Read the rule behind the answer.

Section 1

General Knowledge

A commercial driver's license is required to operate a commercial motor vehicle. The class you need depends on the weight you drive and tow, and on what you are carrying.

• Class A: a combination with a gross combination weight rating of 26,001 pounds or more, where the towed unit is over 10,000 pounds
• Class B: a single vehicle of 26,001 pounds or more, which may tow a unit of 10,000 pounds or less
• Class C: vehicles that do not meet Class A or B but carry hazardous materials requiring placards, or are designed to transport 16 or more people including the driver

Endorsements are added to a CDL for specific work: hazardous materials, tank vehicles, passenger transport, school bus, and doubles/triples. A hazardous materials endorsement additionally requires a federal security threat assessment.

Serious traffic violations and any alcohol or drug offense can disqualify a commercial driver, and the thresholds are stricter than for a regular license. Disqualification can follow from conduct in your personal vehicle as well as a commercial one.

Source: FMCSA / 49 CFR, as adopted in the AAMVA model CDL manual.

Section 2

Safe Driving

Stopping includes travel while recognizing the hazard, reacting, and braking. Air-brake systems add travel during the delay between pedal application and brake action.

• Perception distance — how far you travel while recognizing a hazard
• Reaction distance — how far you travel before your foot reaches the brake
• Brake-lag distance — additional travel while an air-brake system responds after pedal application
• Effective braking distance — how far you travel once the brakes are actually applied

Because braking distance grows faster than speed, doubling your speed more than doubles the distance needed to stop. A loaded vehicle also handles differently from an empty one: empty trucks can take longer to stop, since the brakes and tires are designed for a loaded weight.

Adjust following distance for length and conditions. A common rule is one second of following distance for every 10 feet of vehicle length below 40 mph, adding a second above that, and adding more for rain, snow, fog, or darkness.

Technical source: Oregon DMV Commercial Driver Manual, sections 2.6.1, 2.7.1 and 5.4.4. Use the current state manual and vehicle instructions. Source-assisted review is not instructor approval.

Section 3

Emergency

In most emergencies, stopping is not the fastest way out of trouble. Steering around a hazard usually takes less distance than braking to a stop at highway speed, so leaving the road onto a shoulder or open area is often safer than a head-on collision.

• Brake failure on a downgrade: look for an escape ramp, then an open uphill or level area to slow the vehicle
• Tire blowout: hold the steering wheel firmly, stay off the brake until the vehicle slows, then ease off the road
• Skid from over-braking: release the brake, and if the drive wheels have lost traction, steer where you want to go and countersteer as the vehicle straightens
• Antilock brakes: press and hold firm pressure; do not pump the pedal

Drowsy driving is a leading factor in commercial crashes. Coffee, cold air, and loud music mask fatigue rather than fixing it — the only real remedy is to stop somewhere safe and rest.

Source: FMCSA / 49 CFR, as adopted in the AAMVA model CDL manual.

Section 4

Hours of Service

Hours-of-service rules limit how long you may drive so that fatigue does not accumulate across a shift or a week. The limits below are the federal rules for property-carrying drivers; passenger-carrying limits differ.

• 11-hour driving limit after 10 consecutive hours off duty
• The usual 14-hour driving window starts when duty begins; a qualifying split-sleeper pairing is an exception.
• After 8 cumulative driving hours without a 30-minute interruption, take 30 consecutive minutes without driving. On-duty non-driving time, off-duty time, sleeper-berth time, or consecutive combinations can qualify.
• No driving after 60 on-duty hours in 7 days, or 70 in 8 days for carriers operating every day. A restart uses at least 34 consecutive off-duty hours.

Records of duty status are kept electronically for most drivers. Falsifying them is a serious violation, and the rules exist because the fatigue they manage is not something a driver can reliably self-assess.

Source: FMCSA / 49 CFR, as adopted in the AAMVA model CDL manual.

Section 5

Vehicle Inspection

Federal rules require inspection before, during, and after a trip. Inspection is not paperwork — most catastrophic failures announce themselves first as something visible or audible on a walkaround.

