Maryland CDL General Knowledge cheat sheet

Pre-trip inspection order: engine compartment (fluid levels, belts, hoses, steering, exhaust, leaks), then walk-around (lights, tires, wheels, mud flaps, frame), then in-cab (gauges, horn, wipers, mirrors, emergency equipment).

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

Maryland legal BAC limit is 0.04% for commercial drivers operating a CMV and 0.08% for non-commercial vehicles; a CDL holder can be put out of service for 24 hours at 0.04% or higher.

Speed management: reduce speed by at least 10 mph below the posted limit on wet roads, and by one-third on packed snow; on ice, cut speed to a crawl and avoid any sudden steering or braking input.

Following distance rule: one second per 10 feet of vehicle length plus one second for speeds above 40 mph; a 60-foot combination at 55 mph needs at least 7 seconds.

Shifting: upshift progressively through the range, never coast in neutral, and use the splitter or range selector only after the transmission is in the correct gear for the road speed.

Backing: back only when necessary, use a helper or get out and check, back toward the driver's side (left) when possible, and stop immediately if you lose sight of the helper.

Railroad crossing: stop 15 to 50 feet before the nearest rail when carrying passengers or hazardous materials, and never shift gears while crossing the tracks.

Fatigue: after 8 cumulative hours without a 30-minute interruption, take a break; hours-of-service limits for property-carrying drivers are 11 hours driving and 14 hours on duty after 10 consecutive hours off.

Air brake system components: compressor, governor, air storage tanks, drain cocks, safety valve, foot valve, slack adjusters, brake chambers, and the low-pressure warning device.

The governor cuts the compressor in at about 85 psi and out at about 100 psi; the safety valve releases at about 150 psi to protect the tanks.

The low air pressure warning must activate before pressure drops below 60 psi; at that point the spring brakes begin to apply automatically.

Static leak test: with the engine off and full pressure, release the service brake and watch for a pressure drop of more than 3 psi in one minute (single vehicle) or 4 psi (combination).

Applied leak test: hold the service brake fully applied for one minute; a drop of more than 4 psi (single) or 6 psi (combination) indicates a leak.

The tractor protection valve and trailer air supply valve close automatically when trailer pressure drops to about 45 psi, applying the trailer spring brakes.

Slack adjusters should have no more than about 1 inch of free play at the push rod; check the 90-degree angle between the push rod and slack adjuster at full brake application.

The supply pressure gauge shows compressor/tank pressure; the application pressure gauge shows how much pressure you are applying with the foot valve.

Fifth wheel coupling check: after backing under the trailer, tug-test by pulling forward gently with the trailer brakes set, then visually confirm the jaws are closed around the kingpin and the release handle is in.

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

Landing gear must be fully raised after coupling; if the trailer is loaded, raise the gear before the tractor is fully under load to avoid damage.

Off-tracking: a combination vehicle's rear wheels follow a shorter path than the front; the longer the wheelbase, the greater the off-track, so swing wide on right turns.

Rearward amplification: the last trailer in a set swings wider than the tractor during a lane change; doubles and triples require slower, smoother steering inputs.

Bobtail (tractor without trailer) braking is poor because the tractor's light rear axle has little weight; allow extra stopping distance and brake gently.

Rollover risk rises with a high center of gravity; posted curve speeds are advisory for cars, so reduce speed further for a loaded combination.

Hazard classes: 1 explosives, 2 gases, 3 flammable liquids, 4 flammable solids, 5 oxidizers, 6 toxic/infectious, 7 radioactive, 8 corrosives, 9 miscellaneous.

Placards are required for 1,001 pounds or more of a hazard class in a vehicle, and for any amount of certain materials such as 2.3 toxic gas or 6.1 PG I.

The shipping paper must include the proper shipping name, hazard class, UN/NA identification number, packing group, and total quantity.

An emergency response information sheet must accompany the shipping paper; the ERG (Emergency Response Guidebook) is organized by guide number and by UN/NA number.

Segregation: cyanides and acids must never be loaded together; oxidizers must be separated from flammables; consult the segregation table before loading.

Parking rules: never park within 5 feet of a roadway, and never park within 300 feet of a bridge, tunnel, or open flame when carrying hazardous materials.

For a hazardous materials spill, stop, secure the scene, call for help, and stay upwind; do not attempt cleanup unless trained and authorized.

Aggregate working load limit of the tiedowns must be at least 50% of the cargo weight; each tiedown must be rated and attached to the vehicle frame or a rated anchor point.

Minimum tiedown count: one for cargo up to 5 feet and 1,100 pounds; two for cargo over 5 feet or over 1,100 pounds but under 10,000 pounds; four for cargo over 10,000 pounds.

The cargo must be secured so it cannot shift more than 1 inch forward or backward and cannot tip or slide sideways.

Front-end structure requirement: cargo must be loaded against the headboard or secured to prevent forward movement; heavy articles should be placed near the floor and toward the front.

Inspect cargo and tiedowns within the first 50 miles of a trip and every 150 miles or 3 hours thereafter, and after any emergency stop.

