Passenger Cars and Safety

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
Features to Look For
What About Wagons and Hatchbacks?
Children and Cars
Convertibles: A Safety Mystery

Passenger Car Pros and Cons

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, size and 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.

A side impact from a truck or SUV is perhaps the greatest danger to passenger cars. 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. Back to top

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 is 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 through 2010, as they did not factor in head injury. Newly revamped testing for 2011 remedies this problem, but the number of cars tested is small and will grow slowly.

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 sedan 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.

Note that airbags are not effective unless used with seat belts. It is a common misconception that seat belt use is unnecessary in the backseat. 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.

Electronic stability system: Known by innumerable names, most of which include the word "stability," these computer-based systems brake individual wheels and control the throttle to keep the vehicle on the intended path in low-traction situations. NHTSA has mandated that all new vehicles have stability systems by the 2012 model year, so the feature has proliferated and is standard on almost all luxury vehicles and SUVs.
Head restraints: Not simply "headrests" for occupant comfort, head restraints are intended to protect against whiplash injuries, particularly in a rear-end collision. The Insurance Institute for Highway Safety rates cars for rear impact with the same Poor/Marginal/Acceptable/Good ratings used in the organization's frontal-offset and side-impact crash tests.

Buyers should look for head restraints for every seating position that extend high enough for the tallest likely occupant and 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.

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, cover a wider field of view and 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. The latest feature is headlights that automatically switch between low and high beams by sensing other cars' headlights and taillights. BMW and Mercedes supplement their headlights with optional night vision displays.
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. Back to top

What About Wagons and Hatchbacks?

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. Back to top

Children and Cars

Overall, cars have pros and cons as child carriers. Their lower height facilitates child-safety seat installation compared with many SUVs. At the same time, backseat space seems more limited than ever, 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 with minivans and some SUVs, cars can hinder child-seat installation. Low ceilings and contoured backseats, especially in coupes, can prevent a secure fit. 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 --preferably the center seat, as it is as far as possible from the car's perimeter on all sides. The front passenger seat should be avoided at all costs, especially with a rear-facing child-safety seat. If you must place a child seat in the front of a two-seat car, you must have either a defeat switch to turn off the airbag, or the Occupant Classification System, which does the same automatically. OCS has been required in new cars since September 2006. Back to top

Convertibles: A Safety Mystery

Convertibles are even more of a mystery. They sell even less than regular sports cars, and historically most of them have not had crash tests. The tests are especially important for convertibles, whose design alone raises questions about their safety:
•  Non-convertible crash tests: Tests of a non-convertible car are no indication of how a convertible version of the same model will withstand a crash. A rigid roof plays a pivotal role in managing crash energy. Lacking this structure, a convertible will likely 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 that protect the torsos of front-seat occupants. Some have so-called combo bags that are taller and designed to provide head protection as well, but currently few offer side curtain airbags, which have proved very effective in hardtop vehicles at protecting occupants in a side-impact collision. New convertibles that do employ curtains, which deploy upward from the side window rails, include the Porsche Boxster and 911 Cabriolet and the retractable-hardtop Volvo C70.
•  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 sufficient 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. Designers have succeeded in making these a design element in many ragtops. Another approach is the "basket handle," a structural member that spans from one side of the cabin to the other, forming B-pillar equivalents. This member also stiffens the vehicle structure and supports the middle of the raised roof. Some manufacturers, including Audi and BMW, now equip convertibles with active roll bars. They remain out of sight behind the backseat improving the driver's rear view 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 has not tested them for rollovers. Back to top

© Cars.com 10/25/2010