Passenger Cars and Safety 2009

As a class, cars have a few advantages over light trucks and a few disadvantages. As is the case in any body style, it's easier to judge the crashworthiness of better-selling models, like sedans, because low-volume cars — such as most wagons and convertibles — often go untested.

Passenger Car Pros and Cons

In the wake of skyrocketing fuel prices, more SUV, pickup truck and minivan owners than ever are considering downsizing to the efficiency of a car. This raises anew the question of passenger-car safety on roads that are shared with larger vehicles. Car safety has improved markedly versus light trucks since the turn of the century. While the consequences of size and weight differences have by no means been overcome, cars do have some advantages.

As a class, cars and wagons' main advantages over light trucks are their lower center of gravity, their size and their braking. Their lower center of gravity translates to a lower likelihood of rollover. While a car that goes off the pavement can roll, its lower center of gravity makes it less likely to do so than pickup trucks or SUVs, which are more easily "tripped" by a curb or soft shoulder. Cars' lower center of gravity also makes them more nimble and capable of avoiding a collision, as do their smaller size and typically shorter braking distances.

Unfortunately, a couple of passenger car advantages are also disadvantages: The lesser weight and lower height make them vulnerable to heavier, higher vehicles. Historically, pickups and truck-based SUVs have not been as meticulously designed to absorb crash energy, but their weight and height make up for it in crashes with lighter vehicles, whose occupants pay the price.

Aside from the weight issue, it's a matter of compatibility: A high truck can ride up over the most robust part of a car's frame structure, bypassing its crumple zone and plowing into its cabin.

There's evidence that SUVs are becoming less deadly to occupants of cars with which they collide. Many manufacturers have worked since 2003 to make SUVs more compatible in crashes with smaller vehicles by lowering their frames to engage a car's crumple zones. The Insurance Institute for Highway Safety cross-referenced a list of such SUVs with fatality data through 2005 (the latest year for which data have been tabulated) and found that the fatality risk for a belted car driver was 18-21 percent lower when crashing head-on with a compatible SUV than with a conventional one. (There's practically no change for unbelted drivers.) The side-impact results are more dramatic: a 47-49 percent decrease in car occupant fatality risk when hit by a compliant SUV.

According to the National Highway Traffic Safety Administration, in 2007 alone the number of fatalities among car occupants in collisions with light trucks (SUVs, pickups and minivans) decreased by 9 percent, the fourth consecutive year of improvement. Nonfatal injuries decreased by 5.3 percent. Truck deaths in the same scenario are down 6.9 percent. (Because compatible vehicles better exploit each other's energy-absorbing structures, both sides benefit.) More detailed 2007 crash records also seem to support the claim that changes in light truck bumpers have improved passenger-car survivability: NHTSA says fatalities are down 12 percent among car occupants and 24 percent among light-truck occupants when the truck strikes the side of the car. The statistics have also improved for when a car T-bones a light truck: Deaths are down 27 percent in the striking passenger car and 24 percent in the struck vehicle. SUV and pickup manufacturer efforts have centered on the bumpers, not the sides, so improvement here may be attributed to improvements in car construction.

The Honda Fit has been designed to better absorb an impact from a larger vehicle, such as a truck.

A leader in this area, Honda has been addressing the compatibility issue with Advanced Compatibility Engineering, which designs a car's structure to engage a higher vehicle — not leaving this responsibility to the opposing truck's design.

Though it's become less extreme year after year, there's no denying the disparity between cars and light trucks. Even with the improvements cited above for 2007, NHTSA reports that in head-on collisions between cars and trucks, 3.6 times as many passenger-car occupants died. When trucks struck cars in the side, 18 times as many car occupants were killed as truck occupants. Buyers who are concerned about compatibility and see no well-rated cars they desire should consider a higher-riding car or crossover vehicle, which increases the chance of compatibility in a crash.

A side impact from a truck or SUV is perhaps the greatest danger. There are just inches and practically no steel between a truck bumper and a car occupant's upper body. This is why side-impact airbags are a must, as discussed below. Features can't compensate for weight and height differences, but they can certainly help.

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Features to Look For

ABS and disc brakes: Antilock braking systems, increasingly a standard feature, are well worth having. They shorten stopping distances in some situations, but their main benefit is that they allow the driver to steer even when applying maximum braking. Though drum brakes are more susceptible to lockup, ABS mitigates the problem. Still, four-wheel disc brakes are optimal.
Airbags aplenty: A full set of airbags can improve an occupant's survivability dramatically. Frontal airbags are required on all cars; the side-impact variety are not. Side airbags that deploy from the seatbacks generally are intended to protect the occupant's torso, though some extend higher for head protection — especially in the absence of side curtain airbags.

