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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, 1999.
- Trucks and buses with hydraulic brakes and 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 5 mph.
If the yellow malfunction lamp stays on after the bulb check or goes on once you are underway, 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 will not allow you to drive faster, follow more closely or drive less carefully.
- ABS will not 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 turn.
- ABS will not necessarily shorten stopping distance. ABS will help maintain vehicle control but not always shorten stopping distance.
- ABS will not increase or decrease ultimate stopping power — ABS is an “add-on” to your normal brakes, not a replacement for them.
- ABS will not 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 will not 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.
Multiple-Choice Questions:
How will you know if your school bus is equipped with ABS?
- A yellow ABS sticker near the back emergency door
- Red ABS malfunction lamp on the instrument panel
- A yellow ABS malfunction light on the back of the bus below the brake lights
- Yellow ABS malfunction lamp on the instrument panel
When you drive a vehicle with ABS, which of the following is NOT the proper procedure?
- Use only the braking force necessary to stop safely and stay in control
- Pump the brakes if you are in an emergency braking situation
- As you slow down, monitor your bus and back off the brakes (if it is safe to do so) to 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.
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.
Which of the following are NOT true about ABS?
- ABS will not increase or decrease ultimate stopping power — ABS is an “add-on” to your normal brakes, not a replacement for them.
- ABS will compensate for bad brakes or poor brake maintenance.
- ABS will not necessarily shorten stopping distance. ABS will help maintain vehicle control but not always shorten stopping distance.
- ABS will not allow you to drive faster, follow more closely or drive less carefully.
- ABS will not allow you to drive faster, follow more closely or drive less carefully.
- ABS will not 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 turn.
- ABS will not necessarily shorten stopping distance. ABS will help maintain vehicle control but not always shorten stopping distance.
- ABS will not increase or decrease ultimate stopping power — ABS is an “add-on” to your normal brakes, not a replacement for them.
- ABS will not 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 will not 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.
How will you know if you've lost ABS function at one or more wheels?
- The yellow malfunction lamp goes off soon after starting the vehicle or goes off once you are underway
- The yellow malfunction lamp stays on after the bulb check or goes on once you are underway
- The yellow malfunction lamp blinks three times after the bulb check or blinks three times once you are underway
- The red malfunction lamp stays on after the bulb check or goes on once you are underway
If your ABS system malfunctions:
- You still have normal brake functions. Drive and brake as you always have
- You have reduced braking force. Slow your speeds and brake sooner
- Stop driving immediately. Do not move the vehicle until repairs are made
- Your wheels will easily lock up, even under relatively minor braking forces. Brake gently.
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