CDL School

A hazard is any road condition or other road user (driver, bicyclist, pedestrian) that is a possible danger.

The governor controls when the air compressor will pump air into the air storage tanks. When air tank pressure rises to the "cut-out" level around 125 psi, the governor stops the compressor from pumping air. When the tank pressure falls to the "cut-in" pressure around 100 psi, the governor allows the compressor to start pumping again.

You must review the inspection report made by the previous driver. Only if defects reported earlier have been certified as repaired or not needed to be repaired, should you sign the previous driver's report.

Wedge brakes and disc brakes are less common than s-cam brakes.

Snub braking method is used for steep downhill grades, in this method apply the brakes just hard enough to feel a definite slowdown. When your speed has been reduced to approximately five mph below your "safe" speed, release the brakes. When your speed has increased to your "safe" speed, repeat.

Use windshield washer antifreeze to prevent freezing of the washer liquid.

When the low air pressure warning light and buzzer first come on, bring the vehicle to a safe stop right away, while you can still control the brakes.

It takes a typical tractor trailer unit at least 14 seconds to clear a single track and more than 15 seconds to clear a double track.

Whether or not you load and secure the cargo yourself, you are responsible for inspecting your cargo, recognizing overloads and poorly balanced weight, knowing your cargo is properly secured and does not obscure your view ahead or to the sides, knowing your cargo does not restrict your access to emergency equipment.

Watch for: vehicles that may drift over the lane divider lines or within their own lane; vehicles traveling at inconsistent speeds; drivers who are preoccupied with maps, food, cigarettes, cell phones, or other objects; drivers who appear to be involved in conversations with their passengers.

When driving a loud bang, vibrations, or heavy steering can indicate that a tire has failed.

The tire load is the maximum safe weight a tire can carry at a specified pressure. This rating is stated on the side of each tire.

Driving too fast is a major cause of fatal crashes. You must adjust your speed depending on driving conditions. These include traction, curves, visibility, traffic, and hills.

Hauling liquids in tanks requires special skills because of the high center of gravity and liquid movement.

Most vehicles now have an ABS light on the instrument panel that will light up briefly when the vehicle is started to alert you that the vehicle has ABS, you can check to see if the vehicle was built on or after March 1, 1998, or you can check for wires from your brakes.

You need at least 4/32-inch tread depth in every major groove on front tires. No fabric should show through the tread or sidewall. There should be no cuts or other damage.

The gross combination weight (GCW” is the total weight of the GCWs of each unit of a combination vehicle – truck/tractor and trailer(s) added together.

With the stab braking method, you apply your brakes all the way and release brakes when wheels lock up. 

Perception Distance + Reaction Distance + Brake Lag Distance + Braking Distance = Total Stopping Distance

Tire problems include: too much or too little air pressure, bad wear, at least 4/32-inch tread depth on front tires, 2/32 inch on all other tires, no fabric should show through the tread or sidewall, cuts or other damage, tread separation, dual tires that come in contact with each other or parts of the vehicle, mismatched sizes, radial and bias-ply tires used together.

 If possible, avoid using the brakes until your speed has dropped to about 20 mph, and gently return to the road.

Rear wheel braking skids occur when the rear drive wheels lock. Because locked wheels have less traction than rolling wheels, the rear wheels usually slide sideways in an attempt to "catch up" with the front wheels. With vehicles towing trailers, a drive-wheel skid can let the trailer push the towing vehicle sideways, causing a sudden jackknife.

Braking when a tire has failed could cause loss of control. Unless you're about to run into something, stay off the brakes until the vehicle has slowed down. Then brake very gently, pull off the road, and stop.

To know how much space you have, wait until the vehicle ahead passes a shadow on the road, a pavement marking, or some other clear landmark. Then count off the seconds like this: "one thousand-and-one, one thousand-and-two" and so on, until you reach the same spot.

Before you begin backing, work out a set of hand signals that you both understand. Agree on a signal for "stop."

Explanation: The gear box is part of the steering system, and other choices are parts of the suspension system.

While you are at the front of the vehicle, check the following items: headlight, low and high beam; windshield wiper arms for proper spring tension; wiper blades for damage; reflectors.

Air pressure increases with temperature. Do not let air out or the pressure will be too low when the tires cool off.

Inspect the tires more often than usual, or every two hours or every 100 miles when driving in very hot weather.

Before you change lanes, you must first make sure that no vehicles are hiding in your blind spots.

Heavy vehicles are often tailgated when they can't keep up with the speed of traffic. This often happens when you're going uphill. If a heavy load is slowing you down, stay in the right lane if you can. Going uphill, you should not pass another slow vehicle unless you can get around quickly and safely.

Never leave your vehicle unattended without applying the parking brakes or chocking the wheels. Your vehicle might roll away and cause injury and damage.

Without ABS you still have normal brake functions. Drive and brake as you always have.

Explanation: Use high beams when it is safe and legal to do so. Use them when you are not within 500 feet of an approaching vehicle. 

Your CDL will be disqualified after two or more convictions of any state law on texting while operating a CMV. No motor carrier shall allow or require its drivers to engage in texting while driving.

Explanation: A skid happens whenever the tires lose their grip on the road. Most serious skids result from driving too fast for road conditions. Drivers who adjust their driving to conditions don't over-accelerate and don't have to over-brake or oversteer from too much speed. 

Protect the accident area: if your vehicle is involved in the accident, try to get it to the side of the road, if you're stopping to help, park away from the accident, put on your flashers, and set out reflective triangles to warn other traffic.

If you find yourself being tailgated: avoid quick changes, signal early, reduce speed very gradually, increase your following distance, and don't speed up.

Strong winds make it difficult to stay in your lane. The problem is usually worse for lighter vehicles. This problem can be especially bad coming out of tunnels.

Slow down to a safe speed, and downshift to the right gear before entering the curve. This lets you use some power through the curve to help the vehicle be more stable while turning. It also allows you to speed up as soon as you are out of the curve.

A stale green light is a traffic light that is green when you first see it, thus you do not know how long it has been green - so we have to assume it will change at any moment.

Commercial vehicle must be equipped with 3 red reflective triangles, 6 fuses or 3 liquid burning flares.

Air brakes are three different systems: service brake, parking brake, and emergency brake.

Empty trucks actually require greater stopping distances because an empty vehicle has less traction. It can bounce and lock up its wheels, giving much poorer braking.

Do not try to downshift after your speed has already built up. You will not be able to shift into a lower gear. You may not even be able to get back into any gear and all engine braking effect will be lost.

If an oncoming driver has drifted into your lane, a move to your right is best. If that driver realizes what has happened, the natural response will be to return to their own lane. No one is likely to be driving on the shoulder, but someone may be passing you on the left.

The total stopping distance is the total minimum distance your vehicle has traveled, in ideal conditions; with everything considered, including perception distance, reaction distance and braking distance, until you can bring your vehicle to a complete stop. At 55 mph, your vehicle will travel a minimum of 450 feet.

You will lose your CDL for at least one year for a first offense for: Driving a CMV if your blood alcohol concentration is .04% or higher or driving a CMV under the influence of alcohol.

¾ second to 1 second.