Make sure air and electrical lines are not tangled, pinched, dragging against tractor parts, and have enough slack for turns.

Be very careful about driving bobtail tractors or tractors without semitrailers. Tests have shown that bobtails can be very hard to stop smoothly and can take longer to stop than a tractor-semitrailer loaded to maximum gross weight.

Go under trailer and investigate the back of the fifth wheel. Make sure the fifth wheel jaws have closed around the shank of the kingpin.

One good rule says you need at least one second for each 10 feet of vehicle length at speeds below 40 mph. At greater speeds, you must add 1 second for safety.

The emergency line, also called the supply line, has two purposes. First, it supplies air to the trailer air tanks. Second, the emergency line controls the emergency brakes on combination vehicles.

Put the tractor directly in front of the trailer. Never back under the trailer at an angle because you might push the trailer sideways and break the landing gear.

Emergency lines are often coded with red (red hose, red couplers, or other parts) to keep from getting them mixed up with the blue service line.

’t take a chance on getting hung up halfway across.

After the landing gear makes firm contact with the ground, turn crank in low gear a few extra turns. This will lift some weight off the tractor making it easier to unlatch fifth wheel, and to recouple to the trailer.

When connecting the glad hands, press the two seals together with the couplers at a 90-degree angle to each other.

If the air pressure falls more than the specified psi in one minute for combination vehicles, the air loss rate is too much. Check for air leaks and fix before driving the vehicle. Otherwise, you could lose your brakes while driving.

Triples have a rearward amplification of 3.5. This means you can roll the last trailer of triples 3.5 times as easily as a five-axle tractor. While the rearward amplification of a double is around 2.

There are more things to inspect on a combination vehicle than on a bus or straight truck. First, of course, there is the entire coupling system: the kingpin, the fifth wheel, etc. Next, there is the landing gear of each trailer. Not to mention a few more axels to check.

When only the trailer has ABS, the trailer is less likely to swing out, but if you lose steering control or start a tractor jackknife, let up on the brakes if you can safely do so until you regain control.

Check that the safety latch is in position over locking lever. On some fifth wheels the catch must be put in place by hand.

To legally pull a trailer with a GVWR exceeding 10,000 pounds, you'll need a Class A CDL. To pull triples, the doubles/triples endorsement on your CDL is also required.

’t take a chance on getting hung up halfway across.

’s specification usually 20 – 45 psi. This will cause the spring brakes to come on.

One good rule says you need at least one second for each 10 feet of vehicle length at speeds below 40 mph. At greater speeds, you must add 1 second for safety.

If the air pressure falls more than the specified psi in one minute for combination vehicles, the air loss rate is too much. Check for air leaks and fix before driving the vehicle. Otherwise, you could lose your brakes while driving.

Rear wheel braking skids occur when the rear drive wheels lock. Because locked wheels have less traction than rolling wheels, the rear wheels usually slide sideways to "catch up" with the front wheels. With vehicles towing trailers, a drive-wheel skid can let the trailer push the towing vehicle sideways, causing a sudden jackknife.

The heavier the vehicle, the more work the brakes must do to stop it, and the more heat they absorb. But the brakes, tires, springs, and shock absorbers on heavy vehicles are designed to work best when the vehicle is fully loaded. Empty trucks require greater stopping distances because an empty vehicle has less traction.

Make sure air and electrical lines are not tangled, pinched, dragging against tractor parts, and have enough slack for turns.

Trailers that do not have spring brakes have emergency brakes, which work from the air stored in the trailer air tank. A major leak in the emergency line will cause the tractor protection valve to close and the trailer emergency brakes to come on, but the brakes will hold only if there is air pressure in the trailer air tank. Eventually, the air will leak away and then there will be no brakes. Therefore, it is very important for safety that you use wheel chocks when you park trailers without spring brakes.

To unlock the fifth-wheel pull the release handle to "open" position.