Traction Control vs. Stability Control Systems: What Is the Difference?
And is it ever safe to turn them off?
The difference between traction control and stability control is like the difference between a GED and a master's degree or PhD in vehicle safety. Stability control is just traction control with more vehicular education (computer programming) and better tools (a more powerful processor and more electronic sensors).
Clearly the anti-lock brake system, or ABS as we now know it, came first—on the 1971 Imperial. That same year, the Buick Riviera introduced MaxTrac, a primitive traction control system with no brake intervention, which instead compared transmission output speed with front wheel speed to detect spin and cut engine spark until the front and rear wheel speeds equalized. With no way to reduce fuel flowing through the carburetor, this reportedly led to some impressive backfires.
Stability control sort of debuted on the 1990 Japan-market Mitsubishi Diamante, variously referred to as active trace and traction control, then Active Skid and Traction Control (ASTC), but America's first taste of a system like the ones we know today arrived with help from Bosch on the 1995 Mercedes-Benz S600 coupe. Let's examine and compare the systems as they exist today.
What Is Traction Control?
This active safety feature was engineered to allow vehicles to make optimal use of the accelerative traction available on any given surface by measuring wheelspin, and then controlling it by using the anti-lock-braking system's hydraulic solenoids to apply braking pressure and/or by employing the engine's electronic throttle, fuel, or spark controls to trim power and slow a spinning wheel. These systems frequently offer the option of being switched off. The button to do this might be marked TC, TCL, or with an icon depicting the rear of a car above two backwards-S-shaped burnout marks. If your vehicle is equipped with both traction and stability control, they will almost certainly be controlled by the same button, which may then be labeled ESC, VSC, or with the icon. For a complete list of traction and stability control acronyms, scroll to the bottom of this article.
What Is Stability Control?
Modern stability control systems leverage all the hardware required by the traction control and anti-lock brake systems (a brake-pedal application sensor and wheel speed sensors at every wheel, plus a hydraulic valve body able to relieve or add pressure to the brake circuit for each wheel independently) and adds several new sensors. A steering wheel position sensor joins the brake and accelerator-pedal sensors to inform the system of the driver's intended path and speed. A yaw sensor measures how much the vehicle is rotating around its vertical axis (what you experience as a skid or spin), and a three-axis accelerometer module detects both lateral and longitudinal acceleration, as well as any angular slope the vehicle is driving on. Consulting all these sensors, a more powerful computer then compares the vehicle's actual motion with the driver's intention. If the two don't match, the system applies individual wheel brakes (as well as engine controls, if necessary) to bring the vehicle's path into alignment with the driver's intention. Note that because stability control became mandatory in the U.S. in 2012, all new passenger vehicles are equipped with the holy trinity of driver-assist systems: ABS, traction, and stability control.
How Does Stability Control Change the Vehicle's Path?
If you've ever gone canoeing, kayaking, or whitewater rafting, you've probably steered a boat by back paddling on the side that you want to steer toward. Stability control does the same thing—adding brake pressure to one side of the car to gently steer it in that direction, with varying results depending on whether and how much the front or rear brakes are applied. Remember, the driver has already dialed in a desired amount of steering, so if the car isn't reacting as it should, then reduced traction, extreme winds, or some other external force is causing the path to deviate, so simply ordering the electric steering assist to steer more is unlikely to achieve the desired effect. A deft stability control system does its work without the driver noticing, except perhaps for the blinking stability-control lamp that indicates the system is working.
How Do ABS, Traction Control and Stability Control Work Together?
The systems are completely integrated, so it's impossible to have stability control or traction control without ABS. The anti-lock braking system's hydraulic valve block enables the wheel-speed regulation required to limit wheelspin for traction control and for stability control to regulate the vehicle's path. Some vehicles allow drivers to disable or dial back the effectiveness of the systems. Traction-control off buttons are most prevalent, stability off-buttons are less so (and when they exist they can be nested in screen menus and they seldom turn the system completely off, as we frequently find in our Figure Eight testing). As noted, these systems also share the same button as well. Note that not since the B3 ('86-'92) Audi 80/90 has an ABS-off switch been offered.
My Stability Control Offers Settings—Which Is Best?
Some performance vehicles offer different settings (like the Chevrolet Corvette, many Cadillac V-cars, or any BMW M car) tailored to more aggressive driving situations. These sometimes offer so many settings that owners' forums are probably better equipped to answer this question. Off-road-oriented vehicles that provide different terrain modes tailor the level of stability control intervention in each to suit the different terrains, so simply setting this mode to match the terrain you're covering is best. Otherwise, John & Jane Q Public are best advised to leave those traction and stability control buttons alone on public roads. Performance-mode settings are often accessible only from deep inside infotainment-system menu trees or by pressing and holding a button for many seconds. They tend to make the system more permissive of neutral slides or even some degree of oversteer drifts. If you've had high-performance driver training courses and you're planning to drive your car on a closed course with safety guard rails and so forth (and are prepared for the insurance hit if something goes badly wrong), engaging these settings may indeed make your car much more fun to drive. Note that many (but not all) of these systems revert to full safety-net mode if you touch or stab the brakes in the middle of a slide.
