummy's head. While this didn't produce high injury
measures, vehicles should be designed to prevent people's heads from
being struck by intruding vehicles, trees, poles, etc.
In contrast, the Grand Caravan with its optional side airbags is rated
good for head protection. The curtain-style airbags deploy from above
the windows to protect people in all three rows of seats.
"In a side impact, the only thing between the driver and an intruding
object is the door and side window. This contrasts with a serious frontal
crash, in which the whole length of a vehicle's front end crushes to
help protect the people riding in the occupant compartment," Lund points
out. "Because there's so little other protection in side crashes, the
airbags are especially important. They can provide enough of a cushion
to prevent the most serious injuries or reduce their severity."
How vehicles are evaluated: The Institute's frontal
crashworthiness evaluations are based on results of 40 mph frontal offset
crash tests. Each vehicle's overall evaluation is based on measurements
of intrusion into the occupant compartment, injury measures recorded
on a Hybrid III dummy in the driver seat, and analysis of slow-motion
film to assess how well the restraint system controlled dummy movement
during the test.
Each vehicle's overall 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. Ratings
reflect injury measures recorded on two instrumented SID-IIs dummies,
assessment of head protection, and the vehicle's structural performance
during the impact. Injury measures recorded on two dummies, one in the
driver seat and the other in the rear seat behind the driver, are used
to determine the likelihood that the driver and/or passenger in a real-world
crash would have sustained serious injury to various body regions. The
movements and contacts of the dummies' heads during the crash also are
evaluated. Structural performance is based on measurements indicating
the amount of B-pillar intrusion into the occupant compartment.
Rear crash protection is rated according to a two-step procedure. Starting
points are measurements of head restraint geometry — the height
of a restraint and its horizontal distance behind the back of the head
of an average-size man. Seats with good or acceptable restraint geometry
are tested dynamically using a dummy that measures forces on the neck.
This test simulates a collision in which a stationary vehicle is struck
in the rear at 20 mph. Seats without good or acceptable geometry are
rated poor overall because they cannot be positioned to protect many
people. |
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