What You Need to Know About Sports Cars and Safety
When it comes to safety, sports cars (and, to some extent, sporty cars) have some distinct advantages. But in other aspects — including those on which we rely most in determining a vehicle's safety — the picture is unclear.
- Active Versus Passive Safety
- Crash Tests: If Only We Had More
- Features That Improve Safety — and Hamper It
- Sporty Cars and Extreme Weather
- Sports Cars and Child Safety
- Convertibles: A Safety Mystery
Where sporty cars tend to excel is in active safety, but their passive safety is more of a mystery than it is in most vehicle classes.
Active safety involves features and attributes that help vehicles avoid collisions. Here, a sporty car's effective braking and nimble handling give it an edge over, say, a pickup truck or SUV that must be driven more carefully and typically doesn't stop as short.
Similarly, a sporty car's low center of gravity and road-hugging suspension and tires allow it to make evasive maneuvers — or take sharp or hairpin turns — at speeds that would cause a truck to roll over and an average car to slide off the road. Features like antilock brakes and electronic stability systems are readily available in sports cars as well. So in terms of single-vehicle wrecks, the sporty car is inherently less prone. Now, that's the car I'm talking about. The driver is a different story.
The driver is one reason it's difficult to gauge how well sports cars protect their occupants in a collision. People who buy sports cars tend to drive them aggressively — speed, take risks and push the car closer to its limits. Though a sports car's limits are well past an average car's, its driver is more likely to test those limits than the average driver does those of the average car. We generally rate a vehicle's safety using a combination of real-world data and crash tests. The problem with real-world histories — such as fatality data — is they reflect not only the vehicle but also the way it's driven. (The same is true of reliability data, which reflect how a vehicle is driven and maintained as well as its inherent robustness.)
Passive safety features are the ones that protect you when active safety features have failed in preventing the collision. Seat belts, airbags, head restraints and seats that change their geometry to position the body optimally for impact are all examples of the growing category of passive safety provisions.
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In situations where it's possible that real-world data has been skewed by driver behavior, we rely even more on crash tests, which tell us how well the vehicle protects occupants in a crash. Unfortunately, here sports cars run into yet another brick wall, as it were.
Neither of the testing agencies — the Insurance Institute for Highway Safety nor the National Highway Traffic Safety Administration — crash test every vehicle on the market, and the models they forgo are those with the lowest production volume. Sports cars, as a class, are the vehicles with the lowest volume. IIHS — by far our preferred provider — began to test convertibles in 2007, with a focus on the top-sellers. Still, there isn't sufficient data to create a Top 10 list for the top-performing sports cars in crash tests.
Of the two agencies, NHTSA has crash-tested more sports cars than has IIHS. Its frontal star ratings give you an idea of how a car would fare in a head-on collision with a brick wall. As we explain in the Guide to Interpreting Crash Tests and Rollover Ratings, we deem NHTSA's side-impact ratings misleading and not worthy of consideration.
All vehicles sold in the United States must be certified by their manufacturers as capable of withstanding 30-mph frontal and 33.5-mph side impacts. If you don't see test results on a car that's currently on sale, that means the government hasn't tested it.
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We always emphasize that safety features don't automatically mean a vehicle protects its occupants well in a crash, but they seldom hurt. Following are some features and attributes that make sporty cars safer — and some that can make them less safe, followed by special considerations for extreme climates, families and convertibles.
Positives for safety:
- ABS: Antilock braking systems allow vehicles to stop shorter in almost all circumstances and to remain steerable even during a panic stop. We highly recommend this feature.
- Traction control: Traction control simply prevents traction loss during acceleration by limiting the throttle and applying braking to a wheel that's spinning (ABS is required for all traction control). Unfortunately, many systems are so conservatively calibrated that they make it difficult to build any momentum on loose snow or sand. An intermediate traction control setting that allows some wheelspin is a bonus in this case. It has appeared on some SUVs, as well as BMW cars, and manufacturers as a whole are trying to make their traction control less sensitive so cars don't bog down. We recommend traction control, particularly on rear-wheel-drive cars. See Sporty Cars and Extreme Weather.
