Florida CDL Permit Test - Double

Combination vehicles are usually heavier and longer than single commercial vehicles. For these reasons, they usually require more driving skill than single commercial vehicles.

Always signal before a turn or lane change. Begin signaling well in advance of the movement and keep the signal on continuously during the turn. If it is not self-canceling, make sure to turn your signal off after your turn or lane change is complete.

Most heavy-duty vehicles use dual air brake systems, in which there are two separate braking systems operated by a single set of controls. Each system operates the brakes on different axles.

It is always important to have enough water and antifreeze in a vehicle's cooling system. Despite the name, antifreeze is beneficial to an engine even in hot weather.

To reduce the chances of becoming fatigued on a long trip, a driver should stop for a break at least once every two hours or 100 miles driven.

A vehicle's total stopping distance is made up of perception distance, reaction distance, brake lag distance, and braking distance. With all of these factors included, an air brake-equipped vehicle traveling at a speed of 55 mph under ideal driving conditions will need approximately 450 feet to come to a complete stop.

Landing gear, or trailer supports, should always be completely raised before a vehicle is driven. When uncoupling, landing gear should be lowered to make firm contact with the ground. If a trailer is loaded when it is being uncoupled, you should lower the landing gear and turn the crank a few additional times to remove some weight from the trailer.