• Pre-trip: a full inspection before the vehicle moves
• En route: check tires, brakes, cargo securement, and lights at each stop
• Post-trip: complete a driver vehicle inspection report noting any defect that would affect safety

A defect that affects safe operation must be repaired before the vehicle is driven again. Schedule pressure is never a valid reason to move a vehicle with a critical defect such as a cracked air line, an inoperative brake, or a flat tire.

Source: FMCSA / 49 CFR, as adopted in the AAMVA model CDL manual.

Section 6

Pre-Trip Inspection

The FMCSA model manual describes a pre-trip inspection in which the candidate identifies safety-related parts and explains what they would inspect to help confirm a safe operating condition. Follow your state's CDL manual and test instructions.

• Engine compartment: fluid levels, belts, hoses, wiring, leaks
• Cab: gauges, warning lights and buzzer, steering play, horn, wipers, mirrors, emergency equipment
• Lights and reflectors: clean, working, correct color, properly mounted
• Tires: tread depth, inflation, no cuts or bulges; wheels and rims free of cracks, all lug nuts present
• Brakes: linings, drums, hoses, slack adjusters, and an air brake check
• Coupling and cargo: fifth wheel, locking jaws, safety devices, and securement of the load

Emergency equipment must be present and usable: spare electrical fuses where required, three warning devices such as reflective triangles, and a properly charged and rated fire extinguisher.

Source: FMCSA / 49 CFR, as adopted in the AAMVA model CDL manual.

Section 7

Air Brakes

Air brakes use compressed air to apply force at each wheel. They are effective, but they fail in specific ways that a driver is expected to recognize before the vehicle is in motion.

• The governor controls when the compressor loads and unloads air, commonly cutting out near 125 psi and cutting back in near 100 psi
• Check the low-air warning against the applicable manual and vehicle specification; do not assume one threshold applies to every vehicle
• Spring brakes apply automatically as system pressure falls, typically between 20 and 45 psi
• Drain moisture from air tanks daily; water collects and can freeze in cold weather

Brake fade on a long downgrade comes from overheated drums, not from a lack of pedal force. Pressing harder makes it worse. Select a low gear before starting down, so the engine does most of the work of holding speed.

Because air brakes have a lag before they take effect, total stopping distance is longer than for a hydraulic system at the same speed.

Source: FMCSA / 49 CFR, as adopted in the AAMVA model CDL manual.

Section 8

Combination Vehicles

A combination vehicle behaves differently from a straight truck because the trailer follows its own path and reacts to steering with a delay.

• Off-tracking: the rear wheels follow a tighter path than the front, so turns must be started later and wider to keep the trailer off the curb
• Rearward amplification: a quick steering movement is magnified toward the back of a long combination, so the rear can swing much farther and faster than the cab
• Trailer skids: if the trailer begins to swing out, release the brake to regain traction and steer to bring it back in line
• Empty trailers skid more easily than loaded ones, because the brakes and suspension are built for weight that is not there

For conventional tractor-semitrailer coupling, prepare and align the fifth wheel, verify trailer height, and follow the equipment procedure for air and brake checks before engagement. A gentle tug with trailer brakes locked and a secured visual inspection are both needed. Check plate contact, jaws around the kingpin shank, and the lock. Before uncoupling, secure the trailer, lower its landing gear, disconnect and stow lines, and unlock as prescribed. Stop partly clear with the tractor frame under the trailer; secure the tractor and inspect support before pulling fully clear.

Source-assisted review of coupling paragraph: Oregon DMV Commercial Driver Manual, sections 6.4.1–6.4.2, accessed 2026-09-07. Vehicle-specific procedures differ. Independent instructor review is pending.

Section 9

Weight Distribution

Legal weight is not one number. A vehicle can be under its gross limit and still be illegal or unsafe because weight sits in the wrong place.

• Gross vehicle weight rating: the maximum for a single vehicle as specified by the manufacturer
• Gross combination weight rating: the maximum for the power unit plus the towed unit
• Axle weight: how much of the load each axle carries, which is limited separately from the total
• Federal bridge rules further limit weight based on axle spacing, not just axle count

Weight carried high raises the center of gravity and makes rollover more likely in a curve or an evasive maneuver. Load heavy items low and distribute them evenly; a load braced only at the back can shift forward under braking.

Source: FMCSA / 49 CFR, as adopted in the AAMVA model CDL manual.

