Iowa CDL — General Knowledge practice
Iowa CDL — General Knowledge: Signals & Pavement Markings practice test
How to read traffic signals, lane lines, and pavement markings — including yellow and white lines, arrows, and flashing lights.
Content reviewed against official driver handbooks · August 12, 2026
13 questions · pass with 10 correct. You get instant feedback and an explanation after every answer.
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12 sample Signals & Pavement Markings questions with the correct answer, a short explanation, and the official handbook reference. Read through them, then take the quiz above.
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1. Right after you start the engine, how should the coolant temperature gauge behave?
Correct answer: Begin a gradual rise toward the normal operating range
Coolant temperature, like engine oil temperature, should rise gradually to its normal range after start-up.
Source: Iowa Commercial Driver's License Manual — Section 2.1.5, Seven-step Inspection Method
2. After you start the engine on an air brake vehicle, how quickly should pressure build from 50 to 90 psi?
Correct answer: Within 3 minutes
When you read the gauges, pressure should rise from 50 psi to 90 psi in 3 minutes or less, then keep building to governor cutout.
Source: Iowa Commercial Driver's License Manual — Section 2.1.5, Seven-step Inspection Method
3. Which brake light behavior must you confirm during the lights operations check?
Correct answer: The brake lights come on when the brakes are applied and go off when they are released
Part of the lights check is confirming that the brake lights illuminate when you press the brakes and shut off when you let go.
Source: Iowa Commercial Driver's License Manual — Section 11.4, Lights Operations Check (All Vehicles)
4. You forget to tell the examiner about one of the lights during the lights operations check. What happens?
Correct answer: You get no credit for that light
You must tell the examiner exactly which lights to watch as you switch them on, with your window down and speaking loudly enough. Any light you leave out earns no credit.
Source: Iowa Commercial Driver's License Manual — Section 11.4, Lights Operations Check (All Vehicles)
5. As you approach railroad tracks, what does Iowa's manual suggest doing inside the cab?
Correct answer: Lower the windows, shut off music, and cut out distractions
Iowa's railroad page advises eliminating distractions, rolling your windows down, and switching your music off as you near the tracks, so you have the best chance of hearing a train.
Source: Iowa Commercial Driver's License Manual — Railroad Crossings
6. During the leakage test of Iowa's air brake check, how much may pressure drop in one minute on a combination vehicle once the gauge stabilizes?
Correct answer: No more than 4 psi
With the foot brake held for one minute after the gauge settles, a single vehicle should lose no more than 3 psi and a combination vehicle no more than 4 psi.
Source: Iowa Commercial Driver's License Manual — Preparing for Your Brake Check
7. On the road test, what should you check first right after you complete a turn?
Correct answer: That your turn signal is off
Once the turn is done, make sure the signal is canceled, then get up to traffic speed, signal, and move into the right-most lane when it's safe, checking mirrors and traffic.
Source: Iowa Commercial Driver's License Manual — Section 13.1.1, Turns
8. During the air brake check, at about what pressure should the governor cut out?
Correct answer: About 120 to 140 psi, or the manufacturer's level
Build the air pressure up to governor cutout, roughly 120 to 140 psi or whatever the manufacturer specifies, and identify the cutout pressure for your vehicle.
Source: Iowa Commercial Driver's License Manual — Preparing for Your Brake Check
9. In Step 4 of the seven-step inspection, which lights do you switch on before getting out of the vehicle?
Correct answer: The low-beam headlights and the four-way flashers
With the parking brake set, the engine off, and the key in your possession, turn on the low beams and four-way flashers, then get out and check them from the front.
Source: Iowa Commercial Driver's License Manual — Section 2.1.5, Seven-step Inspection Method
10. As you fan down the air pressure during Iowa's brake check, which three low air warning devices should activate?
Correct answer: A buzzer, a warning light, and a flag
The low air warning devices are a buzzer, a light, and a flag. They should come on before pressure falls below 55 psi, or the level the manufacturer specifies.
Source: Iowa Commercial Driver's License Manual — Preparing for Your Brake Check
11. On your walk-around, you notice that the forward-facing turn signal on the right front of your truck glows red. Is that acceptable?
Correct answer: No; forward-facing turn signals should be amber or white
Turn signals that face forward should be clean, working, and amber or white. Red belongs at the rear, where turn signals may be red, yellow, or amber.
Source: Iowa Commercial Driver's License Manual — Section 2.1.5, Seven-step Inspection Method
12. During the walk-around, how do you check that the high beams work?
Correct answer: Push the dimmer switch and check the front of the vehicle
At the front of the vehicle in Step 5, confirm the low beams and both flashers, then push the dimmer switch to make sure the high beams come on.
Source: Iowa Commercial Driver's License Manual — Section 2.1.5, Seven-step Inspection Method
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