Pulling Double/Triple Trailers

Take special care when pulling two or three trailers. There are more things that can go wrong, and doubles/triples are less stable than other commercial vehicles.

Prevent Trailer from Rolling Over

To prevent trailers from rolling over, you must steer gently and go slowly around corners, on ramps, off ramps, and curves. A safe speed on a curve for a straight truck, or a single trailer combination vehicle, may be too fast for a set of doubles or triples.

Beware of the Crack-the-Whip Effect

Doubles and triples are more likely to turn over than other combination vehicles because of the “crack-the-whip” effect. You must steer gently when pulling trailers. The last trailer in the combination is the most likely to turn over.

Inspect Completely

There are more critical parts to check when you have two or three trailers. Check them all.

Look Far Ahead

Doubles and triples must be driven very smoothly to avoid rollover or jackknife. Therefore, look far ahead so you can slow down or change lanes gradually as necessary.

Managing Space

Doubles and triples take up more space than other commercial vehicles. They are not only longer, but also need more space because they can not be turned or stopped quickly. Allow more following distance. Make sure you have large enough gaps before entering or crossing traffic. Be certain your sides are clear before changing lanes.

Adverse Conditions

Be more careful in adverse conditions. In bad weather, such as slippery conditions and mountain driving, you must be especially careful if you drive double and triple bottoms. You will have greater length and more dead axles to pull with your drive axles than other vehicles. There is more chance for skids and loss of traction – allow more following distance. Remember the “one-plus-one” second rule for following other vehicles. Allow one second for each 10 feet of your vehicle’s length. Plus, add one second when you travel 40 or more MPH. For example, a 100 foot long combination vehicle traveling at 35 MPH would need 10 seconds of following distance. At 45 MPH, the same vehicle would need 11 seconds.

On slippery roads, allow much more space than you need for ideal driving conditions. Do not use the engine brake or speed retarder on slippery roads. Their use can cause your vehicle to lose traction. Remember the one rule that is important to all skids: “Restore traction to the tire.”

Watch For Jackknifing

If your tractor’s drive wheels or trailer wheels lose traction, the vehicle may jackknife. When a set of trailer wheels goes into a skid, you may have a trailer jackknife. You must then restore traction to your tires.

Take Care When Changing Lanes

Besides steering gently, you must watch your mirrors closely when changing lanes. Check the mirrors after signaling the lane change, after starting the lane change, and while completing the lane change. Do not change lanes near on-ramps, off-ramps or intersections.

Brake Correctly

Because doubles and triples are longer and heavier, you must apply brakes correctly. On long downhills, remember to go slowly enough that fairly light use of the brakes will keep your speed from increasing. Never use only the trailer brakes to control your speed.

On curves, remember to slow to a safe speed before entering the curve, then accelerate slightly during the curve. When empty, remember bouncing may cause poor traction and wheel lockup. An empty truck takes longer to stop than a loaded truck. In emergency braking situations, use either the controlled or stab braking method to stop your vehicle. These methods will help you stop doubles or triples in a straight line and prevent jackknifing. Remember that speed increases your stopping distance. If your speed doubles, your stopping distance increases four times – it takes four times the distance to stop at 40 MPH than at 20 MPH.