- Electronic stability systems: Electronic stability systems (under names such as ESP, VDC, DSC, StabiliTrak and others) automatically include ABS and traction control and add the capacity to sense when the car is going out of control and to intervene by applying selective braking to individual wheels. It's not just for slick roads. Sports car drivers, who are most likely to test a vehicle's limits — and the laws of physics — are prime candidates for this feature. We highly recommend it. Though it's one of the costlier options, if it saves you one insurance deductible it's paid for itself. For 2009, 64 percent of cars have stability standard, and 19 percent offer it as an option. The prevalence will only increase because NHTSA will require the feature in all models beginning with the 2012 model year.
- Airbags galore: There are now front, side, side curtain and knee airbags. All types are worth having.
- Adjustable head restraints: What's taken for granted in regular cars is often missing in sports cars. Because they're more likely to have one-piece, high-back bucket seats, sports cars sometimes forfeit the adjustable head restraint. (Head restraints are intended to prevent whiplash-type injuries; they aren't "headrests" for occupant comfort.) Aside from the issue of height, the best head restraints adjust forward and backward to minimize the distance to the occupant's head. One-piece seats are always a compromise in this regard.
- Tire pressure monitoring systems: If proper tire pressure is important on all other cars, it's more so on sporty cars. Over- or underinflated tires change the vehicle's dynamics radically. I'm concerned that a TPMS will prove useful only in the most extreme circumstances — such as a blowout or dangerously low pressure — and will otherwise induce drivers to ignore their tire pressure even more than before. But I still recommend it if it's used properly. For roughly a decade, a TPMS was included on any car with run-flat tires as well as some without. Since Sept. 1, 2007, this feature has been required on all new cars.
- Parking assist and rearview cameras: Systems that detect or display objects behind and, in some cars, in front of the vehicle using a camera or beep tones mostly help protect your bumper paint. But they can also help prevent backing into a child, animal or toy. There's no substitute for extreme caution on the driver's part, but this is a good supplement.
- Limited visibility: Though it's not a universal trait among sports cars, many have limited rear visibility in the form of large blind spots.
- Low relative height: Sports cars tend to sit closer to the ground and be shorter overall than the average vehicle. This difference in height represents a mismatch in collisions with other vehicles, especially pickup trucks and SUVs. Trucks' propensity to override a shorter vehicle's crumple zones is a serious concern for low-slung sports cars.
- Light weight: Automakers attempt to limit a sporty car's weight to increase acceleration. A vehicle's weight is by no means the only factor in the collision equation, but it's a major one. Lighter vehicles fare worse in crashes with heavier ones, all other aspects being equal.
- One-season tires: Summer performance tires are as dangerous in winter weather as they are safe when it's warm. See Sporty Cars and Extreme Weather.
- Modifications: Customizing is more popular now than it's been in decades, and possibly more than ever. Sporty cars are the vehicles most often modified by their owners. It's important to recognize that vehicle engineering is a delicate balance, and compromise is unavoidable. Changing one aspect of a car's performance invariably changes something else. What seems to be an improvement in, say, handling may actually diminish roadholding in some circumstances — such as different road surfaces or inclement weather. With all due respect, the safest thing more than 99 percent of owners can do is recognize that — in the grand scheme of things — they have no idea what they're doing, and that it's best not to change any aspect of the car too radically.
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The caveats here are mostly about sporty cars in winter weather, but the change of seasons is relevant because what's good for one season tends to be bad for another. Technology has made sporty cars more drivable in winter climates than they've ever been, but important issues remain.
- Tires are tremendously important: Summer performance tires are the best choice for grip in warm weather, but they simply should not be used in the cold of winter, and especially not on snow or ice. Everything that makes them effective when warm — soft rubber compounds and wide tread with minimal grooves — makes them hazardous on snow and ice. All-season tires (those with the M+S designation on the sidewall) are a great compromise, but if you insist on dedicated summer tires, you'll need another set (perhaps on cheap steel wheels) if you want to drive on snow and ice.
Narrow tires are more effective on snow, but sporty cars tend to have the widest tires of any vehicle type, relative to their size and weight. Winter tires, the modern designation for snow tires, can make a world of difference in a sporty car, though they may increase stopping distances in warm, dry circumstances compared to an all-season design. Winter tires have the M+S designation plus a symbol of a snowflake over a mountain. For a couple of sports cars, like the Dodge Viper, only summer tires are manufactured. We think these cars should stay off the road in winter. Don't think all-wheel drive is a substitute for proper tires. See below.
