DC CDL General Knowledge cheat sheet

Pre-trip inspection in three passes: walk-around for leaks, damage, and clearance; engine compartment check of fluids, belts, and wiring; then in-cab check of gauges, controls, and warning lamps.

Air brake leak test: with engine off and full pressure, release parking brake and hold service brake; the loss must not exceed 3 psi in one minute for a single vehicle (5 psi per minute for a combination).

Low air pressure warning must activate before pressure drops below 60 psi; the parking brake must automatically engage between 20 and 45 psi on vehicles with spring brakes.

The air compressor should build pressure from 85 to 100 psi within 45 seconds at a fast idle on a typical tractor-trailer; slower buildup indicates a leak or worn compressor.

The 15-point walk-around covers coupling devices, mounting bolts, brake components, exhaust, frame, fuel tank, lights, mirrors, tires, wheels and rims, mud flaps, cargo, and doors.

Tire tread depth minimum is 4/32 inch on steering tires and 2/32 inch on all other tires; sidewall cuts or bulges require the tire to be removed from service.

Pushrod stroke on a slack adjuster that moves more than about 1 inch on a standard chamber indicates brakes out of adjustment and the vehicle is out of service until fixed.

Steering wheel play must not exceed 10 degrees on a power steering system or 10 degrees on a manual system before the vehicle is placed out of service.

Double-clutch procedure: press clutch, shift to neutral, release clutch, press clutch again, shift to the next gear; the intermediate release matches engine and transmission speeds.

Upshift at governed engine speed or the point of maximum torque; downshift before the engine lugs, typically below about 1,000-1,200 rpm depending on the engine.

Backing rule: get out and look (GOAL) before reversing, back on the driver's side whenever possible, and use a spotter who stays visible in the mirror.

If a spotter disappears from view while backing, stop immediately until the spotter is visible again.

Right turns require a wide swing to the left first, then a tight turn to keep the rear wheels from running over the curb; watch the trailer's off-tracking path.

Rear wheels of a tractor-trailer cut the corner; the longer the wheelbase, the more the rear of the vehicle tracks inside the front wheels' path.

Turn signals must be used continuously for at least the last 100 feet before a turn, and lane changes require a signal and mirror check before moving.

When backing a tractor-trailer, turn the steering wheel in the direction you want the trailer to go, then follow with the tractor to avoid jackknifing.

Following distance: at least 1 second per 10 feet of vehicle length at speeds under 40 mph, plus 1 extra second; above 40 mph add 1 second per 10 feet of length.

A 60-foot combination at 55 mph needs at least 7 seconds of following distance; a 50-foot vehicle at 50 mph needs 6 seconds.

Look 12-15 seconds ahead of the vehicle in city traffic and about a quarter mile ahead on the highway to identify hazards early.

Aim high in steering and keep the vehicle centered in the lane; use the lane lines in the mirrors to confirm position.

The most common hazard categories are other drivers, pedestrians, cyclists, weather, road conditions, and cargo shifts; scan for all of them continuously.

If a hazard develops, the first response is to slow down or stop, not to swerve; swerving risks rollover and loss of control.

Use mirrors every 5-8 seconds and before any lane change, turn, or stop to maintain situational awareness.

Space cushion rule: maintain at least one car length of space per 10 mph on each side; if a vehicle tailgates, increase the space ahead rather than braking abruptly.

Total stopping distance equals perception distance plus reaction distance plus braking distance; reaction distance at 55 mph is about 60 feet per second of reaction time.

Perception time is about 3/4 second and reaction time is about 3/4 second; at 55 mph the vehicle travels about 60 feet per second, so 1.5 seconds of perception and reaction covers about 90 feet.

Braking distance increases with the square of speed: doubling speed from 30 to 60 mph roughly quadruples braking distance.

The posted speed limit is a maximum for ideal conditions; reduce speed by at least one-third on wet roads and by half or more on snow or ice.

On a downgrade, use a lower gear and engine braking before the descent; brakes should be applied in short, firm applications to avoid overheating.

The speed limit for a school bus is 55 mph on most highways, and many states set lower limits for trucks and buses on specific routes; obey posted signs.

On a curve, slow to the posted advisory speed before entering; braking in the curve reduces traction available for steering.

Following too closely is the leading cause of rear-end collisions; the space needed grows with speed, weight, and road surface.

Skid recovery: stop braking, steer in the direction of the skid, and do not accelerate until the vehicle is under control again.

A front-wheel skid means the vehicle is not responding to steering; release the brake and let the front wheels regain traction before steering.

A rear-wheel skid means the back of the vehicle is sliding out; steer into the skid to straighten the vehicle.

Brake fade from overheating is prevented by using engine braking on long downgrades and by not riding the brakes.

If a tire blows out, hold the steering wheel firmly, keep the vehicle straight, and slow gradually without hard braking; then move off the road.

If the brakes fail, downshift to a lower gear, use the parking brake gradually, and look for an escape ramp or uphill grade.

Rollover risk: keep the center of gravity low, avoid sharp turns at speed, and do not swerve for small animals or debris.

Fire response: stop, shut off the engine, get all occupants out and away, and call emergency services; do not open the hood fully if the fire is in the engine compartment.

Pass only when the lane ahead is clear, the passing lane is open, and you can see far enough ahead to complete the pass safely; never pass on a hill or curve with limited sight distance.

When being passed, maintain speed and lane position, and move slightly to the right if the passing vehicle needs room.

A commercial vehicle must yield to pedestrians in crosswalks, cyclists, and emergency vehicles with lights and sirens.

Distracted driving includes texting, eating, adjusting the radio, and using a phone; even hands-free calls increase crash risk.

