Maryland CDL DMV Endorsement Double 1

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.

Retarders are mechanisms in some vehicles that help slow a vehicle and reduce the need for braking. The four basic types of retarders are exhaust, engine, hydraulic, and electric.

If a pre-trip inspection reveals a load to be oversize, the driver must confirm that all required signs, flags, lamps, and reflectors are safely and properly mounted, and that and all required permits are in their possession.

For your own safety, when placing reflective warning triangles, you should carry them between your body and the oncoming traffic.

Some older vehicles with air brakes have front brake limiting valves. These valves were intended to reduce the risk of front wheels skidding. However, research has shown that such devices are unnecessary, so they should be left in the "normal" position.

Tractors, trucks, and buses with Anti-Lock Braking Systems (ABS) have yellow malfunction lamps located on their instrument panels. Trailers have yellow ABS malfunction lamps on their left side, either on the front or rear corner.

Vehicles with trailers are vulnerable to rollover due to the "crack-the-whip" effect, which is caused by rearward amplification. Rearward amplification varies from vehicle to vehicle, so it is important that drivers are aware of the rearward amplification of their specific vehicles.

The right lanes of a roadway are generally intended for vehicles traveling more slowly than surrounding traffic. If being slowed down by a heavy load, you should stay in the right lane.

When inspecting your tires, verify that there is tread depth of at least 4/32 of an inch in every major groove on the front tires and tread depth of at least 2/32 of an inch in grooves on the other tires. Be sure that your tires are not too worn, are not cracked, have proper air pressure, and are all equally sized.

If confronted by an aggressive driver, it is most important to get out of their way. Avoid making eye contact and do not gesture at them. Report them to the appropriate authorities once you can safely do so.

Any foreign object on the road is potentially dangerous. For example, something seemingly harmless, such as a cardboard box or paper sack, could contain a hard or heavy object that could do serious damage to a vehicle.

When backing a straight truck, you would turn the wheel in the direction you want to go. By contrast, when backing a vehicle with a trailer, you must turn the steering wheel in the direction opposite of where you want to go. Once your trailer starts to turn, you should turn the steering wheel the other way to follow the trailer.

The trailer hand valve should not be used for parking. This could cause all of the air to leak out of the braking system, resulting in the brakes releasing. Instead, use the parking brake.

A large vehicle requires more space when entering or crossing traffic than a smaller vehicle. This is not only because the vehicle itself is larger, but also because it needs a longer distance to accelerate.

In double and triple combinations, the trailer farthest from the tractor is the most vulnerable to rollover.

Factors that can affect stopping distance include your vehicle's speed, its weight, and how slippery the road surface is.

An alcohol evaporator can help prevent ice from building up in an air brake system. In cold weather, the evaporator should be checked and refilled every day.

An Anti-Lock Braking System (ABS) is in place as an addition to a braking system. It intervenes to prevent brakes from locking up during hard braking. If ABS is not working, the basic braking functions on a vehicle will still remain, so the driver can continue to drive and brake normally.

To warn drivers behind you that you are about to slow down, it may be a good idea to first lightly tap your brake pedal a few times to make the brake lights flash.

If you begin to feel drowsy while driving, the only safe response is to safely leave the road and get some sleep. Using artificial stimulants can be dangerous because they may cause extreme fatigue when they begin to wear off.