CDL flashcards

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

CDL weight threshold

A CDL is required to drive a combination vehicle with a gross combination weight rating of 26,001 pounds or more when the towed unit exceeds 10,000 pounds.

Following distance rule

Below 40 mph, allow one second for every 10 feet of vehicle length; add one second when traveling above 40 mph.

Total stopping distance

The sum of perception distance, reaction distance, brake lag distance, and braking distance; at 55 mph perception and reaction each cover about 60 feet.

Tire tread minimums

Front tires on a commercial vehicle need at least 4/32 inch of tread depth, and all other tires need at least 2/32 inch.

Safety valve setting

The safety valve on the air reservoir opens near 150 psi to release pressure and protect the system from overpressurization.

Low air pressure warning

A buzzer or light must warn the driver before air pressure drops below 60 psi, because braking power is being lost.

Spring brake application

Parking spring brakes apply automatically when system air pressure falls to about 20 to 45 psi.

Governor cut-in and cut-out

The governor switches the compressor on near 100 psi and off near 125 psi, keeping reservoir pressure within the operating range.

Fifth wheel tug test

With the trailer brakes locked, pull gently forward in a low gear; the tractor should not move if the kingpin is properly locked.

Glad hand colors

The red glad hand is the emergency line that supplies air to the trailer; the blue one is the service line that carries brake signals.

Tractor protection valve

It closes automatically when a trailer breaks away or an air line separates, trapping the tractor's air supply so the tractor can still stop.

Trailer hand valve

The trailer hand valve, also called the trolley valve, is used only to test trailer brakes and must never be used for parking.

Converter dolly

A frame with one or two axles, its own fifth wheel, a pintle eye, and safety chains that couples a second trailer to the first.

Rearward amplification

In doubles and triples the last trailer swings wider and travels faster through a turn than the tractor, so slow down and steer smoothly.

Dolly safety chains

Cross the dolly safety chains under the dolly tongue and hook them to the towing trailer so the dolly cannot drop to the road.

Trailer shut-off valves

Each trailer has shut-off valves on its air lines; close them before uncoupling so the trailer retains air and its spring brakes stay applied.

Liquid surge

The shift of liquid inside a partly filled tank that changes weight distribution and can push the vehicle forward, sideways, or into a rollover.

Outage

The empty space deliberately left in a tank so the liquid can expand as temperature rises; overfilling leaves no room and can rupture the tank.

Baffle

A wall inside a tank that slows the movement of liquid; baffles reduce surge but never remove it completely.

Smooth bore tank

A tank without baffles, where liquid moves freely; it demands lower speeds and gentle starts and stops, and often a special permit.

Placard weight thresholds

Placards are required at 1,001 pounds aggregate gross weight for Table 1 materials and 2,205 pounds for Table 2 materials.

Shipping papers access

Hazardous materials shipping papers must be kept within the driver's reach, such as in a pouch on the door or in clear view.

Hazmat parking rule

Never park a placarded vehicle within 5 feet of the traveled roadway, and keep it away from open fires and crowded places.

Emergency Response Guidebook

The ERG provides guide numbers, isolation distances, and first-aid steps for hazardous materials; use it with the shipping papers and placards.

Standee line

A line on the floor of a bus; no passenger may stand forward of it while the bus is moving.

Bus railroad crossing stop

Buses carrying passengers must stop between 15 and 50 feet from the nearest rail and check the tracks before crossing.

Passenger count and check

Count riders as they leave and walk the aisle checking seats for sleeping or hiding passengers before securing the bus.

Bus evacuation

Move riders well away from traffic and fire, use emergency exits, and send someone to flag down help.

Seven-step inspection

A pre-trip routine covering the engine compartment, the walk-around items, brake checks, and lights; it usually takes 15 to 30 minutes.

Static air leak test

With the system fully charged and the engine off, pressure loss should be under 3 psi per minute for a single vehicle and 4 psi for a combination.

Skid recovery

Steer in the direction you want the front of the vehicle to go and ease off the brakes so the tires can regain traction.

Downshifting on downgrades

Select a lower gear before starting down a steep grade so engine braking controls speed and the service brakes do not overheat.