Flags or reflective devices are required on loads that extend more than 4 feet beyond the rear of the vehicle, and the load must not exceed state length limits.

Never overload an axle; check the gross vehicle weight rating and the axle weight ratings before loading, and redistribute if a scale shows an overload.

Before driving, check the interior: seats, standee line, emergency exits, fire extinguisher, first aid kit, and restroom (if equipped); ensure aisles are clear.

The standee line marks where standing passengers may not cross; no passenger may stand forward of that line while the bus is moving.

Carry no more passengers than the seated and standing capacity shown on the seating chart; count passengers at each stop to avoid leaving someone behind.

At a railroad crossing with passengers aboard, stop 15 to 50 feet before the nearest rail, open the door or window, and listen before proceeding.

Loading and unloading: stop close to the curb, set the parking brake, and supervise boarding; do not move until all passengers are seated or holding a handrail.

Passenger baggage must be stored so it cannot block the aisle or emergency exits; do not allow riders to carry hazardous or bulky items.

If a passenger becomes ill or unruly, stop safely, address the situation, and call dispatch; never leave the vehicle unattended with passengers aboard.

School bus pre-trip adds: stop arm, flashing red and amber lights, crossing gate, child-check buzzer, and the emergency exit door alarm.

Loading and unloading: activate the amber warning lights, stop, then activate the red lights and stop arm; students cross only after the driver signals them.

Students must cross in front of the bus and wait for the driver's hand signal; the driver counts students as they board and as they leave.

Danger zone: the area within 10 feet around the bus is the most dangerous; students must be visible to the driver at all times.

Maryland school buses must stop at all railroad crossings, open the door, and turn off noisy equipment before crossing.

The driver must check the bus for sleeping children after every run; the child-check procedure is required at the end of each route.

Emergency evacuation: stop, set the brake, turn off the engine, and use the rear door or side door; account for all students at a safe distance from the bus.

Tankers have a high center of gravity; liquid surges forward, backward, and sideways, so reduce speed before curves and brake gently.

Baffles divide the tank into compartments to slow liquid movement; unbaffled tanks require even lower speeds and smoother steering.

The tank must have a manhole cover, a vent, and a spill dam; check that the dome cover is closed and the vent is open before moving.

Outage (ullage) is the empty space at the top of the tank; leave enough outage for liquid expansion, typically about 1% to 2% of tank volume.

Load limits are based on product density; a tank rated for water can be overloaded by a heavier product, so check the weight before filling.

Smooth bore tanks have no baffles and are especially prone to surge; divide the load or slow down to reduce the effect.

After loading, close all valves and check for leaks; never smoke or use open flame near the tank, and ground the vehicle during transfer of flammables.

Converter dolly: a frame with a fifth wheel and a pintle hook that couples the first trailer to the second; check the pintle hook, safety chains, and air lines.

Coupling order: couple the tractor to the first trailer, then back the dolly under the second trailer, then connect the dolly to the first trailer.

Safety chains must be crossed under the dolly tongue and hooked to the towing vehicle; they prevent the dolly from dropping if the pintle hook fails.

The shut-off valve on the dolly's air line must be open; closed valves prevent the trailer brakes from releasing or applying correctly.

Doubles and triples require more space for turns and stops; the last trailer off-tracks the most, so swing wide and check mirrors constantly.

The maximum combination length in Maryland is 28 feet per trailer for doubles on designated routes; check route restrictions before driving.

Before driving, test the brakes on each unit separately: with the trailer brakes applied, the tractor should not move; with the tractor brakes applied, the trailer should not move.

The pre-trip inspection must be completed within the last 24 hours before driving; the driver signs the report and notes any defects.

Hydroplaning occurs when tires ride on a film of water; it begins at about 30 mph with worn tires and increases with speed and low tread depth.

Night driving: use low beams within 500 feet of an oncoming vehicle and within 200 feet when following; high beams should be dimmed in fog, rain, or snow.

Mountain driving: use a lower gear before descending, do not ride the brakes, and use engine braking; if brakes fade, pull over and let them cool.

The escape ramp is for runaway trucks on steep downgrades; aim for the gravel or sand pile if brakes fail.

Alcohol: a 12-ounce beer, 5-ounce glass of wine, and 1.5-ounce shot of liquor all contain about the same amount of alcohol.

The CDL disqualification for a first DUI in a CMV is one year; a second offense results in a lifetime disqualification.

The air compressor is engine-driven and must build pressure from 85 to 100 psi within 45 seconds at fast idle; a slower build indicates a problem.

The alcohol evaporator or air dryer removes moisture from the air system; drain the tanks daily to prevent freeze-ups in cold weather.

The spring brakes apply automatically when air pressure is lost; they are held off by air pressure, so a loss of air means the brakes engage.

The parking brake control (yellow diamond knob) is pushed in to release and pulled out to apply; the trailer air supply (red octagon) controls the trailer.

The brake pedal is the foot valve; a light, steady application is best, and the pedal should not be pumped on a long downgrade.

If the low-pressure warning sounds, stop as soon as it is safe; the spring brakes will apply when pressure drops to about 20 to 45 psi.