Section 10

Hazardous Materials

Hazardous materials transport is governed by rules covering what is carried, how it is identified, and who may carry it. A hazardous materials endorsement requires a knowledge test and a federal security threat assessment.

• Required shipping papers: at the controls, keep them within reach while belted and visible to someone entering, or in the driver-side door holder. Away from the controls, use that holder or the driver’s seat.
• Placards warn others what is on board and must match the material and quantity carried
• The driver is responsible for refusing leaking or improperly packaged shipments
• Some materials may not be loaded together; segregation rules apply

Attend the vehicle as required, park away from open fires and bridges where restricted, and follow route restrictions — some tunnels and populated areas prohibit certain classes entirely.

For a spill or leak, keep clear and upwind, warn others away, and call for help. Do not identify material by smell or touch. Do not attempt leak repair without suitable training and equipment. Move a leaking vehicle only as safety requires and only without endangering people, spreading contamination, or damaging the vehicle. If hazardous cargo is burning, keep clear and do not open cargo doors. Routine attendance distances are not emergency isolation distances.

Emergency and paper-location review: Oregon DMV CDL Manual 9.7.1–9.7.4, https://www.oregon.gov/odot/dmv/pages/online_cdl_manual_2/section_9.aspx; 49 CFR 177.817(e) and 397.5. Accessed 2026-09-07. Source-assisted review of these topics only; other claims in this section and independent approval remain pending.

After unloading a placarded cargo tank, keep required placards while hazardous residue remains unless a specific exception applies. Sufficient cleaning and vapor purging to remove the potential hazard is one exception, not the only one. Separately, an FMCSA safety permit depends on the material and the quantity or packaging limits in 49 CFR 385.403. A covered vehicle carries a permit copy or a document clearly identifying its FMCSA Safety Permit number. Sources: 49 CFR 172.514(b), 385.403, and 385.415(a)(1). Accessed 2026-09-07; independent review pending.

RQ on a shipping paper identifies a reportable quantity of a hazardous substance; it does not mean a release has happened. For an incident covered by 49 CFR 171.15(b), the person in physical possession gives NRC telephone notice as soon as practical, no later than 12 hours. A separate EPA rule can require immediate notice upon knowledge of a covered hazardous-substance release. The 24-hour RQ measurement period is not a waiting period. Sources: 49 CFR 172.203(c)(2), 171.15 and its EPA note; EPA Reportable release time period. Accessed 2026-09-07; independent review pending.

Section 11

Tank Vehicles

Liquid in a partly filled tank can move as speed changes. This surge can affect control, even after the vehicle stops. Allow extra following space and brake early and smoothly.

• Baffles with openings reduce forward-and-back surge. Side-to-side movement can still contribute to rollover.
• Bulkheads divide the tank into compartments. Load them with proper front-to-rear weight distribution.
• Leave the product-specific outage, or expansion space. Do not fill a liquid tank completely to try to stop surge.
• Before loading, unloading, or driving, follow the tank operator manual: check leaks, closures, working vents, and fitted emergency shut-off equipment.

Reduce speed before curves and ramps. Posted speeds may be too fast for a loaded tanker. Use smooth steering and speed changes on straight roads too. A particular fill level does not guarantee a safe stopping distance or freedom from rollover.

Sources: Oregon DMV Commercial Driver Manual, section 8.1–8.3, https://www.oregon.gov/odot/dmv/pages/online_cdl_manual_2/section_8.aspx; FMCSA Cargo Tank Truck Rollover Prevention, https://www.fmcsa.dot.gov/rolloverprevention. Accessed 2026-09-07. Source-assisted review; independent approval pending.

Section 12

Passenger Transport

Carrying passengers adds responsibilities that begin before the vehicle moves and continue after it stops.

• Inspect passenger items before driving: seats secure, emergency exits operable, handholds and floors in safe condition
• Passengers may not stand forward of the standee line, and baggage must not block an exit or the aisle
• Announce and secure the vehicle at stops; use the parking brake whenever the driver's seat is left
• Do not fuel with passengers aboard unless there is no safe alternative, and never fuel in an enclosed space with passengers on board

The federal crossing-stop rule lists buses transporting passengers and includes specific exceptions. When a stop is required, stop 15–50 feet from the tracks, look and listen, and cross only when clear without shifting gears. State and local rules can impose additional duties. Do not infer the rules for an empty school bus from the federal passenger-bus category alone.

