ARLINGTON, VA The Smart
car is getting a lot of attention for its small size and
style, and now it's earning impressive crash test ratings.
In recent Insurance Institute for Highway Safety tests, the
2008 Smart Fortwo, the smallest car for sale in the US
market, earned the top rating of good for front and side
crash protection. Its seat/head restraints earned the second
highest rating of acceptable for protection against whiplash
in rear impacts.
Smart Fortwo is classified a
microcar, meaning it's smaller even than minicars. Weighing
about 1,800 pounds, the Smart is more than 3 feet shorter and
almost 700 pounds lighter than a Mini Cooper. It weighs about a
third as much as one of the heaviest vehicles the Institute has
tested, the BMW X5, a midsize SUV. As the price of fuel climbs
and tougher federal fuel economy requirements kick in, auto
companies are expected to introduce more small vehicles to the
market. The Smart is the smallest car the Institute ever has
"The big question from
consumers is, How safe is it?'", says Institute president
Adrian Lund. "All things being equal in safety, bigger and
heavier is always better. But among the smallest cars, the
engineers of the Smart did their homework and designed a high
level of safety into a very small package."
The Institute's test results
generally demonstrate how well vehicles stack up against others
of similar size and weight. Frontal ratings can't be compared
across weight classes, meaning a small car that earns a good
rating isn't safer than a large car that's rated less than good.
"People base their buying
decisions on a lot of factors," Lund says. "If you drive only in
congested urban areas where speeds are low, a small car may be
more practical than a big one. We conduct crash tests so people
who want small cars can choose the ones that afford the best
The Smart has a crashworthy
design for its size and is equipped with the latest safety gear,
which is especially important in a small car. This vehicle's
standard equipment includes seat-mounted combination side
airbags designed to protect both the heads and chests of the
driver and passenger. Also standard is electronic stability
control (ESC), called electronic stability program in the Smart.
ESC helps drivers maintain control during emergency maneuvers or
on slippery roads. It engages automatically when it senses
vehicle instability, and Institute research has found that ESC
lowers the risk of fatal single-vehicle crashes by about half.
Restraints do more
of the work in frontal crashes:
The Smart mostly lacks a front-end crush zone, which is a key
component in reducing injury risk in serious frontal crashes.
Typically, front-end structures are designed to crush and absorb
crash energy, allowing occupant compartments to
gradually, ideally with little or no intrusion into drivers'
survival space. Then a vehicle's safety belts and airbags slow
occupants further and are designed to spread crash forces more
evenly across people's bodies. The longer the front-end crush
structure of a vehicle, the more gently occupants are slowed and
thus protected from injury.
To compensate for the lack of
front-end crush space, the Smart's restraint system does more of
the work of absorbing energy as occupants "ride down" a crash.
"We recorded a high head acceleration when the driver dummy's
head hit the steering wheel through the frontal airbag," Lund
explains. This indicates the test dummy used up all of the
available ride down room in the Smart's interior.
Smeared greasepaint shows where the
driver dummy's head was protected
from being hit by hard structures by
the side airbag.
A stiff side structure and
standard side airbags contributed to the Smart's good rating in
the side test, which replicates a crash with a pickup truck or
SUV. Injury forces recorded on the driver dummy's head, neck,
torso, pelvis, and left leg all were low. However, the driver
door unlatched during the crash. This confirms a finding of the
National Highway Traffic Safety Administration's side test of a
Smart released last month. The Institute downgraded the Smart's
structural rating from good to acceptable, but the opening
didn't appear to affect dummy movement during the test, and
injury measures on the driver dummy were low. Still, doors
shouldn't unlatch because in some crashes it could allow partial
or complete occupant ejection, especially if an occupant is
Small car safety:
While small cars are safer now than before, so are large cars.
In every category of passenger vehicle (car, SUV, or pickup
truck), the risk of death is higher in crashes of smaller,
lighter models. For vehicles 1-3 years old during 2006, minicars
experienced 106 driver deaths per million registered vehicles
compared with 69 driver deaths in large cars.
People often choose very
light cars for fuel economy, but "you don't have to buy the
smallest, lightest car to get one that's easy on fuel
consumption," Lund points out. "The Toyota Prius, for example,
earns good front and side crash test ratings. It gets better
fuel economy than a microcar, but it's bigger and weighs more so
we would expect it would be more protective in serious crashes."
How the Smart was
evaluated: The Institute's
frontal crashworthiness evaluation is based on results of a 40
mph frontal offset crash test. A 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
The side evaluation is based
on performance in a crash test in which the side of a 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 an instrumented SID-IIs dummy in the driver seat,
assessment of head protection countermeasures, and the vehicle's
structural performance during the impact.
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 can't be positioned to protect many people.
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