Maryland CDL General Knowledge flashcards

32 cards. Read the term and the definition here. The deck at the top of this page is optional.

Total stopping distance

The sum of perception distance, reaction distance, brake lag distance, and braking distance. It increases with speed and weight, and braking distance grows with the square of speed.

Maryland CMV BAC limit

A commercial driver operating a CMV is considered under the influence at 0.04% BAC in Maryland. A CDL holder can be placed out of service for 24 hours at that level.

Following distance rule

Allow one second for each 10 feet of vehicle length, plus one second for speeds above 40 mph. A 60-foot combination at 55 mph needs at least seven seconds.

Railroad crossing stop distance

Vehicles carrying passengers or hazardous materials must stop 15 to 50 feet before the nearest rail, open the door or window, listen, and never shift gears while crossing.

Hydroplaning speed

Hydroplaning can begin at about 30 mph when tires ride on a film of water. Worn tires and higher speeds increase the risk, and steering and braking become ineffective.

Governor cut-in and cut-out

The air compressor 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.

Low air pressure warning

The warning device must activate before pressure drops below 60 psi. At that point the spring brakes begin to apply automatically as pressure continues to fall.

Static air leak test

With the engine off and full pressure, release the service brake and watch the gauge. A drop of more than 3 psi per minute for a single vehicle or 4 psi for a combination indicates a leak.

Applied air leak test

Hold the service brake fully applied for one minute with the engine off. A drop of more than 4 psi for a single vehicle or 6 psi for a combination indicates a leak.

Slack adjuster free play

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

Tractor protection valve

The valve closes the tractor air lines when trailer pressure drops to about 45 psi. This applies the trailer spring brakes and prevents air loss if the trailer separates.

Fifth wheel tug test

After backing under the trailer, set the trailer brakes and pull forward gently. If the tractor moves without the trailer, the fifth wheel is not locked; check the jaws and handle.

Trailer air line colors

The emergency or supply line is typically red and the service line is blue. Crossed lines can lock the trailer brakes or prevent them from releasing.

Off-tracking

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

Rearward amplification

The last trailer in a double or triple swings wider than the tractor during a lane change. Slower, smoother steering inputs reduce the risk of a rollover or lane departure.

Hazard class 3

Class 3 covers flammable and combustible liquids, such as gasoline and diesel fuel. Placards are required for 1,001 pounds or more in a vehicle.

Shipping paper contents

The shipping paper must show the proper shipping name, hazard class, UN or NA identification number, packing group, and total quantity of the hazardous material.

Hazmat 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.

Segregation of cyanides and acids

Cyanides and acids must never be loaded together because they can react to form deadly gas. Oxidizers must also be separated from flammables.

Minimum tiedown count

One tiedown for cargo up to 5 feet and 1,100 pounds; two for cargo over 5 feet or over 1,100 pounds; four for cargo over 10,000 pounds.

Aggregate working load limit

The combined working load limit of all tiedowns must be at least 50% of the cargo weight. Each tiedown must be rated and attached to a rated anchor point.

Cargo recheck interval

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.

Standee line

The line on a passenger bus marking where standing passengers may not cross. No passenger may stand forward of that line while the bus is moving.

Passenger railroad crossing stop

A bus carrying passengers must stop 15 to 50 feet before the nearest rail, open the door or window, and listen before crossing the tracks.

Passenger baggage storage

Baggage must be stored so it cannot block the aisle or emergency exits. Riders may not carry hazardous or bulky items that obstruct movement.

School bus danger zone

The area within 10 feet around the school bus is the most dangerous. Students must be visible to the driver at all times when boarding or leaving.

School bus railroad crossing

A school bus must stop at all railroad crossings, open the door, and turn off noisy equipment before crossing. The driver listens and looks before proceeding.

Child-check procedure

The driver must check the bus for sleeping children after every run. The child-check reminder system and a walk-through of the bus are required at the end of each route.

Tanker outage

Outage, or ullage, is the empty space left at the top of a tank for liquid expansion. Leave about 1% to 2% of tank volume empty when loading.

Baffled versus smooth bore

Baffles divide the tank into compartments to slow liquid movement. Smooth bore tanks have no baffles and are more prone to surge, so they require lower speeds.

Converter dolly safety chains

The 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.

Doubles 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 and check all air lines and chains.