• As you slow down, monitor your tractor and trailer and back off the brakes (if it is safe to do so) to stay in control. 

There is only one exception to this procedure. If you drive a straight truck or combination with working ABS on all axles, in an emergency stop, you can fully apply the brakes. 

## 2.18.7 – Braking If ABS Is Not Working 

Without ABS you still have normal brake functions. Drive and brake as you always have. 

Vehicles with ABS have yellow malfunction lamps to tell you if something isn’t working. 

As a system check on newer vehicles, the malfunction lamp comes on at start-up for a bulb check and then goes out quickly. On older systems, the lamp could stay on until you are driving over five mph. 

If the lamp stays on after the bulb check, or goes on once you are under way, you may have lost ABS control on one or more wheels. 

Remember, if your ABS malfunctions, you still have regular brakes. Drive normally, but get the system serviced soon. 

## 2.18.8 – Safety Reminders 

• ABS won’t allow you to drive faster, follow more closely, or drive less carefully. 

• ABS won’t prevent power or turning skids–ABS should prevent brake-induced skids or jackknifes, but not those caused by spinning the drive wheels or going too fast in a turn. 

• ABS won’t necessarily shorten stopping distance. ABS will help maintain vehicle control, but not always shorten stopping distance. 

• ABS won’t increase or decrease ultimate stopping power–ABS is an “add-on” to your normal brakes, not a replacement for them. 

• ABS won’t change the way you normally brake. Under normal brake conditions, your vehicle will stop as it always stopped. ABS only comes into play when a wheel would normally have locked up because of over braking. 

• ABS won’t compensate for bad brakes or poor brake maintenance. 

• Remember: The best vehicle safety feature is still a safe driver. 

• Remember: Drive so you never need to use your ABS. 

• Remember: If you need it, ABS could help to prevent a serious crash. 

## 2.19 – Skid Control and Recovery 

A skid happens whenever the tires lose their grip on the road. This is caused in one of four ways: 

Over-braking. Braking too hard and locking up the wheels. Skids also can occur when using the speed retarder when the road is slippery. 

Over-steering. Turning the wheels more sharply than the vehicle can turn. 

Over-acceleration. Supplying too much power to the drive wheels, causing them to spin. 

Driving Too Fast. Most serious skids result from driving too fast for road conditions. Drivers who adjust their driving to conditions don't over- accelerate and don't have to over-brake or over- steer from too much speed. 

## 2.19.1 – Drive-wheel Skids 

By far the most common skid is one in which the rear wheels lose traction through excessive braking or acceleration. Skids caused by acceleration usually happen on ice or snow. Taking your foot off the accelerator can easily stop them. (If it is very slippery, push the clutch in. Otherwise, the engine can keep the wheels from rolling freely and regaining traction.) 

Rear wheel braking skids occur when the rear drive wheels lock. Because locked wheels have less traction than rolling wheels, the rear wheels usually slide sideways in an attempt to "catch up" with the front wheels. In a bus or straight truck, the vehicle will slide sideways in a "spin out." With vehicles towing trailers, a drive-wheel skid can let the trailer push the towing vehicle sideways, causing a sudden jackknife. See Figure 2.19. 

