To handle increased weights allowable under axle weight loading, many trucking operations have gone to the "train" or "pup-train" vehicle combination. In this type of combination, another trailer is pulled behind the regular tractor-trailer by means of a "converter dolly."
Drivers on train operation will discover that new skills are required for safe operation as well as an understanding of the equipment operation and hook-up. More than ever, you must be ready to adjust for changing conditions well ahead of time in order to take defensive or appropriate action to avoid trouble.
Power should always be applied when pulling on a straight stretch while underway (a steady pull, as opposed to intermittent application and reduction of power) with a small amount of reserve power always available. In the event that the rear trailer starts to fishtail or whip, apply trailer brakes lightly and increase power.
Drivers in "train" operations, as well as those driving semi trailers, should avoid sudden lane changes or turns and speeds too fast for conditions as these actions can result in severe whipping or possible jackknife situations.
Regular vehicle checks should be made of the complete unit, paying particular attention to the hook-up of the rear trailer, including:
- the hitch on the rear of the lead trailer
- the safety catch on the hook
- the safety chains or cables
- airlines between the trailers are secured and not allowed to sag down too low
Hooking up a "train" or "pup-train"
- Park the rear trailer and set trailer brakes.
- Position the dolly converter in front of the rear trailer so that it is in line with the kingpin.
- Hook up the tractor and lead trailer.
- Back the tractor and lead trailer in line with and up to the converter dolly.
- Before hooking up to the converter, a thorough trailer hitch inspection should be made. Watch for cracks or breaks in the weld, loose bolts, weak lock springs and bent or distorted cross-members where the trailer hook is attached.
- Hook and secure the converter dolly tongue to the pintle hook by hand. Fasten safety latch and chain. Ensure that the safety pin is fastened (if so equipped). This is extremely important! This action will ensure the high degree of safety the trucking industry main tains, not only for themselves, but for other users of highways as well. "Train-drivers" should make a point of checking the safety latch on the trailer hitch each time they stop for a vehicle check.
- Safety chains and cables should be inspected before being attached. When fastened to the lead trailer, they should be crossed so that if the converter dolly tongue breaks loose, it will be held suspended off the roadway while the driver attempts a safe stop.
- Connect the air hoses between the two units, ensuring that all air lines, especially on the converter dolly, are well secured and not sagging too low.
Some companies that operate equipment with brakes on the converter dollies have applied coloured tape to the air lines in order to identify the service and emergency lines, thereby eliminating the ossibility of improper hook-up.