The tntermodal market and equipment shifted so rapidly that new (and expensive) railroad equipment became obsolete within a few years.

As I understand it - The standard marine box was originally 8'x 8' in 20 or 40 foot lengths, though there were some shorter ones. Likewise the longest standard semi trailer was 40', but I don't remember how short the pup trailers were to allow doubles. This was because there was an overall length limit - when was the last time you saw a new cab-over semi tractor?

I'm not sure whether it was the US trucking industry or marine container services (or maybe both), but truck trailer and container lengths soon expanded to 45', then 48', then to 53' - with an increase in width to 8-1/2' and an increase in height also. This is also when pup trailers got to 28' and triples started showing up in some states.

The railroads (TTX especially) had to reposition the stands on TOFC flats, and they were just able to squeeze two 45' trailers on a car as long as they didn't have nose refers. When trailers went to 53', this idea didn't work either and some cars were drawbarred in pairs to carry three trailers, with the middle trailer spanning the two cars.

There was also a change in how trailers were handled for TOFC. "Circus ramps" were phased out in short order and TOFC is now only handled at large hubs with overhead handling to load nad unload. I read a report that the trucking radius for intermodal is considered 500 miles or less - and the remaining railroad intermodal operations seem to support this.

Based on my observations - marine still uses the 20' and 40 containers, and apparently some 45' - not sure about max width and height. The 48' capacity cars are now the bastard child that are of little use, and I believe some of these have been either shortened or lengthened. The import container terminals like the 40-45' cars because that is all they use, and they can usually load 45' containers in the top of 40' wells. They can load 48' and 53' wells with shorter containers, but you can fit fewer wells in the same track.

On UP's line across northern Oregon - it is rare to see any TOFC or spine cars, but there are plenty of stacks. And not all 53' containers are domestic products - since many companies are trucking and unloading the marine boxes at warehouses in the dock region, and reconsolidating them to 53' containers and trucking them to the nearest intermodal hub.

I may have some of this wrong. I did see Schnitzer in Portland a couple years ago cutting up TTX spine cars that could handle either trailers or containers - even though the cars were far from the end of their serviceable life. Railroad cars can now be in service for 50 years, but the business they are designed to carry only lasts 10 or 20 before something new and different comes along. Makes you wonder why the railroads fight so hard for such a small profit margin? I would guess most of the 70 ton cars and many of the 263k cars are now just as endangered.