Mississippi General Knowledge CDL Practice Test

This is a free 20-question practice test for the General Knowledge portion of the Mississippi Commercial Driver's License knowledge exam. Questions are pulled from a pool of 97 drawn from the AAMVA CDL Manual, which is the source document the Mississippi Department of Public Safety Driver Service Bureau uses to write its actual exam.

How it works: Click an answer. The correct choice highlights in green, and you'll see a short explanation. Aim for 85% or better before you sit for the real test in Mississippi.

Question 1 of 20

A tire may need replacement if:

Tread depth is below the minimum (4/32 steer, 2/32 other), there are sidewall cuts, exposed cord, or other damage
It looks dirty
It is over a year old
It is the wrong color

Correct. Below-minimum tread depth, sidewall damage, exposed cords, bulges, or excessive wear are all reasons to replace.

Question 2 of 20

You are driving on a steep downgrade and your brakes have failed. The best escape is to:

Pump the brakes furiously
Use a runaway escape ramp
Try to bail out of the cab
Sound the horn and continue

Correct. If a runaway escape ramp is available, use it. Modern arrester beds use loose gravel or sand to slow the vehicle without injury to the driver.

Question 3 of 20

Cargo securement is the responsibility of:

Only the shipper
Only the consignee
The driver, regardless of who loaded the trailer
The dispatcher

Correct. The driver is ultimately responsible for verifying that cargo is properly secured before driving and remains secure throughout the trip.

Question 4 of 20

Hydroplaning is most likely to occur when:

Driving at low speed in light rain
Tires lose contact with the road and ride on water
Brakes are applied gently
Tires are over-inflated

Correct. Hydroplaning occurs when a film of water comes between the tires and the road, causing the tires to lose contact with the pavement. Higher speeds, worn tires, and standing water increase the risk.

Question 5 of 20

On a 6-tire single vehicle, the maximum allowable air loss rate (engine off, brakes released) is:

1 psi per minute
2 psi per minute
3 psi per minute
4 psi per minute

Correct. For a single vehicle, no more than 2 psi per minute leakage with the engine off and brakes released. Combinations are limited to 3 psi/min.

Question 6 of 20

Which of these is a sign of tire failure?

Heavy thumping or vibration
A loud bang
The vehicle pulling to one side
All of the above

Correct. Vibration, a loud bang from a blowout, and pulling to one side are all classic signs of tire failure.

Question 7 of 20

You are driving a 60-foot tractor-trailer at 55 mph. The minimum following distance you should maintain is:

4 seconds
5 seconds
6 seconds
7 seconds

Correct. Above 40 mph, add one extra second to the per-10-foot rule. A 60-foot vehicle = 6 seconds + 1 = 7 seconds at 55 mph.

Question 8 of 20

What is the minimum tread depth required for the front (steering) tires of a commercial vehicle?

1/32 inch
2/32 inch
4/32 inch
6/32 inch

Correct. Steer-axle tires must have at least 4/32-inch tread depth in every major groove. Other tires require at least 2/32 inch.

Question 9 of 20

You are driving a 40-foot vehicle at 35 mph. The minimum following distance you should maintain is:

2 seconds
3 seconds
4 seconds
7 seconds

Correct. The rule of thumb: 1 second per 10 feet of vehicle length below 40 mph. A 40-foot vehicle therefore needs 4 seconds of following distance.

Question 10 of 20

Which of these is the best way to communicate that you are slowing down?

Tap the brake pedal a few times to flash the brake lights
Use the horn
Put on the parking brake
Wave at drivers behind

Correct. Lightly tapping the brake pedal flashes the brake lights, alerting drivers behind that you are slowing.

Question 11 of 20

A driver convicted of driving a CMV with a BAC of .04 or higher faces:

No penalty
A warning
Disqualification of at least one year for the first offense
License renewal

Correct. A first conviction of driving a CMV with BAC ≥ .04 disqualifies the driver for at least one year (three years if hauling hazmat).

Question 12 of 20

How often must drivers inspect their cargo and securing devices?

Within the first 50 miles, then every 150 miles or every 3 hours of driving (whichever comes first)
Only at the start of the trip
Only at fuel stops
Only when entering a new state

Correct. Federal rule: inspect within the first 50 miles, then every 150 miles or 3 hours of driving, whichever comes first, plus every change of duty status.

Question 13 of 20

Which of the following is the best way to prevent a fire in your vehicle?

Carry extra fuel
Smoke only with the windows open
Inspect the vehicle, watch the gauges, and use safe driving practices
Run the engine hot to burn off carbon

Correct. Most fires are preventable through inspection (electrical, fuel-system, tire) and watching gauges, plus prohibiting smoking near fuel and observing safe loading/refueling rules.

Question 14 of 20

Driver fatigue is most often caused by:

Inadequate sleep, long work hours, and night driving
Hot weather
Heavy traffic
Cold meals

Correct. Sleep deprivation, long hours, and circadian-low night-driving hours are the leading causes of fatigue. Sleep before driving; pull over when drowsy.

Question 15 of 20

You are driving in a work zone. You should:

Drive faster to clear the zone
Slow down, increase following distance, watch for workers
Use the shoulder
Honk repeatedly

Correct. Work-zone fines double or more in most states. Slow down, give the vehicle ahead extra space, watch for workers and equipment, and follow signed speed reductions.

Question 16 of 20

You should test your brakes before going down a hill by:

Driving down to test them
Pumping the pedal at the top
Lightly applying them as you start the descent to confirm they are working
Doing nothing

Correct. Just before the descent, gently apply the brakes at slow speed to confirm response. Combined with selecting a low gear in advance, this is the safe practice.

Question 17 of 20

The blood-alcohol concentration (BAC) at or above which a CDL driver is considered to be driving under the influence in a commercial motor vehicle is:

Correct. The federal BAC limit for CDL drivers operating a commercial vehicle is .04 — half the .08 limit for non-commercial drivers in most states.

Question 18 of 20

What is the only effective way to remove alcohol from the body?

Drinking coffee
Cold showers
Eating a heavy meal
Time

Correct. Only time eliminates alcohol from the body — at roughly one drink per hour. Coffee, food, and showers do not speed up the process.

Question 19 of 20

You are driving on a two-lane road. An oncoming driver drifts into your lane. You should:

Steer right onto the shoulder
Flash your high beams
Honk your horn
Brake hard and stop in your lane

Correct. When an oncoming driver drifts into your lane, the safer escape is right onto the shoulder. Steering left risks a head-on if the other driver corrects.

Question 20 of 20

What is the minimum amount of tread depth required on tires other than front (steering) tires?

1/32 inch
2/32 inch
4/32 inch
5/32 inch

Correct. Non-steer tires must have at least 2/32-inch tread depth in every major groove.

About the Mississippi General Knowledge exam

Most state DMVs administer 50 General Knowledge questions and require 80% (40 correct) to pass. Questions are pulled from a much larger pool, so two applicants taking the test on the same day will see different mixes. The questions on this site are drawn from the AAMVA CDL Manual chapters that every state's exam is built from.

The Mississippi Department of Public Safety Driver Service Bureau follows the federal CDL standards established by FMCSA. To earn the General Knowledge credential, you must answer at least 80% of the questions correctly. Many candidates score lower the first time because the test pulls from a large pool — refreshing this page will give you a different mix of questions, drawn from the same authoritative source.

Want more practice? Try the full General Knowledge question bank or browse all Mississippi CDL practice tests.