At railroad crossings, stop 15-50 feet from the nearest rail when required, and never stop on the tracks.

School buses with flashing red lights and an extended stop arm require traffic in both directions to stop, except on divided highways where oncoming traffic may proceed.

Cyclists have the same rights as motor vehicles; give at least 3 feet of clearance when passing in many states.

Blind spots on a tractor-trailer are large on both sides and directly behind; use mirrors and turn your head before changing lanes.

The legal limit for commercial drivers is a blood alcohol concentration of 0.04 percent, lower than the 0.08 percent limit for non-commercial drivers.

A CDL holder who refuses a blood alcohol test is disqualified for at least one year, and longer if carrying hazardous materials.

Fatigue impairs reaction time and judgment similarly to alcohol; the only real cure is sleep, not coffee or fresh air.

Hours-of-service rules limit driving to 11 hours after 10 consecutive hours off duty, and require a 30-minute break after 8 hours of driving.

The 60/70-hour rule limits on-duty time to 60 hours in 7 consecutive days or 70 hours in 8 consecutive days for carriers operating every day.

Warning signs of fatigue include yawning, heavy eyes, drifting in the lane, and missing signs or exits; pull over and rest before continuing.

Prescription and over-the-counter medications can impair driving; check labels for drowsiness warnings and consult a doctor before driving.

Alcohol is metabolized at about one drink per hour; coffee, cold showers, and food do not speed up the process.

Federal weight limits: 20,000 pounds on a single axle, 34,000 pounds on a tandem axle group, and 80,000 pounds gross vehicle weight on the Interstate System.

The bridge formula limits the weight on any group of axles based on the number of axles and the distance between the first and last axle.

Cargo must be secured with tiedowns whose working load limit is at least half the weight of the cargo, and the aggregate WLL must be at least half the cargo weight.

At least one tiedown is required for cargo up to 5 feet long and 1,100 pounds; two tiedowns for cargo 5-10 feet long or over 1,100 pounds; three for cargo over 10 feet.

Tiedowns must be attached to the vehicle's frame or rated anchor points, not to the sides of the trailer or to the cargo itself.

Cargo must be checked within the first 50 miles of driving and every 150 miles or 3 hours thereafter.

Front-end structures are required to prevent cargo from shifting forward more than a set distance; rear-end structures protect against rearward shift.

Overweight or improperly loaded cargo affects braking, steering, and rollover risk; redistribute the load before driving.

Hazardous materials require a CDL with a hazmat endorsement, a Transportation Security Administration background check, and a placarded vehicle.

Placards must be displayed on all four sides of a vehicle carrying hazardous materials in quantities requiring placarding.

The hazardous materials endorsement requires a knowledge test and a security threat assessment; it must be renewed every 5 years.

A vehicle carrying hazardous materials must stop at railroad crossings, and must not be left unattended unless secured and the engine off.

Shipping papers must be within reach of the driver while seated, and must include the proper shipping name, hazard class, UN number, and quantity.

Explosives, radioactive materials, and certain poisons require special routing and may be prohibited from tunnels and certain bridges.

The emergency response guidebook (ERG) provides initial response information by guide number and must be carried when required.

A vehicle transporting hazardous materials must display the appropriate placards and may not carry passengers or incompatible materials.

Commercial vehicles must stop at railroad crossings unless the crossing is marked as exempt; stop 15-50 feet from the nearest rail.

Before crossing, look both ways, listen, and make sure the vehicle has enough room to clear the tracks completely on the other side.

Never stop on the tracks; if the vehicle stalls, get everyone out and move away from the tracks immediately.

A school bus must stop at all railroad crossings, open the door, and turn off noisy equipment to listen for trains.

School buses loading or unloading students display flashing red lights and an extended stop arm; traffic in both directions must stop except on divided highways.

School bus drivers must check for students before moving, and must not leave the bus with students aboard unattended.

The school bus stop arm and red lights must be used only when loading or unloading students; they must be retracted before moving.

When driving near a school bus, watch for children crossing the road and be prepared to stop even after the lights stop flashing.

The pre-trip inspection must be completed within the 24 hours before driving, and the driver must sign a report certifying the vehicle is safe.

Check coolant, oil, power steering fluid, and windshield washer fluid levels; look for leaks under the vehicle.

Belts should have no more than 3/4 inch of play at the longest span, and hoses must be free of cracks, leaks, and soft spots.

The air brake system must be checked for leaks, low pressure warning, and spring brake operation before each trip.

Check that all lights work: headlights, high beams, turn signals, brake lights, clearance lights, and hazard flashers.

Tires must be properly inflated, free of cuts and bulges, and have adequate tread depth; check dual tires for proper spacing.

The fifth wheel and kingpin must be inspected for cracks, wear, and proper locking; the release handle must be secured.

The emergency kit should include a fire extinguisher, warning triangles, and spare fuses; the fire extinguisher must be charged and mounted.

At an accident, stop, protect the scene, and check for injuries; call 911 and report the location and number of injured people.

Place warning triangles or flares behind the vehicle to warn traffic; use at least three devices spaced appropriately for the speed limit.

Do not move an injured person unless there is immediate danger such as fire or traffic.

Exchange information with the other driver: name, address, phone, license number, insurance, and vehicle registration.

Report the accident to the carrier immediately, and file a written report within the time required by the state, often 24-72 hours.

A driver must be tested for alcohol and drugs after a fatal accident or an accident requiring hospitalization, per federal rules.

Do not admit fault or discuss the accident with anyone except police, the carrier, and insurance representatives.

Record the accident scene: take photos, note skid marks, weather, and road conditions, and get names of witnesses.