Source for crossing paragraph: 49 CFR 392.10(a)(1) and (b), accessed 2026-09-07. Other passenger procedures in this section still need full review.

Section 13

Doubles and Triples

Doubles and triples add articulation points, inspection work, and handling risks. A quick steering change can be amplified toward the rear, so plan room for smooth speed and direction changes.

• Rearward amplification can magnify a rapid steering input toward the rear; avoid abrupt maneuvers and reduce speed before curves
• Put the most heavily loaded trailer directly behind the tractor and the lightest at the rear
• Check the converter dolly: air lines connected, pintle hook latched, safety chains secured, landing gear fully raised
• Inspect the air and electrical lines for damage and make sure they will not catch or drag
• Allow extra space for the whole combination and make turns and lane changes gradually

Follow the procedure for the specific combination. For conventional doubles, secure and support the rear semitrailer before releasing its fifth wheel. Keep the dolly attached to the front trailer while withdrawing it slowly. Do not unlock the pintle hook while the dolly remains under the rear trailer; the tow bar can fly upward.

Source-assisted review: Oregon DMV Commercial Driver Manual, sections 7.1–7.4, accessed 2026-09-07. Independent instructor review is pending.

Section 14

School Bus

Nearly every school bus rule exists because a child near the bus is often exactly where the driver cannot see. The danger zone is the area around the bus where students are at the greatest risk of being struck, either by passing traffic or by the bus itself.

• The danger zone reaches as far as 30 feet in front of the bumper, and the first 10 feet are the most dangerous
• It extends about 10 feet from each side and 10 feet behind the rear bumper
• Crossover mirrors show the front bumper area, the service door and the front wheel area that direct vision misses
• Students should wait at least 10 feet from the bus, where the driver can see them
• Never let a student retrieve a dropped item without your signal — bending down puts them out of sight
• Count students off and account for every one before moving, then walk the aisle after every route

A bus stalled on or adjacent to a rail crossing requires evacuation; an ordinary controlled stop before the crossing is not the same situation. Fire or threat of fire, impending collision, and an unstable position also require prompt action. Use the emergency plan, select a safe place away from the hazard, and account for every student. Some spills or other conditions can make evacuation into the hazard more dangerous; assess the specific emergency.

Know the state, local, and school-system railroad-crossing procedure, including empty-bus duties. The general procedure uses a 15–50-foot stop when required, quiet conditions for looking and listening, enough room for the whole bus to clear, and no gear change on the tracks. One federal passenger-bus rule does not establish every school-bus duty.

Sources for emergency/crossing paragraphs: Oregon DMV Commercial Driver Manual 10.3–10.4 and 49 CFR 392.10, accessed 2026-09-07. School-bus rules vary by state. Independent review of the complete section remains pending.

Section 15

Longer Combination Vehicles

A longer combination vehicle is a tractor pulling two or more trailers at a gross weight above 80,000 pounds. It is not a CDL endorsement: operating one requires a distinct training program under 49 CFR 380, on top of the doubles/triples endorsement on your license.

• Routes have been frozen since the 1991 ISTEA freeze — no state may add routes or raise LCV weights, and most of the country permits none at all
• LCV Doubles and LCV Triples are separate courses; completing one does not qualify you for the other
• Load the heaviest trailer nearest the tractor and the lightest at the rear
• Rearward amplification compounds along the set, so the last trailer swings hardest and loses grip first
• Stopping distance, merge gaps and turning width all grow with the length of the set
• Confirm the permit and configuration before entering a permitted turnpike, not at the gate

Check whether your state permits LCVs before paying for training. Route authority is the entire basis of LCV legality, and in a state outside the freeze the certificate cannot be used at all.

Section 16

Roadside Inspections

A roadside inspection is conducted by authorized personnel on a vehicle already in operation, and the results are recorded on a Driver Vehicle Examination Report.

• Deliver a copy of the report to your carrier when you reach the next terminal; if that is more than 24 hours away, transmit it immediately
• The carrier certifies every noted violation as corrected within 15 days and keeps the form for 12 months
• A vehicle marked out of service may not be operated — including towed, except by crane or hoist — until all required repairs are done
• Nobody removes the out-of-service sticker before the repairs named in the notice are complete
• A vehicle found unsafe on the road may continue only to the nearest place repairs can safely be made

Roadside findings attach to your driver record as well as the carrier's safety score. The pre-trip you perform before the scale is the part of the outcome you control.

