Traffic Signs & Signals — Illinois
Illinois CDL practice test: 447 free practice questions (Based on the official driver handbook). The official format is not yet verified; check the official site before your test. Traffic Signs & Signals: 3 questions.
Regulatory, warning and guide signs, plus traffic light and pavement marking questions.
This topic page is still being reviewed against the official handbook. Until review is finished it is hidden from search engines.
| Topic / Metric | Value |
|---|---|
| Topic | Traffic Signs & Signals |
| License test | Illinois CDL permit (CLP) knowledge tests |
| Topic questions | 3 (1% of 447 total) |
| Review status | This topic page is still being reviewed against the official handbook. Until review is finished it is hidden from search engines. |
Official handbook
Not yet verified
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Questions (3)
1. What does the trailer air supply control look like?
- It is a square blue knob.
- It is a triangular yellow knob.
- It is an eight-sided red knob. ✓
- It is a circular orange knob.
Answer: C. It is an eight-sided red knob.
The trailer air supply control on newer vehicles is a red eight-sided knob. The handbook describes the trailer air supply control in the cab, which operates the tractor protection valve. On newer vehicles it is a red knob with eight sides. You push it in to send air to the trailer and pull it out to cut the air off and apply the trailer emergency brakes. The same knob pops out on its own when air pressure falls to roughly 20 to 45 psi, closing the tractor protection valve. Older vehicles may instead have a lever rather than a knob.
2. Which of the following is not a warning sign of fatigue?
- Frequent blinking
- Rubbing your eyes
- Missing exits or traffic signs
- Staying within your lane ✓
Answer: D. Staying within your lane
3. When approaching a drawbridge that is controlled by a traffic signal, you may proceed:
- If the signal is green. ✓
- Only after coming to a complete stop 50 feet before the bridge.
- Only if other vehicles are also proceeding.
- Only after getting out of your vehicle to check the conditions.
Answer: A. If the signal is green.
You may proceed when the drawbridge's traffic signal is green. The handbook separates drawbridges with signals or an attendant from those without them. At a bridge with no signal light or traffic control attendant, you must stop at least 50 feet before the draw and check that it is fully closed. When a traffic light shows green, the rule changes: you do not have to stop, but you still must slow down and confirm it is safe. That matches proceeding on a green signal.
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Source
Last checked: 2026-10-17 · Verified from official source
Updated: · Based on the official driver handbook