Colorado CDL General Knowledge cheat sheet

Pre-trip inspection: check the engine compartment, walk-around, and in-cab items; any defect affecting safe operation keeps the vehicle out of service until repaired.

Class A CDL covers combination vehicles over 26,000 lb GCWR with a towed unit over 10,000 lb; Class B covers single vehicles over 26,000 lb; Class C covers vehicles designed for 16+ passengers or placarded hazmat below Class A/B thresholds.

Stopping distance = perception distance + reaction distance + braking distance; total stopping distance grows with the square of speed, so doubling speed roughly quadruples braking distance.

Following distance rule: at least one second per 10 feet of vehicle length plus one second at speeds above 40 mph; maintain a 4-second gap below 40 mph and 5 seconds or more above.

Speed limits in Colorado: 75 mph on many rural interstates, 65 mph in urban areas, 55 mph on two-lane highways unless posted otherwise; always obey posted signs and conditions.

Blood alcohol concentration of 0.04% or higher in a CMV is disqualifying; a CDL holder refusing a chemical test is disqualified for at least one year for a first offense.

Railroad crossing: stop between 15 and 50 feet from the nearest rail if the vehicle carries hazmat, passengers, or is a school bus; look and listen before proceeding.

Tire defects: minimum tread depth is 4/32 inch for front steer tires and 2/32 inch for all other tires; sidewall cuts, bulges, or exposed cords put the vehicle out of service.

Downshift before a downgrade and use engine braking; Colorado mountain grades require choosing a gear that holds speed without continuous service brake use to prevent brake fade.

Air brake system components: compressor, governor, air tanks (wet, primary, secondary), safety valve, drain valves, foot valve, slack adjusters, brake chambers, and spring/parking brakes.

Pressure build-up test: with the engine at operating rpm, pressure should rise from 85 to 100 psi within 45 seconds; a slower rise indicates a compressor or leak problem.

Static leak test: with the engine off and full pressure, pressure loss must not exceed 3 psi per minute for a single vehicle or 4 psi per minute for a combination.

Applied leak test: hold the brake pedal fully down; leakage must not exceed 4 psi per minute for a single vehicle or 6 psi per minute for a combination.

Low-air warning: the warning buzzer and light must activate before pressure drops below 60 psi; the spring brakes must fully apply by 20-45 psi.

Governor cut-out is typically around 120-140 psi and cut-in around 100 psi; the safety valve releases near 150 psi to protect the system.

Slack adjusters: with the brakes released and pushed by hand, the adjustment limit is about 1 inch of travel on a standard chamber; automatic slack adjusters must not be manually readjusted except during repair.

Brake fade: continuous use of service brakes on a long downgrade overheats drums and reduces braking; select a lower gear and use intermittent braking to control speed.

Fifth-wheel coupling check: after coupling, pull the tractor forward gently with the trailer brakes set; the trailer must not move if the jaws are locked.

Tug test alone is not proof of a locked fifth wheel; verify visually that the locking jaws are closed around the kingpin and that the release handle is in the locked position.

Trailer air lines: the emergency (supply) line is typically red and the service line is blue; crossed lines cause the trailer brakes to lock or fail to release.

Landing gear must be fully raised before driving; if it contacts the ground, the trailer can be damaged and stability compromised.

Off-tracking: the rear wheels of a combination follow a shorter path than the front wheels, so right turns require swinging wide and checking mirrors for the trailer's rear.

Rearward amplification (crack-the-whip) increases with speed and with the number of trailers; triple trailers are the most susceptible to rollover during rapid lane changes.

Trailer sway or fishtail: release the accelerator and steer straight rather than braking hard, which can worsen the oscillation.

Turn signals must be canceled automatically or manually after a turn; check that the trailer's brake and turn lights operate during the pre-trip inspection.

Placards are required for shipments of 1,001 lb or more aggregate gross weight of a hazard class; bulk packages require placards regardless of weight.

Hazard class numbers: 1 explosives, 2 gases, 3 flammable liquids, 4 flammable solids, 5 oxidizers, 6 toxic, 7 radioactive, 8 corrosive, 9 miscellaneous.

Shipping papers must be within reach of the driver while seated, kept in a clearly marked holder, and include the basic description, quantity, and emergency response phone number.

A CDL hazmat endorsement requires a TSA security threat assessment, a knowledge test, and a valid medical certificate; the endorsement must be renewed with the background check.

Parking rules: do not park within 5 feet of the traveled portion of a road, and never park near an open flame, bridge, tunnel, or crowded place unless attended.

Smoking and open flames are prohibited within 25 feet of a vehicle carrying explosives, oxidizers, or flammable materials; the engine must be shut off during fueling.

Emergency response: use the ERG guide number from the shipping paper, keep people upwind and uphill, and do not attempt to fight a fire involving explosives or unknown materials.

A hazardous materials incident must be reported to the carrier and to emergency responders; the driver must not move the vehicle if it creates additional risk.

Liquid surge: a partially filled tank allows the load to shift forward on braking and rearward on acceleration, increasing stopping distance and rollover risk.

Baffles divide the tank into compartments to slow liquid movement; baffled tanks still surge, so smooth braking and gentle steering are required.

Tankers have a higher center of gravity than dry vans; rollovers occur at lower lateral acceleration, so reduce speed in curves and on ramps.

Bulk liquid outlets must be closed and secure before moving; check that hatches are closed and that the tank is not leaking at the pre-trip inspection.

Cargo tank vehicles carrying flammable liquids must have a fire extinguisher rated at least 10 BC; check the gauge and mounting before departure.

The smooth bore tanker braking rule: stopping distance increases with speed and liquid movement; leave a following gap larger than for a comparable dry van.

Curves: enter at or below the posted advisory speed and accelerate gently through the curve; braking while turning can cause the liquid to shift and tip the vehicle.

Tank vehicle endorsement (N) is required for tanks over 1,000 gallons; a tanker carrying hazardous materials also requires the hazmat endorsement (H or X).