Colorado CDL DMV Combination 1

Large combination vehicles take longer to stop when they are empty than when they are loaded. The decreased weight causes a vehicle's wheels to have decreased traction on the surface of the road.

If you are operating a vehicle built before 1998 and are unsure if the trailer has an Anti-Lock Braking System (ABS), you can check under the trailer for wheel speed sensors coming from the back of the brakes.

When coupling glad hands, make sure to couple together matching glad hands. To help drivers avoid mistakes, color coding is sometimes used. Service lines are often coded with the color blue and emergency lines are often coded with the color red.

To lower the risk of a rollover, load your cargo as closely to the ground as possible. To further reduce this risk, take curves and corners slowly.

Before a trip, be sure to inspect all couplings. There should be no space between the upper and lower fifth wheel.

Trailers and converter dollies built on or after March 1, 1998 are required to have Anti-Lock Braking Systems (ABS). This will be indicated by the presence of a yellow malfunction lamp. You can determine if older trailers have ABS by checking under the trailers for ECU and wheel speed sensor wires coming from the back of the brakes.

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.

In general, the parts of the service air line are coded blue and the parts of the emergency air line are coded red.

Push in the trailer air supply control to supply the trailer with air. Pull out the trailer air supply control to turn off the air supply and activate the emergency brakes.

Because the weight of cargo gives them a higher center of gravity, fully-loaded rigs are 10 times more likely to roll over in a crash than empty rigs.

Trailers built before 1975 are not required to have spring brakes. When parking a trailer without spring brakes, be sure to use wheel chocks to prevent the trailer from rolling.

On newer vehicles, the trailer air supply control is an eight-sided red knob. It's used to control the tractor protection valve.

Trailers and converter dollies manufactured on or after March 1, 1998 are required to have Anti-Lock Braking Systems (ABS).

The function of an Anti-Lock Braking System (ABS) is to prevent a vehicle's wheels from locking up during hard braking.

When backing with a trailer, turn the top of the steering wheel in the direction opposite of where you want to go. Once the trailer begins turning, you should then switch the direction of the steering wheel to follow the trailer.

The trailer hand valve, also called the trolley valve or Johnson bar, is used to work the trailer brakes. It should be used only to test the brakes.

If you need to back your trailer but cannot back up in a straight path, you should back on a curved path toward the driver's side of the vehicle. This will permit you the best possible visibility while backing.

When a vehicle goes around a corner, the rear wheels follow a different path than the front wheels. This is known as off-tracking, or "cheating."

Combination vehicles need more space on the road than other commercial vehicles because they are longer and need more space to turn and stop. It is especially important to properly manage space when you are operating a combination vehicle.

Before a trip, ensure that air in the air brake system reaches all trailers. Do this by waiting for air pressure to build, then sending air to both the emergency and service lines and opening the shut-off valves on the rear of the last trailer. If air escapes from the shut-off valves in the rear of the combination, the air is being supplied to the entire vehicle.