Why is it dangerous to depend only on the trailer hand valve to slow a combination vehicle in an emergency?

Pick an answer

1. Using it alone can cause the trailer to skid or jackknife because it doesn't apply the tractor's brakes
2. It has no effect on braking at all
3. It only works below 10 mph
4. It applies more force than the foot pedal and stops the vehicle too quickly for the traffic following close behind

Correct!

Not quite. The correct answer is highlighted.