Safer (and Sportier) Utility Vehicles


  • Stability Control System Off

    Stability Control System Off

    With the stability control system off, we can see how this driver is frantically countersteering to catch the Highlander's sliding tail. | March 18, 2010

7 Photos

There's More to Safety than Airbags
Ask any number of people about state-of-the-art safety features and they'll typically blather on about those of the passive type, which offer protection in an accident. These folks will probably mention airbags of all kinds — side-impact, side curtain, even knee bags if they're that much in the know. Less famous are crumple zones, side-impact door beams and automatically locking retractors on the seatbelts.

But how about avoiding an accident in the first place? That's where the science of active safety comes into play. A vast array of technological advances in the past decade has done wonders to increase active safety. We recently attended a pair of SUV safety events put on by Toyota and Porsche.

Active Safety's Alphabet Soup
Before we get into the nitty-gritty of why these technologies make SUVs safer, a brief review on what all those abbreviations stand for is in order.

Antilock brakes (ABS) have been around for over 20 years and work by rapidly pulsing the brakes when lockup is detected, such as when braking hard in the rain. This action allows the driver to retain steering control, so the chances of avoiding an accident are increased greatly.

Another couple of advances in braking are Electronic Brakeforce Distribution (EBD), which automatically applies more braking power to the wheels with the best grip, and BrakeAssist (BA), which automatically applies full braking power when a panic stop is sensed via rapid pedal movement, such as when the driver stabs the brakes.

Traction control prevents wheels from spinning in slippery conditions by automatically cutting engine power, lightly applying the brakes or both.

A more recent techno triumph aimed at keeping vehicles on the intended path and away from magnetic telephone poles, hungry ditches and other motorists is stability control. By considering things such as steering wheel angle and yaw rate (the rotation of a body about a vertical axis, such as when a car starts to "fishtail"), then modulating the throttle and/or selectively braking one or more wheels, stability control systems keep the car going where the driver wants. Manufacturers have different names for their stability control systems, such as ESP, VDC, StabiliTrak, and so on.

Stability Control, Version 2.0
At the Toyota event, held at Toyota's 12,000-acre Arizona Proving Grounds, the engineers unveiled Toyota's latest version of active safety technology. Called VDIM (for Vehicle Dynamics Integrated Management), Toyota's new system optimizes vehicle control by adding new features — electronically controlled brakes (ECB) and electronic power steering (EPS) and having them work in concert with the stability control (VSC), ABS, EBD and BA systems. Faster processing speed also promises more transparent operation of the system.

Got all that?

By having so many watchdogs looking out for trouble (potential skid situations and the like), VDIM is able to use one or all of these individual components to correct things before the driver even senses any trouble.

We drove a Highlander equipped with Toyota's standard stability control system. When running through a loose dirt course, it kept us pointed in the right direction. At the same time, it felt intrusive and somewhat herky-jerky as it did its magic to keep us in line.

But then we drove a Highlander Hybrid, which has the new VDIM system, through the same slalom. The new system made the old one feel crude by comparison. The VDIM was virtually invisible in operation, making it seem as if the Highlander Hybrid was guided by the hand of God.

By gathering more data more rapidly and having the ability to act quicker and more progressively, VDIM is able to intervene before things start to get out of shape. This superb system is standard on the Lexus GS 430 and RX 400h, as well as the Toyota Highlander Hybrid.

Formidable Technology for Four-Wheeling
Toyota also demonstrated its Kinetic Dynamic Suspension System (KDSS), which comes on the Lexus GX 470. By allowing the decoupling of the GX 470's front and rear stabilizer bars, KDSS allows greater suspension articulation (movement, that is) off-road. This was aptly demo'd on the off-road section of the Proving Grounds, where we took identical GX 470s over a severely rutted trail, one with the KDSS turned on and another with it off.

As you can see from the photos, the KDSS-assisted truck was able to keep all its tires in contact with the ground due to the greater suspension travel afforded by the system, while the one with KDSS switched off has a rear tire clawing at thin air.

Another benefit of KDSS is that it allows larger stabilizer bars for improved on-road handling via decreased body roll. So yes, sometimes you can have your cake and eat it, too.

Trying to Trip Up the Technology
For the Porsche event, we gathered at Barber Motorsports Park, home of the "Porsche Driving Experience" driving school. Here, the emphasis would be not just on dynamic safety, but also on how enjoyable an SUV (granted, a Porsche Cayenne) can be on a twisty road.

As with the Toyota event, much of the day was spent on exercises that showed off the effectiveness of the antilock brakes, and traction and stability control systems.

To show us how well the Cayenne's ABS works, Porsche had us perform a hard braking exercise on a surface that put the left-side tires on dry pavement and the rights on slippery pavement. This was essentially a worst-case braking scenario, given the widely different levels of grip for the right and left tires. Even so, mashing the pedal brought no drama as the vehicle stayed perfectly straight, even when we let go of the wheel (purely for demonstration purposes). The system brought the car to a smooth halt.

We also performed a panic swerve-and-stop to show how steering control is maintained via ABS. The ABS-disabled Cayenne slid straight ahead into the cones, while the ABS-enabled vehicle executed this "avoidance" maneuver cleanly.

The traction and stability control demonstrations involved accelerating hard on a soap-slicked section of pavement and performing emergency lane changes. The latter was even performed with the Cayenne towing a trailer with another Porsche on it! Once again, the near seamless operation of the systems impressed us, especially with the trailer in tow.

Sports Car Capability for an SUV
After all the safety system demonstrations, it was time to show off the Cayenne's sporting capability when pushed on the track. Driving both base (V6) and S (V8) versions of the Cayenne on the 15-turn, 2.4-mile track, it was clear that an SUV doesn't have to handle like a truck.

By the day's end, we were running pretty fast, and the feel behind the wheel inspired confidence. With its communicative and direct steering, lack of body roll and hunkered-down-to-the-road feel, the Cayenne was truly impressive when pressed.

What allows the Cayenne to be so composed under such extreme driving conditions? Unibody construction provides a lower center of gravity and less weight, a four-wheel independent (and well-sorted) suspension promises optimal tire-to-road contact, and, at higher speeds, intelligent aerodynamic design reduces lift, making the vehicle feel more buttoned down.

After the giddiness of blasting around the track subsided, one lasting impression remained: Provided that it is properly engineered, there's no reason an SUV can't be as dynamically safe and entertaining as a sport sedan. The ability to quickly maneuver around a potential accident can't be overvalued. And this is something one must strongly consider, especially when shopping for an SUV.

The Driver's Brain: Still the Most Important Computer
Even though advances in technology have made SUVs safer and even more entertaining on your favorite back-country roads, this doesn't mean caution can be thrown to the wind.

All the electronic wizardry in the world can't make up for poor or reckless driving. If you bomb into a corner on a slippery road, the stability control system probably won't be able to save you. Why? Because if there's little or no grip to be had, then the system has nothing to work with and you'll still end up in the weeds.

Whether you're buying new or used, we strongly recommend getting your next vehicle with as many of these features as possible, especially stability control. And we also encourage you to take note of driving conditions, your skill level and your vehicle's capabilities before you hit the road.

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