CDL General Knowledge Test · CDL General Knowledge Test
Written by AI · Not yet reviewed by staffCDL General Knowledge Test Railroad Crossings and Mountain Driving Summary
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- About 5 of 50 CDL General Knowledge Test questions (9%)
Passive and active railroad crossings, how to cross safely, what to do if stuck on the tracks, choosing a safe downgrade speed and gear, brake fade, the downgrade braking method, and escape ramps.
📖 See Railroad Crossings and Mountain Driving concepts →Railroad Crossings and Mountain Driving: must-know points
- A typical tractor-trailer needs at least 14 seconds to clear a single track and more than 15 seconds for a double track.
- Do not shift gears while crossing railroad tracks.
- Pick a low gear before you start down a grade, and use engine braking as your main way to control speed.
- On a downgrade, brake until you are about 5 mph below your safe speed, then release.
Railroad Crossings and Mountain Driving: 8 sample questions
Question 1. What should you do about shifting gears while crossing railroad tracks?
- ① Do not shift gears while crossing the tracks
- ② Shift up halfway across to clear faster
- ③ Shift into neutral and coast across
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Answer: ① Do not shift gears while crossing the tracks
Key point: Never shift gears on the tracks
Do not shift gears while crossing railroad tracks. A missed shift could leave you stuck on the tracks. Choose a gear before you start across.
Wrong choices
- Shift up halfway across to clear faster: A missed shift could leave you stalled on the tracks.
- Shift into neutral and coast across: Coasting gives you less control.
Question 2. Your vehicle gets stuck on the railroad tracks. What should you do first?
- ① Stay in the cab and keep trying to start the engine
- ② Get out of the vehicle and away from the tracks
- ③ Walk along the tracks toward the train to warn it
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Answer: ② Get out of the vehicle and away from the tracks
Key point: Stuck on tracks: get out and away, then call
If you get stuck on the tracks, get out of the vehicle and away from the tracks right away. Then look for the emergency number on the signpost or signal housing, or call 911, and give the crossing's location (and the DOT number if posted).
Wrong choices
- Stay in the cab and keep trying to start the engine: If a train comes, you could be killed.
- Walk along the tracks toward the train to warn it: This puts you in danger. Use the emergency number instead.
Question 3. What is your main way to control speed on a long, steep downgrade?
- ① Light, steady pressure on the service brakes all the way down
- ② Shifting to neutral to let the vehicle roll
- ③ The braking effect of the engine in a low gear
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Answer: ③ The braking effect of the engine in a low gear
Key point: Engine braking controls downhill speed
Use the braking effect of the engine as your main way to control speed on a downgrade. It is strongest in lower gears near governed rpm. Save your brakes for when you need to slow or stop.
Wrong choices
- Light, steady pressure on the service brakes all the way down: This overheats the brakes and can cause brake fade.
- Shifting to neutral to let the vehicle roll: Neutral gives you no engine braking at all.
Question 4. What is brake fade?
- ① Brakes lose stopping power because they get too hot
- ② Brake lights grow dim over time
- ③ Brakes grab too hard when they are cold
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Answer: ① Brakes lose stopping power because they get too hot
Key point: Brake fade comes from overheating
When brakes get too hot, they start to fade: you must push harder and harder for the same stopping power. If you keep braking hard, they can fade until you cannot slow down at all.
Wrong choices
- Brake lights grow dim over time: Brake fade is about the brakes, not the lights.
- Brakes grab too hard when they are cold: Brake fade happens from too much heat.
Question 5. When should you select a low gear for a long downgrade?
- ① When the vehicle reaches the speed limit on the way down
- ② Only if the brakes start to smell hot
- ③ Before you start down the grade
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Answer: ③ Before you start down the grade
Key point: Pick the low gear before the downgrade
Shift to a low gear before you start down the grade. Once speed builds up, you may not be able to downshift at all, and you could lose all engine braking.
Wrong choices
- When the vehicle reaches the speed limit on the way down: By then you may not be able to get into a lower gear.
- Only if the brakes start to smell hot: That is a sign you waited too long.
Question 6. Your safe speed on a downgrade is 50 mph. Using the proper braking method, what should you do when you reach 50 mph?
- ① Brake firmly until you reach about 45 mph, then release the brakes
- ② Brake until you reach about 30 mph, then release
- ③ Hold light pressure on the brakes all the way down
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Answer: ① Brake firmly until you reach about 45 mph, then release the brakes
Key point: Downgrade: brake to 5 mph below safe speed
Proper downgrade braking (in the right low gear):
- When you reach your safe speed (50 mph), brake hard enough to feel a definite slowdown.
- When you reach about 5 mph below safe speed (45 mph), release the brakes. This takes about 3 seconds.
- When speed climbs back to 50 mph, repeat.
Wrong choices
- Brake until you reach about 30 mph, then release: Slowing this far takes long, hard braking and builds heat.
- Hold light pressure on the brakes all the way down: Steady light braking overheats the brakes.
Question 7. About how long does a typical tractor-trailer need to clear a single railroad track?
- ① About 8 seconds
- ② At least 14 seconds
- ③ About 4 seconds
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Answer: ② At least 14 seconds
Key point: Tractor-trailer: 14+ seconds to clear one track
A typical tractor-trailer takes at least 14 seconds to clear a single track and more than 15 seconds for a double track. Be sure you can get all the way across before you start.
Wrong choices
- About 8 seconds: It takes longer than this for a long, slow vehicle.
- About 4 seconds: This is far too short.
Question 8. Which of these vehicles is most likely to get stuck on a raised railroad crossing?
- ① A short straight truck with high ground clearance
- ② A low-slung unit such as a lowboy or car carrier
- ③ An empty flatbed with standard clearance
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Answer: ② A low-slung unit such as a lowboy or car carrier
Key point: Low-slung trailers can hang up on crossings
Low-slung units (lowboys, car carriers, moving vans, possum-belly livestock trailers) can get stuck on raised crossings. So can a single-axle tractor pulling a long trailer with its landing gear set for a tandem-axle tractor.
Wrong choices
- A short straight truck with high ground clearance: High ground clearance helps on raised crossings.
- An empty flatbed with standard clearance: A lowboy or car carrier is far more likely to hang up.
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