Section 17

Vehicle Maintenance and Repair

Carriers must systematically inspect, repair and maintain every vehicle under their control, and the driver's daily report is the entry point to that system.

• Prepare a driver vehicle inspection report at the end of each day's work; none is required if you found no defect and none was reported to you
• The report covers at least service and parking brakes, steering, lights and reflectors, tires, horn, wipers, mirrors, coupling devices, wheels and rims, and emergency equipment
• Carriers keep the report and its repair certification for three months; maintenance records are kept one year, and six months after the vehicle leaves their control
• Before driving, satisfy yourself the vehicle is safe, review the last report where one is required, and sign for the certified repairs
• Every commercial vehicle must have passed a periodic inspection within the preceding 12 months, with documentation carried on the vehicle
• In a combination, each unit is inspected separately — tractor, semitrailer, full trailer and converter dolly

Annual inspections must be done by a qualified inspector. Passing the CDL air brake knowledge and skills tests counts as qualifying evidence for assigned brake inspection tasks.

Section 18

Trip Planning

Planning a run means fitting the route, the hours and the load checks together before you start, because none of the three can be renegotiated once you are moving.

• For property-carrying drivers, the usual limits are 11 driving hours after 10 consecutive hours off duty and a 14-hour driving window; qualifying exceptions, including split-sleeper pairings, have separate rules.
• A consecutive 30-minute interruption of driving is required before more than 8 hours of driving time have passed
• The cycle limits count on-duty time: 60 hours in 7 days, or 70 in 8 days for carriers operating every day. A restart requires at least 34 consecutive hours off duty.
• Inspect the cargo and its securement within the first 50 miles, then at each change of duty status, after 3 hours, or after 150 miles, whichever comes first
• A vehicle carrying hazardous materials is driven and parked under the laws of the jurisdiction it is in, unless a federal rule is stricter
• Bad weather is part of the plan: reduce speed in snow, ice, fog, rain, dust or smoke, and stop when conditions become dangerous

Plan fuel, scales, parking and rest around the clock you actually have, not the clock the schedule assumes. Running out of hours at a place with nowhere legal to park is a planning failure, not bad luck.

Section 19

Communications on the Job

Most communication on a run is with people who are not in the cab: the carrier, enforcement, emergency services, and every driver approaching your stopped vehicle.

• Hand-held mobile phone use while driving is prohibited; the only exception is reaching law enforcement or emergency services
• Driving includes being temporarily stationary in traffic or at a control device — the restriction lifts only once you pull off to a safe stopping place
• Turn on the hazard flashers immediately when you stop on the road or shoulder, and place the warning devices within 10 minutes
• On a two-lane road: one device about 10 feet toward approaching traffic, one at 100 feet toward that traffic, one at 100 feet the other way
• Within 500 feet of a hill, curve or other view obstruction, move one device 100 to 500 feet toward it
• On a divided or one-way road, place devices within 10 feet, at 100 feet, and at 200 feet toward approaching traffic
• Report a logging device malfunction to the carrier in writing within 24 hours and keep paper records until it is fixed

Carriers hauling Division 1.1, 1.2 or 1.3 explosives must give the driver written instructions naming who to contact and what to do in a fire, crash or leak. Carry them and know them before you need them.

Section 20

Driver Rights, Coercion and Whistleblower Protection

Federal rules protect a driver who refuses to break them. Knowing the two complaint routes is the difference between a refusal that costs you a job and one that is on the record.

• Coercion is a threat to withhold work or take adverse action to make you operate after you said the conditions would put you in violation
• The prohibition binds motor carriers, shippers, receivers and transportation intermediaries, and their agents and officers
• File a written coercion complaint no later than 90 days after the event, naming the person, the provisions involved and the facts
• A harassment complaint about logging technology follows the same 90-day deadline
• A carrier may not coerce you into falsely certifying your data entries or your record of duty status
• If you are fired or disciplined for refusing to operate in violation or in real danger, file with the Secretary of Labor within 180 days

The whistleblower protection covers a refusal to operate when operating would break a safety regulation, or when a reasonable driver in your position would see a real danger of injury.