The curtains deploy downward from the ceiling, covering all the side windows. (The Porsche Boxster and Volvo C70 are two convertibles in which curtains deploy upward from the doors.) This type has proved critical in protecting car occupants, especially when T-boned by a higher vehicle. This type of crash poses a high risk of head injury, which is the least survivable type of trauma. (It's also the reason we have rejected the National Highway Traffic Safety Administration's side-impact star ratings, as they do not factor in head injury.) According to NHTSA, when a car strikes the side of a light truck, 1.6 times as many truck occupants were killed in 2007 than were occupants in the opposing car. This illustrates that even light-truck occupants — whose chances of survival are greater when they strike a car — are disproportionately at risk when struck from the side by a car.

There's little or no concern about side curtain airbags harming children. But conventional side-impact airbags can be dangerous for an out-of-position child, so they seldom appear in backseats. The Hyundai Genesis and some German luxury sedans are notable exceptions. When there are rear bags, car dealers might be able to deactivate them. If you're concerned about a side-impact airbag in the front passenger seat, consider buying one of the Honda or Acura models that automatically disables the side bag when the seat occupant is leaning too close to the door.

The latest vehicles also feature advanced frontal airbags, which deploy at more than one level or depth for occupants of different sizes. They employ the Occupant Classification System in the front passenger seat and crash-severity sensors to determine the correct airbag intensity. All cars and light trucks produced after Sept. 1, 2006, are required to include advanced frontal airbags.

Note that, even with OCS, airbags are not effective unless used with seat belts. It is a common misconception that seat belt use is unnecessary in the backseat. This is utterly false. Aside from greater risk to the backseat occupants themselves, the Journal of the American Medical Association has reported that an unbelted rear-seat passenger increases the front-seat occupant's risk of death by 20 percent. Why? Because in a frontal collision at just 30 mph, an unbelted 120-pound backseat occupant will strike whatever's in front of him with the force of more than 1,000 pounds.

We can't emphasize enough the value of airbags. For just a few hundred dollars, they can be the difference between serious injury and walking away from a crash. If they seem expensive, how much is your health insurance deductible?
Electronic stability system: Known by innumerable names, most of which include the word "stability," these computer-based systems brake individual wheels and — when necessary — control the throttle to keep the vehicle on the intended path in low-traction situations. Increasingly, this feature is standard on luxury vehicles, and Honda has committed to including it in every all-new and re-engineered vehicle within the next few years. Since the 2007 model year, IIHS has bestowed its highest honor — Top Safety Pick — only to models that offer stability systems. Because they help prevent conditions that may lead to rollovers, 95 percent of SUVs now include stability control as standard equipment. For 2009, 64 percent of cars have standard stability systems, and 19 percent offer them as an option. The prevalence will only increase in the future; NHTSA has mandated that all models have stability systems by the 2012 model year.
Head restraints: Not simply "headrests" for occupant comfort, head restraints are intended to protect against whiplash injuries, particularly in a rear-end collision. Some of the vehicles tested by IIHS so far provide inadequate to fair protection, mainly because the head restraints don't extend high enough or aren't close enough to the occupant's head to prevent injury.

Buyers should look for head restraints — for every seating position — that extend high enough for the tallest likely occupant, and rest, or can be positioned, close to the head. Better still, active head restraints move forward in a collision to catch the occupant's head and ease it back. Once rare in affordable cars, the feature is proliferating among many brands, especially Honda, Hyundai, Kia, Nissan, Subaru and Volkswagen.
Tilt/telescoping steering wheel: Modestly priced vehicles have manually adjusted steering wheels that infrequently include a telescoping adjustment. This is unfortunate. Aside from making the driver as comfortable as possible, the telescoping adjustment in particular helps distance the driver properly from the airbag, regardless of his or her size. The next feature serves a similar purpose.
Adjustable pedals: Adjustable pedals serve a similar purpose as the telescoping steering wheel, allowing drivers to distance themselves optimally from the steering wheel without compromising pedal reach. Having both features is a best-case scenario.

Xenon and adaptive headlights: Though they're mainly found in luxury vehicles, some more affordable cars offer xenon high-intensity-discharge headlights as an option. They are superior to conventional incandescent headlights because they are brighter, they cover a wider field of view, and they produce more ultraviolet light, which better illuminates reflective road signs. Even cars that lack this headlight type can vary in the amount of light they emit and how they distribute it.

If you frequently drive in areas where wildlife strays onto the road, you might want to check a prospective vehicle's performance in this area before buying. Another option is adaptive headlights, which swivel in the direction of a turn. In a sharp corner, they can illuminate the inner curve that otherwise would remain in darkness. It's not a gimmick; in certain circumstances, it's well worth having. The vast majority of adaptive headlights are also xenon types, but conventional projector-beam headlights that swivel have begun to appear.
Collision mitigation systems: Exclusive to luxury cars, there are now features that sense an impending collision and attempt to prevent it, or at least prepare the car and its safety features for impact.

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What About Wagons and Hatchbacks?