- Rear-, front- and all-wheel drive: Many driving enthusiasts prefer rear-wheel drive for the balanced weight distribution and the ability to control the car's attitude with the accelerator. Traction control has improved winter performance, but rear-wheel drive remains the last choice in snowy weather, especially in regions with hills or mountains. Front-wheel drive is a better choice and all-wheel drive is better still, especially in those hilly areas. Note: Having all-wheel drive doesn't invalidate the tire warning above. In my experience, winter tires can make viable an otherwise undrivable rear-wheel-drive vehicle.
- Engine power: Powerful engines can make a car less safe on slick roads. The more power (or, technically, torque), the easier it is to induce a power skid that causes a loss of control. This is why the traction control and stability systems detailed above are useful, though, historically, traction control has made it difficult to accelerate in loose snow where some wheelspin helps the tires "paddle" along. Systems that allow you to select an intermediate mode or to turn off the traction control but not the stability — such as StabiliTrak on some Cadillacs and Chevrolets — are a bonus. Surprisingly, the less conservative traction control action in some sporty cars, such as Porsches, allow a little wheelspin when accelerating, which can be effective on snow.
- Transmission choice: Manual transmissions are favored by sport purists, but there are pros and cons when operating them in snow. The hard connection of a mechanical clutch makes it difficult for some drivers to accelerate from a stop on snow without spinning the wheels. In this regard, most automatic transmissions have an advantage because there's more "give" in their fluidic torque converters. On the flip side, upshifting quickly through the gears and limiting engine rpm minimizes torque at the drive wheels, which helps prevent wheelspin. This requires a manual transmission or an automatic with clutchless-manual shifting — or a winter mode that achieves the same effect.
- Ground clearance: Decreasing a car's ground clearance through suspension-lowering kits or smaller tires may lower its center of gravity and/or improve aerodynamics, but it also diminishes the car's ability to travel over snowdrifts. I once bogged down in a low-riding Audi TT, even though it had all-wheel drive.
- Modifications: Again, virtually every modification an owner can make to increase performance will make it less conducive for use in winter climates. Lowered suspensions, increased power, summer tires and lower-profile tires increase the likelihood of getting stuck, compromising traction or sustaining damage because of the reasons detailed above.
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Sports cars are probably the worst choice for transporting children, though sporty versions of luxury coupes and sedans tend to be more flexible. Here are two issues to consider:
- Where to put the baby: The safest place for a child, including a baby in a child-safety seat, is in the center of the backseat, as far as possible from the car's perimeter in all directions — and away from airbags (see below). The obvious problem is that many sports cars have only two seats. The less obvious issue is that the backseats in models that do have them often are small and/or lack a center position. Parents have learned that child-safety seats are large and oddly shaped. Contoured seats make it difficult or impossible to secure a seat tightly — and don't forget that the adult requires plenty of room to install the seat properly, perhaps kneeling in it to tighten the seat belt. Two-door models hinder this. In this instance, a seat with Latch child-seat anchors is helpful. Again, sedans are a better option for those who want to transport kids.
- Airbag hazards: Airbags have proved beneficial for everyone except small adults and children. You simply don't want a child anywhere near an airbag (with the exception of side curtain airbags that deploy downward along the side windows). This causes a problem in two-seat cars. If it's absolutely necessary to transport a baby in a two-seater, the only way to do so is by deactivating the front airbag. Automakers that allow this do it in one of two ways: a key switch that must be turned manually, or an automatic occupant classification sensing system, which is an integral part of the advanced frontal airbags that have been required on all new vehicles since the 2006 model year. The latter is much preferred because it doesn't require the driver to remember to disable the airbag for a child and reactivate it for an adult.
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Convertibles, a category that includes the many sporty roadsters (two-seat convertibles), are even more of a mystery. Their production volume is lower still, and historically most of them have gone untested. IIHS began to crash midsize convertibles in 2007, including many top-sellers, but at the beginning of the 2009 model year, the category includes the same 10 models that had been rated a year ago, and we're hoping to see more soon. The tests are especially important for convertibles, whose design alone raises serious questions about their safety:
- Non-convertible 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 roadster 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 only three models 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 feature has since been incorporated in the 911 Cabriolet, and the retractable-hardtop Volvo C70 has had a similar system since its 2006 redesign.
- 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. 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 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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