Iowa CDL — General Knowledge practice
Iowa CDL — General Knowledge: Road Signs practice test
Learn the shapes, colors, and meanings of regulatory, warning, and guide signs — from stop and yield to construction and school-zone signs.
Content reviewed against official driver handbooks · August 12, 2026
14 questions · pass with 11 correct. You get instant feedback and an explanation after every answer.
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12 sample Road Signs 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. During the inspection test on a school bus, what must you confirm about the stop arm besides it being firmly mounted?
Correct answer: That it extends fully and that its lights and dashboard indicator work
For the stop arm, check that it is securely mounted with no damaged parts, extends all the way, and that its lights and the dash indicator operate.
Source: Iowa Commercial Driver's License Manual — Section 11.3, School Bus Only
2. A crossing gate is down and its lights are flashing, but you can't see a train. May you drive around the gate?
Correct answer: No; a train is coming even if it isn't visible yet, and going around lowered gates is illegal
Lowered gates and flashing lights mean a train is approaching, seen or not. Wait until the lights stop and the gates rise; driving around them is both illegal and dangerous.
Source: Iowa Commercial Driver's License Manual — Railroad Crossings, Know the Signs and Signals
3. Reflective tape is required on trailers. Which other vehicle does the manual say some jurisdictions may also require it on?
Correct answer: School buses
The inspection guidance says reflective tape is required only for trailers, while noting that some jurisdictions' laws may require it on school buses as well.
Source: Iowa Commercial Driver's License Manual — Section 11.6.2, Trailers Only
4. What colors is the Emergency Notification System (ENS) sign posted at railroad crossings?
Correct answer: Blue and white
The ENS sign is blue and white. It gives a phone number to call and the crossing's ID number to read to the dispatcher.
Source: Iowa Commercial Driver's License Manual — Railroad Crossings, Know the Signs and Signals
5. Why do rail cars carry reflective stripes?
Correct answer: To make them easier to see at night and in rain, snow, or fog
Reflective stripes help rail cars stand out in the dark and in poor visibility, so watch for them when weather makes a train hard to spot.
Source: Iowa Commercial Driver's License Manual — Railroad Crossings, Make Safe Choices
6. What does the manual require of the 'Emergency Exit' marking on a bus's emergency door?
Correct answer: It must be clearly visible
The marking that labels a bus's emergency door has to be easy to see. Never drive with an emergency exit door or window open, and make sure any red emergency door light works.
Source: Iowa Commercial Driver's License Manual — Section 4.1.3, Bus Interior
7. Besides a vehicle stuck on the tracks, which of these can you report by calling the number on an ENS sign?
Correct answer: A damaged crossing signal or debris on the tracks
Use the ENS number to report anything on the rails, such as people, stalled vehicles, or debris, as well as broken signs or signals and blocked sight lines at the crossing.
Source: Iowa Commercial Driver's License Manual — Railroad Crossings, Know the Signs and Signals
8. A shipper hands you placard-level cartons of matches. On the manual's hazard class table, which class name fits that cargo?
Correct answer: Flammable Solids
The table lists matches and fuses under Class 4, Flammable Solids.
Source: Iowa Commercial Driver's License Manual — Section 2.23.3, Lists of Regulated Products (Figure 2.25, Hazard Class Definitions)
9. Why should you call the number on the ENS sign at the crossing where you actually are, instead of a number from a different crossing?
Correct answer: Each ENS sign carries its own phone number and location ID
Every ENS sign has its own phone number and crossing ID number, which lets the railroad know exactly which crossing has the problem.
Source: Iowa Commercial Driver's License Manual — Railroad Crossings, Know the Signs and Signals
10. As you approach a railroad crossing, which sign are you usually going to see first?
Correct answer: The advance warning sign
The advance warning sign is typically the first one on the approach. It's your cue to reduce speed, watch and listen for a train, and be ready to stop.
Source: Iowa Commercial Driver's License Manual — Railroad Crossings, Know the Signs and Signals
11. What does a 'low ground clearance' railroad crossing sign warn you about?
Correct answer: A raised crossing where low-slung vehicles such as lowboys, buses, or trailers could get hung up
It marks a raised crossing. Vehicles that ride close to the pavement can bottom out on the rails, so wait until you're sure your rig can get over without hanging up.
Source: Iowa Commercial Driver's License Manual — Railroad Crossings, Know the Signs and Signals
12. You notice the signals at a crossing seem to be malfunctioning, or you see damage to the track. What does the manual tell you to do?
Correct answer: Call the number posted at the crossing to notify the railroad
Crossings post the railroad's name and an emergency number. Use it to report a signal malfunction, a stalled vehicle, an obstruction, or track damage.
Source: Iowa Commercial Driver's License Manual — Railroad Crossings
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