Toyota Prius first hybrid to be crash tested by IIHS

This April marked the first crash testing inspection of a hybrid vehicle by the Insurance Institute for Highway Safety. The Toyota Prius, which combines a gas engine and an emissions-free electric motor, is Toyota's hybrid baby (although it's about five years old), and boasts 650 miles between fill-ups, according to Toyota's site.

Although it didn't earn the Institute's coveted "Top Safety Pick" stamp of approval, it certainly didn't do poorly. Read on to hear what the IIHS had to say of Prius:

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[...] 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.

(Source: IIHS)