When you're going to tow a trailer, how can you tell if the trailer's antilock braking system (ABS) is working?
- Brake slowly.
- Slam on the brakes.
- Look for a light on the driver's side of the trailer. ✓
- Look for a light on the passenger side of the trailer.
Answer: C. Look for a light on the driver's side of the trailer.
You can tell by looking for a light on the driver's side of the trailer, visible in the tractor's mirror.
Why this is the answer
The handbook says trailers with ABS air brakes have an indicator you can see in the tractor's mirror. That warning light may be mounted on the front left side or the rear left side of the trailer, which is the driver's side. So the check is to look for that trailer ABS light on the driver's side, using the mirror. The handbook also says the ABS lights should be on when you first start the tractor, but the trailer indicator location is the key detail here.
Why the other answers are wrong
- A. Brake slowly. — Braking slowly is not described in the handbook as a way to check the trailer's ABS indicator.
- B. Slam on the brakes. — Slamming on the brakes is not the handbook's check for trailer ABS, and the handbook warns that forceful brake pressure can lock wheels and cause a skid or jackknife.
- D. Look for a light on the passenger side of the trailer. — The trailer ABS warning light is mounted on the left, driver's side of the trailer, not on the passenger side.
Remember it
Check the left side in your mirror: the trailer ABS light is on the driver's side.