Combination Vehicles Practice Test Flashcards

What is a 'bobtail' tractor?

Answer: A tractor operating without a trailer attached

A bobtail is a tractor with no trailer, which can be surprisingly hard to stop and prone to skidding.

When the trailer wheels lock up on a combination vehicle, the most likely result is:

Answer: Trailer jackknife (trailer swings out)

Locked trailer wheels cause the trailer to swing out, known as a trailer jackknife.

If the drive wheels (tractor) begin to skid in a combination vehicle, you should:

Answer: Release the brakes to let the wheels roll again

Releasing the brakes lets the wheels roll and regain traction to recover from a drive-wheel skid.

The trailer hand valve (trolley valve) should be used:

Answer: Only to test the trailer brakes, never for parking

The hand valve should only be used to test trailer brakes; using it to hold a parked vehicle is dangerous and it can apply trailer brakes alone and cause a skid in driving.

When inspecting the landing gear during a combination vehicle check, you should verify it is:

Answer: Fully raised and the crank handle secured

The landing gear must be fully raised with the crank handle secured so it doesn't drag or interfere while driving.

Why must you check that there are no signs of leaking fluids or air between the coupled units?

Answer: Leaks can indicate failing seals or air lines that could cause brake or coupling failure

Fluid or air leaks signal failing components that could lead to brake loss or other dangerous failures.

How does the stopping distance of a heavily loaded combination vehicle compare to that of a passenger car at the same speed?

Answer: It is much longer due to greater weight and length

Loaded combination vehicles need much greater stopping distance because of their weight, length, and momentum.