CDL School

Explanation: A safety relief valve is installed in the first tank the air compressor pumps air to. The safety valve protects the tank and the rest of the system from too much pressure. The valve is usually set to open automatically at 150 psi. 

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

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

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.

Inspect the cargo and its securing devices again within the first 50 miles after beginning a trip. You need to inspect again after you have driven for 3 hours or 150 miles and after every break you take while driving.

When people are working on the road, it is a hazard. There may be narrower lanes, sharp turns, or uneven surfaces.

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.

Explanation: Don't roll back when you start. You may hit someone behind you. If you have a manual transmission vehicle, partly engage the clutch before you take your right foot off the brake. Put on the parking brake whenever necessary to keep it from rolling back. Release the parking brake only when you have applied enough engine power to keep from rolling back 

¾ second to 1 second.

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.

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

If for any reason you get stuck on the tracks, get out of the vehicle and away from the tracks. Check signposts or signal housing at the crossing for emergency notification information. Call 911 and give the location of the crossing using all identifiable landmarks, especially the DOT number, if posted.

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.

ABS helps you avoid wheel lock up and maintain control. You will not be able to use stab braking on a vehicle equipped with ABS.

Some vehicles have sight glasses, see-through coolant overflow containers, or coolant recovery containers. These permit you to check the coolant level while the engine is hot. If the container is not part of the pressurized system, the cap can be safely removed, and coolant added even when the engine is at operating temperature.

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.

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.

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.

Low air warning devices (buzzer, light, flag) should activate before air pressure drops below 60 psi or level specified by the manufacturer.

The Gross Vehicle Weight Rating (GVWR) is the value specified by the manufacturer as the loaded weight of a single vehicle.

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. 

Basic method for shifting up: release accelerator, push in clutch and shift to neutral at the same time. Release clutch. Let the engine and gears slow down to the rpm required for the next gear. Push in clutch and shift to the higher gear at the same time. Release clutch and press accelerator at the same time.

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

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. 

Blocking is used in the front, back, and/or sides of a piece of cargo to keep it from sliding. Blocking is shaped to fit snugly against cargo. It is secured to the cargo deck to prevent cargo movement.

Accident statistics show that the chance of a crash is much greater for drivers who have been drinking than for drivers who have not.

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.

Cargo should have at least one tie-down for each ten feet of cargo. You will need two tie downs for a 20-foot load.

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.

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.

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

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 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.

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.

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

Do the following to correct a drive-wheel braking skid: stop braking letting the rear wheels roll again and keep the rear wheels from sliding; counter-steer as a vehicle turns back on course, it tends to keep on turning. Unless you turn the steering wheel quickly the other way, you may find yourself skidding in the opposite direction.

Too much weight on the steering axle can cause hard steering. It can damage the steering axle and tires.

You should brake in a way that will keep your vehicle in a straight line and allow you to turn if it becomes necessary. You can use the "controlled braking" method or the "stab braking" method. 

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.

Shut off the engine and take the key with you so someone else won't move the truck while you are under it.

No matter how small the cargo, it should have at least two tie-downs.

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.

Don't over steer, over accelerate, or over brake by adjusting to conditions while driving. These include traction, curves, visibility, traffic and hills.

In some weather, water or slush collects on the road. When this happens, your vehicle can hydroplane. The tires lose contact with the road and have little or no traction. You may not be able to steer or brake. Hydroplaning can occur at speeds as low as 30 mph. Hydroplaning is more likely if tire pressure is low, or the tread is worn.

Short breaks can keep your alert. But the time to take them is before you feel really drowsy or tired. Stop often. Walk around and inspect your vehicle. It may help to do some physical exercise.

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

In a front-wheel skid, the front end tends to go in a straight line regardless of how much you turn the steering wheel. On a very slippery surface, you may not be able to steer around a curve or turn.

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