Speed Limits & Following Distance — 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. Speed Limits & Following Distance: 23 questions.
Posted speed limits, school and construction zones, stopping and following distance.
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 | Speed Limits & Following Distance |
| License test | Illinois CDL permit (CLP) knowledge tests |
| Topic questions | 23 (5% 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 (23)
1. To prevent a trailer from rolling over, you should:
- Speed up when nearing a corner.
- Make sudden steering moves.
- Take on-ramps faster than the posted speed limit.
- Drive slowly around corners. ✓
Answer: D. Drive slowly around corners.
To prevent a trailer from rolling over, drive slowly around corners. The handbook says rollovers happen when you turn too fast. For trailers, it advises you to steer gently and go slowly around corners, ramps, off ramps, and curves. A speed that is safe for a straight truck or a single trailer may be too fast for doubles or triples. Slowing down around a corner reduces the chance that turning speed will tip the trailer. The passage ties rollover prevention directly to gentle steering and lower speed in turns.
2. When using road speed to know when to switch gears, you should:
- Learn what speeds each gear is good for and shift up when necessary. ✓
- Watch other vehicles and try to keep pace.
- Watch other trucks and shift when they shift.
- Use the speed limit as a guide.
Answer: A. Learn what speeds each gear is good for and shift up when necessary.
Learn what speeds each gear is good for, then use your speedometer to know when to shift up. The handbook lists two ways to know when to shift: engine speed or road speed. For the road speed method, it says to learn the speeds each gear is good for and use the speedometer to know when to shift up. That is a general skill tied to your own vehicle and gears, not something you pick up by copying traffic around you.
3. How does doubling your speed from 20 mph to 40 mph affect your vehicle's braking distance?
- It stays about the same.
- It increases slightly.
- It doubles.
- It quadruples. ✓
Answer: D. It quadruples.
Doubling your speed from 20 mph to 40 mph makes the braking distance four times longer. The handbook's stopping-distance figure says that when you go from 20 to 40 mph, the impact is four times greater and the braking distance is also four times longer. So the increase is not a small change or just double; it is four times the distance. The same passage shows the pattern continues at higher speeds, which reinforces that speed has a strong effect on braking distance.
4. Which condition increases a tank's stopping distance?
- A dry road
- A loaded tank
- An empty tank ✓
- Cloudy weather
Answer: C. An empty tank
An empty tank increases a tank vehicle's stopping distance; the handbook says empty tank vehicles may take longer to stop than full ones. The tank vehicle section on safe driving rules addresses stopping distance directly. It says empty tank vehicles may need more room to stop than full ones, which makes the empty tank the condition that increases stopping distance. The same passage warns that wet roads double normal stopping distance, but wet roads are not among the choices. It also advises smooth braking and steady brake pressure because liquid surge affects control. The provided passages do not link a dry road, a loaded tank, or cloudy weather to longer stopping distance.
5. If being tailgated, you should:
- Drive in the left lane.
- Drive in the right lane. ✓
- Speed up.
- Drive on the shoulder.
Answer: B. Drive in the right lane.
If you are being tailgated, drive in the right lane. The handbook says a heavy vehicle that cannot keep up with traffic should stay in the right lane if it can, and it notes tailgating often happens when you are traveling slowly. It also says to increase the space in front of you so you can avoid sudden speed or direction changes and so the tailgater can get around you. Staying right fits that advice. The handbook directly warns not to speed up, since being tailgated at a low speed is safer than at a high speed.
6. If you are being tailgated, you should:
- Drive on the shoulder.
- Pull off the roadway.
- Drive faster.
- Allow the vehicle to pass. ✓
Answer: D. Allow the vehicle to pass.
If you are being tailgated, allow the vehicle to pass by holding a steady, low speed and leaving extra room in front of you so the tailgater can get around. The handbook lists specific responses for a tailgater: avoid quick changes by signaling early and slowing gradually, open up your following distance, and do not speed up. It notes that extra room ahead both reduces your need for sudden moves and makes it easier for the tailgater to get past you. So the goal is not to escape the tailgater but to make passing them easy and predictable. The handbook also warns against tricks like flashing brake lights or turning on taillights.
7. Stopping distance can be affected by:
- Speed. ✓
- Temperature.
- Time of day.
- Traffic.
Answer: A. Speed.
Stopping distance can be affected by speed; as speed increases, the distance needed to stop increases. The handbook's stopping-distance figure shows that braking distance grows sharply with speed: doubling speed makes braking distance four times longer, and tripling it makes it nine times longer. It also says high speeds increase stopping distances, while slowing down reduces braking distance. The total stopping-distance formula is perception distance plus reaction distance plus braking distance, and the air-brake section adds brake lag for those systems. Temperature and time of day do not appear as parts of that formula or as factors in the speed discussion.
8. When driving a combination rig, following distance should be:
- Decreased in poor weather.
- Shorter than when driving a single vehicle.
- About the same as when driving a single vehicle.
- Longer than when driving a single vehicle. ✓
Answer: D. Longer than when driving a single vehicle.
Following distance in a combination rig should be longer than when driving a single vehicle. The handbook says combination vehicles are usually heavier and longer than single commercial vehicles, so they need more skill and more following room. In the combination-vehicle section it tells you to follow far enough behind other vehicles using a time gap based on your vehicle's length, plus an extra second over 40 mph, and to allow lots of following distance so you can brake early. Because a combination rig is longer than a single vehicle, that length-based gap works out to a longer following distance, not a shorter or equal one.
9. When traveling more slowly than 40 mph, maintain at least ____ of following distance per every 10 feet of your vehicle.
- One second ✓
- Two seconds
- Three seconds
- Four seconds
Answer: A. One second
10. How many seconds of following distance per every 10 feet of vehicle should you maintain when traveling more slowly than 40 mph?
- One second ✓
- Two seconds
- Three seconds
- Four seconds
Answer: A. One second
When you are traveling slower than 40 mph, keep one second of following distance for every 10 feet of vehicle length. The handbook states the space-ahead rule directly: at least one second for each 10 feet of vehicle length at speeds below 40 mph, and at higher speeds you add one more second. So a 40-foot vehicle needs 4 seconds under 40 mph, and a 60-foot rig needs 6 seconds, matching the examples given. The passages also explain the reason for the rule: space ahead is what lets you stop if traffic in front of you slows suddenly, and following too closely is the most common cause of rear-end crashes for large vehicles.
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Last checked: 2026-10-17 · Verified from official source
Updated: · Based on the official driver handbook