Section 21

Environmental Compliance

A commercial vehicle can damage the environment in two ways: what it releases in an incident, and what it emits every day it runs.

• Telephone the National Response Center as soon as practical and no later than 12 hours after a reportable hazardous materials incident
• File the detailed written incident report within 30 days of discovery, and keep a copy for two years
• The written report covers any unintentional release or hazardous waste discharge, even where no telephone report was required
• A marine pollutant release above 119 gallons of liquid or 882 pounds of solid requires immediate telephone notice
• A placarded vehicle stopped on a public road is attended by its driver, on the vehicle or within 100 feet with it in clear view
• No part of the exhaust system may leak or discharge forward of or directly below the driver or sleeper compartment
• Exhaust outlets may not discharge below the fuel tank or filler pipe, and exhaust may never be repaired with wrap or patches

Idling limits, emissions testing and spill reporting thresholds are also set by states and localities, and they vary. Check the rules for the jurisdictions on your route — federal rules are the floor, not the ceiling.

Section 22

Basic Vehicle Control

Controlling a combination vehicle is mostly about knowing where the parts you cannot see are going: the trailer, the rear wheels, and the top of the load.

• Judge lane position from fixed reference points in both mirrors, checking often rather than correcting after a wheel has drifted
• Use the whole acceleration lane to reach traffic speed before merging; slow down for an exit in the deceleration lane, not the through lane
• Reach the intersection before swinging wide on a right turn — swinging early invites a car up your right side
• Do not cut a left turn short: the trailer tracks inside your line and sweeps the corner
• Walk a tight yard and plan a way out before driving into it, and check posted clearance against today's load height
• If a maneuver stops looking safe, stop and reset — a pull-up costs a minute, a trailer corner costs a lot more

This is theory. The turns, the lane position and the restricted-area work are graded behind the wheel, and reading about them is not the same as having done them.

Section 23

Shifting and Transmissions

Gear selection decides how much control and how much fuel a trip uses, and on a grade it decides whether the brakes are enough.

• Double-clutching: clutch to neutral, release, then clutch again to select the gear, matching engine and road speed in between
• Shift points come from engine speed and road speed together, not from throttle position or elapsed time
• Progressive shifting — upshifting before the engine reaches full speed — lowers revolutions and fuel use
• A dual-range transmission uses the same pattern twice; the range is changed at the top of the low set
• Do not shift part-way through a curve or an intersection: the gear change unsettles traction where it matters most
• Select the gear for a grade before starting down it — once rolling, no lower gear will match the road speed
• If the transmission will not go back into gear, stop safely; never coast in neutral or force the lever

This is theory. Executing shifts smoothly is range and road work, and no amount of reading substitutes for it.

Section 24

Backing and Docking

Backing is the maneuver with the least visibility and the most damage per mistake, which is why the procedure is a procedure and not a knack.

• Get Out And Look before you start, and again whenever you lose track of what is behind you
• Prefer sight-side backing: the driver's side keeps the trailer and its path in direct view
• Agree hand signals with a spotter before starting, including one signal that means stop now
• Evaluate the dock first — surface, slope, obstructions and overhead clearance
• Correct drift with small, early steering inputs; a trailer amplifies everything the steering axle does
• Pull up and reset whenever the angle goes wrong; that is normal procedure, not failure
• Back slowly enough to stop instantly, scanning both mirrors alternately the whole way
• Secure the vehicle so it cannot move before anyone loads or unloads at the dock

This is theory. Backing and docking are graded behind the wheel, and the setups only become reliable with practice in a real yard.

Section 25

Vehicle Systems and Malfunctions

Knowing what each major system does is what turns an inspection from a checklist into a diagnosis: engine and cooling, exhaust, brakes, drive train, coupling and suspension.

