10.6 Antilock Braking Systems

10.6.1 Vehicles Required to Have Antilock Braking Systems

The Department of Transportation requires that antilock braking systems be on:

  • Air brakes vehicles, (trucks, buses, trailers and converter dollies) built on or after March 1, 1998.
  • Hydraulically braked trucks and buses with a gross vehicle weight rating of 10,000 lbs or more built on or after March 1, 1999.

Many buses built before these dates have been voluntarily equipped with ABS.

Your school bus will have a yellow ABS malfunction lamp on the instrument panel if it is equipped with ABS.

10.6.2 How ABS Helps You

When you brake hard on slippery surfaces in a vehicle without ABS, your wheels may lock up. When your steering wheels lock up, you lose steering control. When your other wheels lock up, you may skid or even spin the vehicle.

ABS helps you avoid wheel lock up and main­tain control. You may or may not be able to stop faster with ABS, but you should be able to steer around an obstacle while braking, and avoid skids caused by over braking.

10.6.3 Braking with ABS

When you drive a vehicle with ABS, you should brake as you always have. In other words:

  • Use only the braking force necessary to stop safely and stay in control.
  • Brake the same way, regardless of whether you have ABS on the bus. However, in emer­gency braking, do not pump the brakes on a bus with ABS.
  • As you slow down, monitor your bus and back off the brakes (if it is safe to do so) to stay in control.

10.6.4 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 is not working.

The yellow ABS malfunction lamp is on the bus's instrument panel.

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 at one or more wheels.

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

10.6.5 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 but not those caused by spinning the drive wheels or going too fast in a tum.
  • 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.