Speed Limits & Following Distance — California
California CDL practice test: 392 free practice questions (20 official sample questions · Official driver handbook). The official format is not yet verified; check the official site before your test. Speed Limits & Following Distance: 16 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 | California CDL permit (CLP) knowledge tests |
| Topic questions | 16 (4% of 392 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
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Questions (16)
1. Three things add up to the total stopping distance for your vehicle. They are:
- perception distance, reaction distance, braking distance. ✓
- observation distance, reaction distance, slowing distance.
- perception distance, response distance, reaction distance.
Answer: A. perception distance, reaction distance, braking distance.
The three parts are perception distance, reaction distance, and braking distance. The handbook gives the formula as perception distance plus reaction distance plus braking distance equals total stopping distance. Perception is the distance from seeing a hazard until your brain recognizes it. Reaction is the distance you keep moving before you physically hit the brakes. Braking is the distance covered while the brakes are applied. Section 2 uses these three to define total stopping distance. The air-brake section later adds brake lag as an extra delay for air-brake systems, but the basic three-part breakdown is still the one asked here.
2. When in heavy traffic, the safest driving speed is:
- Slower than the speed being driven by surrounding traffic.
- The same speed being driven by surrounding traffic. ✓
- Faster than the speed being driven by surrounding traffic.
Answer: B. The same speed being driven by surrounding traffic.
In heavy traffic, the safest speed is the same speed the surrounding traffic is driving. The handbook says directly that when traffic is heavy you should travel at the speed of other vehicles, because vehicles moving the same direction at the same speed are not likely to run into one another. It adds that you should drive with the flow of traffic if you can do so without going at an illegal or unsafe speed. That is why matching surrounding traffic is the correct choice, not picking a speed above or below the pack.
3. A ramp's posted speed limit:
- Is suitable for all vehicles.
- Is suitable for some vehicles, but may be too fast for a large CMV. ✓
- Is just a suggestion and may be exceeded.
Answer: B. Is suitable for some vehicles, but may be too fast for a large CMV.
A ramp's posted speed limit is suitable for some vehicles, but it may be too fast for a large CMV. The handbook says off ramps and on ramps often have posted speed limit signs, and it warns that those speeds may be safe for automobiles but may not be safe for larger or heavily loaded vehicles. That is why the sign is not a guarantee for your truck. A downhill exit that also turns is especially risky because the downgrade makes it hard to slow down, and braking while turning is dangerous. The safe approach is to be going slowly enough before you reach the curved part of the ramp.
4. While operating on a downgrade, you should brake until you reach a speed that is:
- 5 mph below your safe speed. ✓
- 10 mph below your safe speed.
- 15 mph below your safe speed.
Answer: A. 5 mph below your safe speed.
Brake until you are about 5 mph below your safe speed, then release the brakes. The handbook describes the braking technique for a long or steep downgrade. With the vehicle in the proper low gear, the engine does most of the slowing and the brakes are only a supplement. You apply the brakes enough to cause a clear slowdown, then release them once your speed is roughly five mph under your safe speed. When speed rises back to the safe speed, you repeat the process. That makes five mph below safe speed the release point.
5. If you are braking on dry pavement while traveling at 55 mph, how much distance will brake lag add to your overall stopping distance?
- 32 feet ✓
- 45 feet
- 20 feet
Answer: A. 32 feet
Brake lag adds 32 feet to your overall stopping distance. The handbook explains that with air brakes there is a delay while air flows through the lines before the brakes actually work. At 55 mph on dry pavement, that brake lag distance is about 32 feet. The handbook also lists brake lag as one of the four parts of total stopping distance, along with perception, reaction, and braking distance. So the added distance from brake lag is 32 feet.
6. Trailers with low underneath clearance may be difficult to drive:
- On interstate highways.
- Over railroad crossings. ✓
- On dirt roads.
- At the posted speed limit.
Answer: B. Over railroad crossings.
Trailers with low underneath clearance can be hard to drive over railroad crossings, where the trailer may get hung up on the tracks. The handbook points to railroad crossings as a special problem for trailers that sit low to the ground. It warns that you should not gamble on getting hung up halfway across the tracks. The clearance between the trailer's underside and the road surface is what matters at the raised rails and crossing surface, and that same warning appears both in the driving safely section and in the combination vehicles section, so the risk is tied to crossings rather than to open highway driving.
7. On a slippery surface, stopping distance:
- Is longer than on a regular driving surface. ✓
- Is not as long as on a regular driving surface.
- Is about the same as on a regular driving surface.
Answer: A. Is longer than on a regular driving surface.
On a slippery surface, stopping distance is longer than on a regular driving surface. The handbook says traction is the friction between tires and the road, and slippery conditions reduce it. It states directly that it will take longer to stop when the road is slippery, and wet roads can double stopping distance. That is why you must slow down to stop within the same distance you would need on a dry road. The correct choice simply matches that rule: a slippery surface makes the stop take more distance, not less.
8. After two violations of any state law regarding hand-held mobile phone use:
- You will need to cancel your mobile phone service.
- Your CDL will be disqualified. ✓
- You will be required to drive 10 mph under the posted speed limit for a period of time.
Answer: B. Your CDL will be disqualified.
After two or more convictions for violating a state law on hand-held mobile phone use, your CDL will be disqualified. The handbook states that a CDL is disqualified after two or more convictions of any state law on hand-held mobile telephone use while operating a CMV. It adds that the disqualification lasts 60 days for a second offense within three years, and 120 days for three or more offenses within that period. The same section also bars motor carriers from requiring or letting drivers use hand-held phones, and it notes the first and later violations can bring civil penalties on the driver.
9. The weight of a truck:
- Usually has no impact on stopping distance.
- Is a major factor affecting stopping distance. ✓
- Is not as important as the type of cargo in determining stopping distance.
Answer: B. Is a major factor affecting stopping distance.
The weight of a truck is a major factor affecting stopping distance. The handbook's section on speed and stopping distance includes a discussion of how vehicle weight affects stopping distance. It says the heavier the vehicle, the more work the brakes have to do to stop it, and the more heat they absorb. That means a loaded or heavy truck takes more braking effort than a light one, so weight is a big factor in how long it takes to stop, not a minor detail you can ignore when judging your following distance and speed.
10. If braking at a speed of 55 mph while driving on dry pavement, the brake lag can add ____ to your vehicle's total stopping distance.
- 32 feet ✓
- 15 feet
- 50 feet
Answer: A. 32 feet
At 55 mph on dry pavement, brake lag adds about 32 feet to your total stopping distance. The air brakes section explains that with air brakes there is an added delay called brake lag: the time it takes for air to travel through the lines and make the brakes work after you push the pedal. Unlike hydraulic brakes, which work instantly, air brakes take a half second or more. The handbook states that at 55 mph on dry pavement this lag distance adds about 32 feet, and it lists brake lag as one of the four parts of total stopping distance.
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Last checked: 2026-10-17 · Not yet verified
Updated: · 20 official sample questions · Official driver handbook