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GM Brings Safety Advantages Of Stability Enhancement

FOR RELEASE: March 14, 2002

GM Brings Safety Advantages Of Stability Enhancement To More Sport Utility Models

Detroit, MI- GM is the leader in bringing the safety advantages of vehicle stability enhancement to more people, in more market segments than any other automaker. Furthering this leadership, GM will now make this important active safety technology available on more sport utility models. Beginning in the 2003 model year, StabiliTrak will be available on all Chevrolet and GMC full-size utilities with the 5.3-liter V8 engine.

A four-channel StabiliTrak stability enhancement system will be available on the 1500 series Chevrolet Tahoe, Suburban, Avalanche, GMC Yukon, Yukon Denali, Yukon XL and Yukon Denali XL, available in some combinations of two-wheel drive, 4X4 and all-wheel drive models. Previously, a two-channel StabiliTrak was exclusive in GM full-size trucks on the Cadillac Escalade and Escalade EXT.

"We have a history of leveraging our vast size and technical resources to bring safety features to our customers," said Terry Woychowski, GM's full-size truck Chief Engineer. "With StabiliTrak, we're able to capitalize on our large production volumes, and make the safety benefits of this technology available in more vehicles."

Since the introduction of StabiliTrak on three 1997 Cadillac models, GM has continued to refine its stability enhancement systems and expand them to other model lines. Overall, GM has delivered more than 600,000 vehicles equipped with stability enhancement systems since the introduction of StabiliTrak.

In addition to the expanded availability of the StabiliTrak system in GM full-size sport utility vehicles, the system has also been refined for 2003. The new four channel StabiliTrak operates in harmony with the antilock brake and traction control systems to selectively apply any of the four brakes in an effort to help the driver counteract and diffuse potentially dangerous handling situations, such as severe oversteer or understeer. This four-channel StabiliTrak system is designed to optimize vehicle contact with the road surface.

Driver benefits

Stability enhancement helps a driver maintain control, increasing the odds of avoiding a crash. While loss of control is most likely to happen on ice, snow or wet pavement, these systems improve stability on a variety of surfaces and speeds, as well as in emergency lane changes or avoidance maneuvers.

"Stability enhancement increases the ability of the driver to control the truck," Woychowski said. "GM's systems are designed to feel natural and to provide smooth, transparent assistance only when it is necessary. In most cases, the driver doesn't know that the system has been activated, except for an indicator light on the instrument panel."

As impressive as these systems are, it is important to remember that they cannot override physics. There will be circumstances in which this technology will not be able to overcome gross driver error or other road hazards.

Evolution

Today's stability enhancement systems are the result of an ongoing evolution in chassis controls at GM that began with the introduction of antilock braking systems (ABS) on the 1986 Corvette. The evolution continued with innovations such as electronic traction control, electronic throttle controls, variable assist steering, and variable suspension systems.

The integration of these chassis systems enabled GM to create its first stability enhancement system, StabiliTrak, by adding two additional sensors - measuring yaw rate and lateral acceleration - along with an updated steering angle sensor and new software. StabiliTrak debuted on three 1997 Cadillac models - Seville Touring Sedan, Eldorado Touring Coupe and DeVille Concours.

With StabiliTrak, a digital steering angle sensor precisely measures the driver's intended path. The yaw of the vehicle body - the rate at which it is actually turning - is measured by a solid-state yaw rate sensor that uses a pair of tiny ceramic tuning forks to convert the turning motion of the body into a signal the computer can read.

A third sensor, measuring lateral acceleration, helps the computer determine whether available traction has been exceeded. Information is also gathered on vehicle speed. This allows the computer to fine-tune corrections to match the cornering speeds and available traction.

The same computer that operates the anti-lock brakes and traction control system also operates the stability enhancement system. Using these various inputs, StabiliTrak compares the driver's intended path with the vehicle's actual path, and adjusts the brake and throttle to help bring the vehicle back under control.

Real world maneuvers, such as an emergency lane change, may involve several quick steering inputs. Throughout these maneuvers, the stability enhancement system calculates the desired direction of travel and adjusts the individual brakes and throttle in fractions of a second to optimize stability and control.

The system also enhances the stability of the vehicle where the yaw rate of the vehicle doesn't correspond with the steering inputs from the driver. If the vehicle is traveling in a straight line and starts to skid because of snow, ice, gravel or standing water, StabiliTrak gently applies the correct corner brake to maintain the driver's intended path. If the driver enters a corner or off-ramp too quickly, the system helps the driver bring the vehicle under control in a safe, predictable manner.

"Stability enhancement is one of the most significant active safety advancements since antilock brakes," Woychowski said. "GM is committed to maintaining its leadership position in trucks, and in making these innovative safety technologies available, we know our trucks will be carefully considered by people in the market for a truck."

FACT SHEET

StabiliTrak Technology Overview:

StabiliTrak is a vehicle stability enhancement system (VSES) that improves vehicle stability on all road surfaces at all speeds, particularly on slick surfaces or during emergency maneuvers.

  • Maximizes handling and braking dynamics by using a combination of systems and sensors including ABS, traction control, electronic suspension.
  • An array of sensors continually monitor the driver's intended vehicle path, measuring steering angle, wheel speed, brake pressure, lateral acceleration, longitudinal acceleration and yaw rate. This information is provided to an electronic control module that continually monitors vehicle dynamics and is programmed for intervention thresholds.
  • The system intervenes when it senses one or more of the wheels slipping, loss of lateral traction (side slip), or detects under-steer (snow-plowing) or over-steer (fish-tailing) (refer to presentation graphics). Automatically, the system adjusts engine torque or brake pressure at individual wheels to help to steer the vehicle in the intended path.

Technology Features/Benefits:

Situations in which stability enhancement can assist the driver include:

  • Helping move the vehicle where the driver points it.
  • Helping control or minimize fishtailing on snowy or wet road.
  • Assisting the driver in maintaining control while cornering on wet roads or uneven road surfaces such as puddles or snow piles.
  • Improving the stability and steerability of the vehicle while driving on snowy or wet roads.
  • Helping the vehicle respond more naturally and predictably to the driver's steering commands, even in avoidance maneuvers.

Market Coverage:

In North America during the 2002 model year, GM offers stability enhancement systems on 11 products, and by the 2006 model year, this feature will be available on many more of the vehicles in our portfolio.

For 2002, GM offers stability enhancement systems in the following segments:

  • Performance: Chevrolet Corvette (Active Handling)
  • Family sedan: Oldsmobile Intrigue (Precision Control System)
  • Large sedan: Pontiac Bonneville (StabiliTrak), Oldsmobile Aurora (Precision Control System), Buick LeSabre (StabiliTrak), Buick Park Avenue (StabiliTrak)
  • Luxury coupe: Cadillac Eldorado (StabiliTrak)
  • Luxury sedan: Cadillac DeVille (StabiliTrak), Cadillac Seville (StabiliTrak)
  • Luxury SUV: Cadillac Escalade (StabiliTrak)
  • Luxury sport-utility truck: Cadillac Escalade EXT (StabiliTrak)
  • New for '03 Full-Size Sport Utility Vehicles, Utility Truck: Chevrolet Tahoe, Suburban, Avalanche, GMC Yukon, Yukon XL, Yukon Denali and Yukon Denali XL (all 1500 series)