It all started with pumping the brakes. From the earliest days of the automobile, conventional wisdom has held that by “pumping” the brakes, applying them and releasing them rapidly, better control can be had under difficult conditions. Electronics takes that several steps further. Not only can the electronic controls pump the brakes faster, on the order of several times per second, the new systems can selectively apply each individual wheel brake, as required to maintain direction of travel. It must be remembered, though, that even with all these safety enhancements, the laws of physics cannot be overturned, so the driver has to exercise some judgment to begin with. It Started With ABS
The first of these systems to appear on vehicles was ABS, the Anti-skid Braking System. Since a wheel that is sliding, or skidding, cannot be steered, the ABS system allows the driver to maintain steering control. With this system, electronic sensors at each wheel monitor the rotation of the wheels. If a sensor notes that one wheel has stopped rotating, or is sliding, it quickly pulses the brakes to allow the wheel to continue turning, allowing the driver to control the direction of the vehicle. Traction control takes this one step further, by sensing if a wheel is spinning, or turning faster than the other wheel on the same axle. By selectively applying a single brake, and even reducing the throttle, the spinning wheel can be slowed and can maintain its grip on the road. Beyond that, the Electronic Stability Control system can correct under- and over-steer situations. In under-steer, the front of the vehicle tends to slide towards the outside of a curve. In over-steer, the rear of the vehicle tends to slide to the outside of the curve. A yaw sensor, combined with a steering sensor, can selectively brake the appropriate front or rear wheel, and additionally reduce the throttle, so that the vehicle continues in the direction the driver intends. All three of the above systems (ABS, Traction Control, and Electronic Stability Control) make up what Ford calls its AdvanceTrac system. Roll Stability Control
The final part of the package is Roll Stability Control. A gyroscopic sensor monitors the stability of the vehicle roughly 150 times per second. If it senses a potentially unstable situation, the system automatically engages AdvanceTrac to help keep all four wheels safely on the ground. In the past, drivers who were able to sense these vehicle motions and react to them quickly usually made their fortunes as racing drivers. Today, although the driver is still expected to drive responsibly, much of the mechanics of reacting to unstable driving conditions is taken over by the vehicle itself. AdvanceTrac with RSC, as installed on the Ford E-Series Extended Wagons, contributes to a safer environment for driver and passengers.