When Should I Turn Off Traction Control?
If you're in a normal car with no terrain modes that becomes slightly stuck in sand or snow because your system kills the power at the first hint of wheelspin, switching off the traction control portion of the system can allow the wheels to spin enough to "burn down" through snow or sand to a grippier surface below and get the vehicle moving again.
When Should I Turn Off Stability Control?
Have you won an SCCA title or finished a LeMans race? Are you helping Kim Reynolds measure MotorTrend Figure Eight performance at our test facility? If you answered "no" to all of these, then maybe never, which is why manufacturers generally make it difficult to access the "off" mode, so nobody accidentally turns it off. We can't recommend ever turning stability control completely off on a public road, but exceptional drivers seeking to fully explore the limits of their high-performance vehicle on a closed road or track may find the "off" setting valuable.
What Causes the Stability Control Light to Come on?
Stability control is a safety system, so its functionality is continuously monitored by the onboard diagnostic electronics. That light comes when the system is either switched off, switched to a lower level of sensitivity, or suffers any sort of fault (some off-road terrain modes reduce the system's effectiveness enough to illuminate the lamp when in those modes). So, if you haven't touched a switch and it comes on, you probably have a system fault. The most common of these are sensor malfunctions, and the sensors that are first to go are those mounted out in the elements, like the wheel-speed sensors. These can be knocked out of alignment or damaged by road hazards or become corroded. The light will oftentimes flash when the traction and/or stability control system is actively intervening to bring the car back under control.
What Are Other Names for Stability Control?
Here is a list of the names various manufacturers use for their stability control systems around the world:
Acura: Vehicle Stability Assist (VSA) (formerly CSL 4-Drive TCS)
Alfa Romeo: Vehicle Dynamic Control (VDC)
Audi: Electronic Stability Program (ESP)
Bentley: Electronic Stability Program (ESP)
BMW: Co-engineering partner and inventor with Robert Bosch GmbH and Continental (TEVES) Dynamic Stability Control (DSC) (including Dynamic Traction Control)
Bugatti: Electronic Stability Program (ESP)
Cadillac: StabiliTrak and StabiliTrak3.0 with Active Front Steering (AFS)
Chevrolet: StabiliTrak and Active Handling (Corvette & Camaro only)
Chrysler: Electronic Stability Program (ESP)
Dodge: Electronic Stability Program (ESP)
Fiat: Electronic Stability Control (ESC) and Vehicle Dynamic Control (VDC)
Ferrari: Controllo Stabilità (CST)
Ford: AdvanceTrac with Roll Stability Control (RSC) and Interactive Vehicle Dynamics (IVD) and Electronic Stability Program (ESP)
General Motors: StabiliTrak
Honda: Vehicle Stability Assist (VSA) (formerly CSL 4-Drive TCS)
Hyundai: Electronic Stability Program (ESP), Electronic Stability Control (ESC) and Vehicle Stability Assist (VSA)
Infiniti: Vehicle Dynamic Control (VDC)
Jaguar: Dynamic Stability Control (DSC), and Automatic Stability Control (ASC)
Jeep: Electronic Stability Program (ESP)
Kia: Electronic Stability Control (ESC) and Electronic Stability Program (ESP)
Lamborghini: Electronic Stability Program (ESP)
Land Rover: Dynamic Stability Control (DSC)
Lexus: Vehicle Dynamics Integrated Management (VDIM) with Vehicle Stability Control (VSC)
Maserati: Maserati Stability Program (MSP)
Mazda: Dynamic Stability Control (DSC) (including Dynamic Traction Control)
Mercedes-Benz co-inventor with Robert Bosch GmbH: Electronic Stability Program (ESP)
Mini: Dynamic Stability Control
Mitsubishi: Active Skid and Traction Control MULTIMODE and Active Stability Control (ASC)
Nissan: Vehicle Dynamic Control (VDC)
Porsche: Porsche Stability Management (PSM)
Subaru: Vehicle Dynamics Control (VDC)
Toyota: Vehicle Stability Control (VSC) and Vehicle Dynamics Integrated Management (VDIM)
Tesla: Electronic Stability Control (ESC)
Volvo: Dynamic Stability and Traction Control (DSTC)
Volkswagen: Electronic Stability Program (ESP)