The subject list is federal, not your state's
49 CFR 383.111 opens by saying all commercial vehicle operators must have knowledge of twenty
general areas, and then names all twenty. That section is the syllabus. It does not change when you
cross a state line, which is why the same study material works in every state and why we run one
national question bank rather than fifty-one.
The same section adds two more lists. Paragraph (b) sets out seven areas for anyone driving a
vehicle with air brakes. Paragraph (c) sets out three for combination vehicles. Those are separate
exams, so they are not on general knowledge, but the overlap is real: cargo, inspection and braking
show up in more than one place.
The twenty areas, in the rule's own order
49 CFR 383.111(a) lists them as: safe operations regulations, safe vehicle control systems,
commercial vehicle safety control systems, basic control, shifting, backing, visual search,
communication, speed management, space management, night operation, extreme driving conditions,
hazard perceptions, emergency maneuvers, skid control and recovery, the relationship of cargo to
vehicle control, vehicle inspections, hazardous materials, mountain driving, and fatigue and
awareness.
Two of those are worth reading twice. "Safe operations regulations" is the rule pointing at other
rules — parts 391, 392, 393, 395, 396 and 397 — covering inspection and maintenance duties, the
effects of fatigue and poor health, and the effects of alcohol and drug use. And "hazardous
materials" is on the general knowledge test even though hazmat is a separate endorsement. The rule
asks you to know what makes a material hazardous, the classes, the labeling and placarding
requirements, and that the endorsement needs its own training. You are tested on the awareness, not
on the endorsement material.
Which areas carry the most questions
Nothing in 383.111 says how many questions each area gets. Anyone who tells you the exact split is
guessing, so treat all twenty as fair game. What you can measure is how much room the handbook gives
each one, and that is a fair signal of how deep the questions go.
In the Texas CDL handbook, general knowledge is mostly Section 2, "Driving Safely", which runs from
subsection 2.1 to 2.23, plus Section 3, "Transporting Cargo Safely". Inside Section 2, vehicle
inspection (2.1), controlling speed (2.6) and managing space (2.7) each get seven subsections of
their own. Seeing hazards (2.8) gets four. Those four subjects are the spine of the test. Distracted
driving, road rage, fog, winter, hot weather, railroad crossings, mountain driving, emergencies,
antilock brakes, skids, crash procedures, fires and the alcohol and drug rules all get their own
subsections too, and each of them maps onto a named area in 383.111.
Where people actually lose marks
Stopping distance arithmetic. The handbook breaks total stopping distance into three parts:
perception, reaction and braking. It puts average perception time for an alert driver at one and
three-quarter seconds, which is 142 feet at 55 mph, and reaction time at three-quarters of a second
to a second, which is 61 feet. Braking at 55 mph on dry pavement with good brakes takes about 216
feet. The total minimum is 419 feet. People remember the 419 and forget it is made of three pieces,
then miss the question that asks about one piece.
The empty truck. The same section says empty trucks need greater stopping distances, because an
empty vehicle has less traction and the brakes, tires, springs and shock absorbers on a heavy vehicle
are built to work best fully loaded. It reads backwards, so it gets answered backwards.