Ive been asked about the safety factors when towing doubles or even triples on a rare occasion.
I tow a 5th wheel, and tow behind that another vehicle or a pup trailer and sometimes even both.
Some state offices in Licensing don't mention a required Federal law,, requiring the second towed trailer or vehicle must have safety chains or cable to main tow vehicle. We all know about securing safety chains after hitching up,, But when you tow doubles, ( in my case, the 5th wheel and the other truck or pup trailer). You will need safety chains or cables to the main tow vehicle,, NOT just to the Trailer hitch of the trailer/receiver.
I accomplished the task of securing the second tow vehicle/ pup trailer to the main tow vehicle by using high tensil stregnth steel cable run underneath the 5th wheel to the tow vehicle. Now your probably wondering,, won't the cables hang low and drag the ground,, or be to tight,,etc.? I ran open EYE hooks,,, the type that are not a full circle eye hook, but slightly open. I lay out 2 cables, down each side of the main trailer inside the frame up over the trailer axles. I then lift the cables up over the eye hooks to keep them high but running along the frame to the front of the trailer and guide them both to a V meeting together at the front.Into a large EYE hook,, with a screen door spring to keep tension on the cables. I connect the cables to the Rear receiver on the tow vehicle and attach the cables to the Towed vehicle or pup trailer.. I use a spring on the towed vehicles cables to keep them up from dragging the ground with enough slack for turning. I use those Threaded chain Links to make the connections.
The point of this set up, is If the towed vehicle or pup trailer breaks free, its LEGALLY secured to the main tow vehicle.
Added note,,, When I do tow,, whether,single, doubles or triples,, I have back up/security cameras to view them while traveling, to watch how they track,, the tires and surrounding traffic which makes it easy to watch that little Prius sneaking up along side ya in that dreaded blind spot.
Its not a widely enforced law,, But if you get pulled over with doubles,, more then likely, The department of transportation officer will know the law/rules and more then likely ticket you for unsafe connections of cargo.
Be safe, and happy motoring, happy travels. And when towing Singles or doubles,,,,, 55 is the safest speed,, let the leadfoots race by in the passing lane,,,,,,, You will get there safe and sound.