• Steering: play beyond the allowed limit means wear between the wheel and the road wheels, so your input arrives late
• Suspension: a cracked or broken spring, hanger, U-bolt or torque rod lets the axle move under load
• Coupling: check fifth wheel mounting, the locking jaws around the kingpin, and that no gap shows between the plates
• Drive train: a worn universal joint can drop the shaft on the road at speed
• Cooling: a rising temperature gauge on a grade is the warning that comes before the failure
• Air brakes: pressure should hold with the engine off and brakes released — a falling gauge is a leak
• Air brakes: excess push rod travel at the slack adjuster means the brake is out of adjustment and doing less than you think
• Air brakes: a compressor that never cuts out points at the governor or the system it feeds

A defect you can name is a defect you can report. Write it on the inspection report in the words the mechanic needs, not as "something feels wrong".

Section 26

Fatigue and Wellness

Fatigue is the impairment a driver is least able to judge in themselves, which is why the rule sets a limit and the driver still has to stop before it.

• You may not begin or continue driving while fatigue or illness impairs your alertness, and no carrier may require it
• Only sleep reverses fatigue; coffee, cold air and loud music postpone the feeling without restoring alertness
• Drifting in the lane, missing exits and heavy eyelids mean micro-sleeps have already started
• Alertness dips in the small hours and again in mid-afternoon — plan rest around those windows
• Untreated sleep apnea breaks up sleep, so ten hours in the berth can still leave you impaired
• Treat the 10-hour off-duty period as a real sleep opportunity and the 30-minute break as a real break
• Hours-of-service limits are a ceiling, not a target: stop when fatigue arrives, even with hours left

Wellness is the other half — regular meals, movement, and treating a diagnosed condition. The medical certificate checks whether you are fit; staying fit is the daily part of it.

Section 27

After a Crash

The minutes after a crash decide whether it stays one crash. The order is: yourself, the scene, then the calls.

• Assess your own physical condition first; if you are hurt, assign the calls to someone else at the scene
• Turn on the hazard flashers immediately, then place the warning devices
• Move driveable vehicles out of the traffic lanes after a minor crash; leave a scene with injuries for the responders
• Get emergency medical help, and do not move seriously injured people unless fire makes it necessary
• Use the fire extinguisher on the base of the fire, from as far back as it will reach
• A fatality requires post-crash alcohol and drug testing regardless of any citation
• An injury needing treatment away from the scene, or a tow-away, requires testing only if the driver is cited
• Alcohol testing stops at 8 hours and drug testing at 32 hours, with a written record if the test was missed
• Stay reachable for testing — leaving except for necessary medical care can be treated as a refusal

The carrier keeps an accident register for three years: date, place, driver, injuries, fatalities and any hazardous material released.

Section 28

Drug and Alcohol Rules

The federal testing rules apply to safety-sensitive work, which is more than driving — it includes inspecting, loading, fuelling and waiting to be dispatched.

• No safety-sensitive work at an alcohol concentration of 0.04 or greater
• No alcohol use while performing safety-sensitive functions, and none within four hours before them
• After a crash requiring a test, no alcohol for eight hours or until the test is done
• Schedule I substances are prohibited outright; other scheduled drugs need a prescriber who knows your history and says it will not affect safe driving
• A verified negative pre-employment controlled substances test is required before you first drive for an employer
• Random testing is unannounced; the regulation's minimum annual rates are 10 percent for alcohol and 50 percent for controlled substances
• A violation removes you from safety-sensitive duties until the return-to-duty process is complete
• You must notify current employers in writing of a violation before performing safety-sensitive work again

A test refusal counts as a violation. So does staying unreachable when a post-crash test is required.

Section 29

Medical Qualification

Medical certification is not paperwork about your health; it is the condition on which the license works at all.

• Interstate driving requires you to be at least 21 and able to read and speak English well enough for signs, officials, reports and records
• You may hold a commercial license from one state or jurisdiction only
• Vision: at least 20/40 in each eye and binocularly, with or without correction, and a field of at least 70 degrees in each eye
• You must be able to recognize standard red, green and amber
• Hearing: perceive a forced whisper in the better ear at five feet, or no more than 40 decibels average loss on an audiometric test
• The examination must be performed by a medical examiner on the National Registry
• Most drivers are examined at least every 24 months; insulin-treated diabetes or a vision exemption shortens that to 12 months
• Any illness or injury that impairs your normal duties requires a new examination, whatever time the certificate has left

Conditions such as epilepsy, uncontrolled high blood pressure or a current clinical diagnosis of alcoholism are handled under the physical qualification standard — by the examiner, against 49 CFR 391 subpart E, not by guesswork.