Texas CDL DMV Endorsement Double 2

Stopping distance is affected by a vehicle's speed. The faster you are driving, the longer your stopping distance will become.

If you aren't sure that you have space for your vehicle to safely fit underneath an overhead object, slow down and seek an alternate route if possible.

Some pre-1975 vehicles have a front brake limiting valve, which has "normal" and "slippery" settings. The idea behind these valves was to limit the air pressure available to the front brakes when driving on slippery surfaces, and thereby reduce the danger of a front-wheel skid. Studies have found that this is not actually a concern, so if your vehicle has a front brake limiting valve, leave it in the "normal" position.

You should never exceed the speed shown on a "Maximum Safe Speed" sign.

All trucks, truck tractors, and buses must be equipped with emergency brakes and parking brakes. These brakes must be held by mechanical force.

Backing a large CMV is always dangerous because you will not be able to see everything behind you. If you must back up, use a helper, if possible.

If you are approaching a traffic light that has been green for a long time, there is a good chance that it will turn yellow before you reach it. Start slowing down and be ready to stop.

A low air pressure warning signal is required in vehicles with air brakes. The warning light is usually red and may be accompanied by a buzzer.

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.

Before a trip, you should ensure that air reaches all air brakes on all trailers by opening up the rear emergency line and service line shut-off valves to listen for escaping air. Close both shut-off valves before beginning to drive.

Before inspecting the engine compartment, make sure that the parking brakes are on and/or the wheels are chocked. Check the engine compartment before entering the cab and starting the engine.

On combination vehicles with air brakes, the tractor protection valve keeps air in the tractor or truck brake system, should the trailer develop a bad leak or break away from the tractor.

Double and triple trailer combinations are more likely to turn over due to the "crack-the-whip" effect than are other combination vehicles. Drivers should be aware of the rearward amplification of their specific vehicles and steer accordingly.

For safest handling when driving a double or triple combination vehicle, the most heavily loaded semi-trailer should be placed in the first position behind the tractor. The lightest trailer should be placed in the rear position.

Before beginning a trip, it is important to check the brake drums during your walk-around inspection. It is unsafe to drive if any brake drum has a crack more than one half of the width of the friction area.

When coupling, make sure you couple matching glad hands. They are often color-coded to help drivers avoid mistakes. Typically, blue is used for service lines and red is used for emergency lines.

If the air pressure warning light or buzzer comes on while you are driving, you should immediately stop and safely park the vehicle. This warning signal indicates that there is a problem in the air brake system that needs to be fixed.

Black ice is a layer of ice that is thin and clear enough for the road to be visible through it. This makes the road look as if it is merely wet.

Doubles and triples need more space than other vehicles, both because they are longer than other vehicles and because their size and weight prevent them from turning or stopping suddenly. When driving a double or triple, always make sure you have enough space before entering traffic, crossing traffic, or changing lanes.

Release dolly brakes by opening the air tank petcock. If the dolly has spring brakes, use the dolly parking brake control.