Hatchbacks, like the 2009 Saturn Astra, aren't always crash-tested by the various agencies.

In cases where there are wagon or hatchback versions of a sedan model, frontal crash tests tend to yield similar results. This is helpful because wagons are usually low-volume vehicles, which the testing agencies don't analyze. Possible differences in side-impact performance are less clear.

One of the greater and little-known hazards of hatchbacks and wagons involves cargo. Where a sedan carries cargo in a self-contained trunk, wagons and — to some extent — hatchbacks house people and cargo in the same cabin. In a collision, especially a frontal one, unrestrained cargo flies forward with a force exponentially greater than its weight. At 55 mph, a 20-pound parcel exceeds 1,000 pounds of force.

Whether the cargo stays in the back or not depends on many factors, such as the cargo's height relative to the seatbacks, how much the vehicle's rear end rises upon impact and innumerable other dynamics.

The only safe way to travel with cargo in a hatchback or wagon (or an SUV for that matter) is to restrain it. Tying it down is the most obvious cure, but some wagons offer retractable nets or cages at the backseat's backrests that can help contain objects in the cargo area. Is this step a drag? Yes. The most careful drivers will do it anyway. If you choose not to, understand that you're playing the odds.

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Children and Cars

Overall, cars have pros and cons as child-carriers. Their lower height facilitates child-seat installation compared to many SUVs. At the same time, backseat space seems more limited than ever. Children might be small, but child-safety seats are huge, and it's now recommended that children stay in booster seats until much later in life. Few cars will accommodate two child seats and an adult in the backseat.

Compared to minivans and some SUVs, cars can hinder child-seat installation. Low ceilings and contoured backseats, especially in coupes, can prevent a secure fit. Securing the seat with seat belts, the conventional method, calls for the adult to put a knee into the seat while tightening the belt — hard to do in the back of a 2+2. People in this situation should consider a child seat with Latch straps for simpler installation. All new cars have at least two Latch anchors in their backseat. Look for a car that has a pair dead center in the backseat, the safest place for an occupant. (Only two pairs are required, and too often they appear in the outboard seats.) This keeps the child as far away as possible from the car's perimeter on all sides.

The rules for transporting children in cars are the same as they are for other vehicle types: The proper child-safety or booster seat should be used for their age and size, and they should be secured in the backseat. The front passenger seat should be avoided at all costs, especially with a rearward-facing child-safety seat. If you must place a child seat in the front, in a two-seat car, you must have either OCS or a defeat switch to turn off the airbag.

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Convertibles: A Safety Mystery

The Porsche Boxster was the first convertible to offer a side-impact airbag.

Convertibles, a category that includes many sporty roadsters (two-seat convertibles), are even more of a mystery. Their production volume is lower still, and most go untested. The design of convertibles alone raises serious questions about their safety:

Crash tests: Hardtop crash tests are no indication of how a convertible version of the same model withstands a crash. A rigid roof plays a pivotal role in managing crash energy. Lacking this structure, a convertible may have completely different test results.
David versus Goliath: If full-size pickups and SUVs are the Goliaths of the modern age, then little roadsters like the Audi TT and Mazda MX-5 Miata are the Davids. Despite the biblical tale's surprise climax, in this case my money's on Goliath. As mentioned above, a vehicle's weight is by no means the only factor in the collision equation, but it's a major one. The mismatch in height is also a concern.
Side impacts are worrisome: Convertible occupants may be in greater danger in a side-impact collision. Automakers do what they can to reinforce the doors, but the lack of pillars and a roof means there may be little or no structure to obstruct an intruding bumper. This is particularly true of small, low-slung roadsters, the doors of which might be even with, or lower than, a truck's bumper.

Many convertibles now offer side-impact airbags, most of which protect the torsos of front-seat occupants and some of which extend higher to provide head protection. Currently only two models we know offer side curtain airbags, which have proved very effective in hardtop vehicles at protecting all occupants in a side-impact collision. Porsche was the first, with the 2005 Boxster's head-protection airbags that deploy upward from the side window rails. The 2007 Volvo C70, a retractable-hardtop convertible, now has a similar system.
Seat belts are a must: Seat belts are always a must, but in an open-air vehicle there's an even greater possibility of ejection, which multiplies the chance of fatality.
Roll protection: Convertibles require some type of protection to maintain occupant headroom in the event of a rollover. Automakers typically reinforce the windshield frame and include a roll bar. The most common roll bar is actually a pair of inverted U-shaped steel tubes positioned behind the cabin (see the Audi TT roadster). Some manufacturers, including Audi, BMW and Jaguar, now equip convertibles with active roll bars. They remain out of sight behind the backseat — providing maximum visibility — unless the car begins to tip, at which point they deploy upward and serve as fixed roll bars would.

Here again, automakers certify their convertibles for protection in a rollover, but NHTSA performs no tests.

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Posted on 10/22/08