Originally Posted By: Silk
Not unusual then, but are today. The best photos I could find are models, and he's really nailed them. I worked on these in the mid '70's, and Doug Hillary had some involement with the company too. We called them doubles, but with the advent of the B Train (most common rig on NZ roads) they are called an A Train, and are now very rare...not considered safe apparently. The trailers were interchangable, they could be a semi or a full trailer, and went around the country dropping off and picking up trailers where needed. We had to reverse them out of the workshop, first time I got in one, I just reversed out of the shop and parked it in the yard. When I got back the foreman asked if I'd driven them before. From then on it wasn't so easy.
We run them in Canada (A, B and C trains). Maximum Canada-wide transport trailer length is 53 feet and combinations can be up to 82 feet; there is also a category 1A Tridem (3-trailer) Canada-wide which is longer still. And then there are also Provincial regulations for non interprovincial/international trains which are longer than Canada-wide, and there are special interprovincials for two adjacent provinces. Canada also allows a comparatively long tractor wheelbase for domestic operation, they can't travel through the US or Mexico (with a trailer attached).
There is no Federal weight limit but the tractor and first trailer must weigh more than the second or third trailer. In practice however all Provinces have weight limits based on the road type and construction.
It's just a natural reflection of long distances and typical product distribution practices (East-West on the mainland is 3,000 miles; Toronto-Vancouver is a common long distance run, for example most Japanese automobiles from port to largest market, of 2100 miles, similarly to Montreal it's 2300 miles).