District Of Columbia CDL DMV Endorsement Double 1

When driving a vehicle with air brakes, if the low air pressure warning light comes on, it is important for you to stop and safely park your vehicle as soon as possible. There may be a leak in the system. Controlled braking will remain possible only as long as there is enough air left in the tanks.

Correctly following the steps to couple and uncouple trailers is vital to safely operating a combination vehicle. After connecting the air lines to the trailer while coupling, you should supply air to the trailer.

Speeding up too quickly on a road with poor traction could cause a driver to lose control of their vehicle. In conditions that cause poor traction, a driver should accelerate especially smoothly and gradually.

Never apply the brake pedal if your spring breaks are activated. Brakes can be damaged if they are subject to both springs and air pressure.

If you must stop on the side of the road, it is important to turn on your four-way emergency flashers to warn other road users.

Federal and state laws require that CMV drivers inspect their vehicles before every trip.

Friction inside a brake drum is caused when the brake shoes and linings push against the inside of the drum. The friction in the drums will slow and stop the vehicle.

It is essential to safety that a driver inspects coupling before starting a trip. Trailer coupling on a double or triple combination can be tested by pulling against the pin of the second semi-trailer.

Be careful around pedestrians, joggers, and cyclists who are wearing headphones. They may not be able to clearly hear surrounding traffic and may not be aware that you are there.

Defects in an exhaust system are very dangerous because they can cause poisonous fumes to enter the cab or sleeper berth.

After a trip, you may be required to perform an inspection and file a report on each vehicle that you've driven.

Anti-Lock Braking Systems (ABS) will help you to maintain control during hard braking. ABS will not necessarily shorten your stopping distance.

If a tractor-trailer is so equipped, the trailer brake hand valve can be used to stop the vehicle from rolling back when being started from a stop.

When driving during the winter, it is particularly important that your tires have adequate tread. You need a tread depth of at least 4/32 of an inch in every major groove on the front tires, and at least 2/32 of an inch on the back tires. Check the tread depths by using a gauge.

Double and triple trailer combinations are more likely to turn over due to the "crack-the-whip" effect than are other combination vehicles. Drivers must steer gently when pulling trailers.

You should test the tractor protection valve by allowing the air supply to properly charge, turning off the engine, then releasing air from the system by pressing the brake pedal several times. The tractor protection valve should move into its emergency position when psi drops to an unsafe level.

If your vehicle "pulls" to one side when braking, you may have brake trouble. If there is an issue with your brakes, you should fix the issue before driving. Operating an unsafe vehicle is against federal and state laws.

If your trailer goes off course while you are backing, you should pull your truck forward and reposition your vehicle as needed before continuing to back up.

All commercial motor vehicles are required to be equipped with the proper emergency equipment. This may include spare electrical fuses; three red reflective triangles, six fuses, or three liquid burning flares; and at least one properly charged and rated fire extinguisher.

In an air brake system, a low pressure warning signal should activate if the pressure in the air tanks falls to a level below 60 psi. This signal may be in the form of a warning light or a wig wag.