Active Safety Features
When buying an SUV, it's important to consider its safety features. These fall into two categories: active and passive. Active safety features help the driver avoid an accident, while passive safety features help protect occupants in the event of an accident.
The following active safety features are designed to help you avoid an accident.
Most vehicles today are available with anti-lock brake systems (ABS). If anti-lock brakes do not come standard on the SUV you intend to buy, be sure to choose ABS as an option. While ABS does not generally help a vehicle stop quicker than conventional brakes do on dry pavement, it has two distinct advantages. First, and most importantly, ABS allows you to steer your vehicle under full braking power. This is because ABS pumps the brakes many times per second (much faster than a human can), preventing wheel lockup and helping to maintain steering control. That means when that car suddenly stops in front of you, you can brake hard and still steer over to the shoulder if you won't stop fast enough to avoid an accident. In these instances, ABS can be the difference between a fender-bender and a close call.
At a Porsche-sponsored driving school, instructors demonstrated how different safety systems work to prevent vehicle skids.
Second, ABS can help you stop quicker on slippery pavement. Porsche invited Consumer Guide® to Barber Motorsports Park in Birmingham, Alabama, for an SUV safety driving program. In simulated icy conditions at the Porsche program, an ABS-equipped vehicle stopped in a reasonable distance. With the ABS deactivated, our test Porsche Cayenne continued to skid for a distance that would have been at least twice as far as the ABS-equipped vehicle. In fact, it wasn't until the Cayenne left the simulated icy surface and got onto a wet asphalt surface that it had any grip at all. A well-trained driver may be able to pump the brakes and prevent a skid, thus stopping quicker. However, most drivers press the brake pedal in an emergency situation, making ABS the better choice.
Anti-skid systems, often referred to as electronic stability control (ESC), go by other names depending on the manufacturer. GM calls it StabiliTrac, Ford dubs it AdvanceTrac, and Chrysler calls it Electronic Stability Program (ESP). Other names include Vehicle Dynamics Control (Subaru), Dynamic Stability Control (Volvo), Vehicle Stability Assist (Honda) and Vehicle Stability Control (Toyota). For a complete list of anti-skid system names, check out the NHTSA's ESC-equipped vehicles list.
An anti-skid system uses several sensors to detect a loss of grip in your vehicle, then works with the anti-lock brake system to apply individual brakes to help keep the vehicle on its intended path. In some cases, an anti-skid system also reduces engine power.
So what does this mean to the driver? Well, if you approach a corner too rapidly and your vehicle begins to plow straight ahead, an anti-skid system will detect that the vehicle is not on its intended path and intervene by applying the inside brakes. This will rotate the vehicle through the turn and, hopefully, save you from going off the road. Anti-skid systems can't defy the laws of physics, so they won't help you take a 90-degree turn at 100 mph, but they can be quite helpful in most driving. Anti-skid systems are available on most SUVs, but they are usually optional. Make sure to order your SUV with an anti-skid system.
Roll Stability Control
Roll stability control works very much like an anti-skid system, but uses additional sensors to detect an impeding rollover. It then activates the anti-skid system. Roll stability control systems work on flat pavement; they can't prevent rollovers caused by hitting a curb or sliding into a ditch. Also, roll stability control should not be confused with what may be called rollover protection; these systems deploy curtain-side airbags when detecting an impending tip. Volvo, Ford, Mercury, Lincoln, Land Rover and Jeep have roll stability control systems, and Dodge plans to release one soon.
All-wheel-drive and four-wheel-drive systems allow all four wheels to transfer power to the road. Though not generally considered a safety feature, AWD or 4WD can provide the additional traction you may need to accelerate out of harm's way.
Four-wheel Independent Suspension
Four-wheel independent suspension allows each wheel to react individually to bumps in the road. All SUVs have independent front suspension, but not all have independent rear suspension (IRS). Those without IRS have solid rear axles that cause both wheels to react to a bump in the road when either tire hits that bump. While four-wheel independent suspension is also not generally considered a safety feature, keeping at least one tire planted on the road could possibly make the difference in avoiding an accident, especially when taking bumpy corners at high rates of speed.
Next, we'll take a look at passive safety features.