The air brake check includes a test of the low-pressure warning, the spring brake application, and the rate of pressure buildup.

The kingpin is the pin on the trailer that locks into the fifth wheel jaws; a worn or damaged kingpin can cause the trailer to separate.

The gap between the tractor and trailer should be checked after coupling; a visible gap means the fifth wheel is not fully locked.

The trailer hand valve (Johnson bar) is used only for testing trailer brakes; it should not be used for normal braking because it can cause a skid.

The tractor protection valve prevents air loss from the tractor if the trailer breaks away; it closes the lines when pressure drops to about 45 psi.

The air lines should be supported so they do not drag; a dragging line can be cut and cause a loss of trailer brakes.

When uncoupling, set the trailer brakes, lower the landing gear, disconnect the air lines and electrical cord, then release the fifth wheel and pull forward slowly.

A combination vehicle with a loaded trailer has a longer stopping distance than a bobtail; the heavier the load, the more distance is needed.

A hazardous materials endorsement requires a TSA security threat assessment and a knowledge test; the endorsement is marked on the CDL.

The driver must carry the shipping paper within reach while driving and must be able to produce it for inspection.

Placards must be visible from all four sides of the vehicle; they are placed on both sides and both ends of the vehicle.

The DOT hazardous materials response guide number is printed on the shipping paper; the ERG lists the guide by UN/NA number.

A vehicle carrying hazardous materials must be attended at all times unless parked in a secure location; unattended vehicles must have the brakes set and the keys removed.

Route restrictions: hazardous materials may be banned from tunnels, bridges, and certain highways; check the route before departure.

Report a spill immediately to the National Response Center at 1-800-424-8802 and to the local emergency responders.

The headboard must be strong enough to stop the cargo from moving forward; it should be at least as high as the cargo.

Tiedowns must be attached to the frame or to a rated anchor point, not to the sheet metal or to the cargo itself.

The working load limit of a tiedown is the maximum load it can carry; it is usually stamped on the chain, strap, or binder.

Chains and binders must be tight; a loose tiedown can snap and injure someone, so use a cheater bar or binder to take up slack.

Cargo must not cover the lights, reflectors, or license plate; if it does, add auxiliary lights and a flag.

The cargo must be checked after the first 50 miles and every 150 miles or 3 hours; a load can shift as the vehicle settles.

A load that is 4 feet or more beyond the rear must have a red flag or reflective device during the day and a red light at night.

The bus must have a fire extinguisher, first aid kit, and emergency exit markings; check that the exits open freely and the alarms work.

The aisle must be kept clear of baggage and standees; a blocked aisle slows evacuation in an emergency.

The driver must announce stops and check for passengers before closing the door; a passenger can be caught in the door or left behind.

The bus must stop at least 15 feet from the nearest rail at a railroad crossing; open the door and listen before crossing.

The driver should not allow passengers to stand in front of the standee line or on the stairwell while the bus is moving.

In an emergency, evacuate passengers to a safe distance and call for help; account for all passengers before leaving the scene.

The bus driver must not drive more than 10 hours after 8 hours off duty; passenger-carrying rules follow the hours-of-service limits.

The school bus stop arm and red lights must be used when loading or unloading students on a roadway; amber lights warn of an approaching stop.

The driver must ensure students are seated and the aisle is clear before moving the bus.

The bus must be equipped with a crossing gate or a stop arm; the driver signals students to cross only after traffic has stopped.

The driver must check the bus for sleeping children after each run and use the child-check reminder system.

The danger zone is the area within 10 feet of the bus; students must be visible to the driver at all times.

The school bus must stop at all railroad crossings, open the door, and turn off the radio and heater before crossing.

The driver must report any accident, injury, or misconduct to the school district immediately.

The tank must be marked with the product name and the hazard class; the placard must match the product being carried.

The tank must have a pressure relief valve and a vent; a clogged vent can cause the tank to rupture.

The tank must be grounded before loading or unloading flammable liquids; the ground wire must be connected to the tank and to a ground source.

The tank must not be overfilled; leave outage space for expansion, and check the weight against the axle ratings.

The tank must be inspected for leaks, cracks, and loose fittings before each trip; a leak can cause a spill or a fire.

The driver must avoid sudden stops and sharp turns when carrying a partial load; the liquid can surge and cause a rollover.

The tank must be cleaned and purged before changing products; a residue can react with the new product.

The dolly must be equipped with a fifth wheel, a pintle hook, safety chains, and air lines; check all before coupling.

The safety chains must be crossed under the dolly tongue and hooked to the towing vehicle; they prevent the dolly from dropping if the pintle hook fails.

The air line shut-off valves must be open; a closed valve prevents the trailer brakes from releasing or applying correctly.

The dolly must be backed under the second trailer until the fifth wheel locks; then tug-test to confirm the coupling.

The combination must be checked for length and route restrictions; doubles and triples are not allowed on all roads.

The last trailer off-tracks the most; swing wide on turns and check mirrors constantly.

The driver must test the brakes on each unit separately before driving; a unit with faulty brakes must be repaired before use.