Intermodal; trailer and container sizes

Just something I never really considered...

The intent of this topic is to discuss how increased trailer and container dimensions have impacted the railroads, and their handling of TOFC/COFC; know nowadays as Intermodal. This topic is meant to be somewhat broad, but directly relating to how railroads addressed the changing length, width, and height of intermodal vehicles over time. It may be interesting to hear how intermodal has developed with regards to the physical dimensions of the trailers and containers in use today. Seeing the wide variety of trailers and containers in today's trains makes some wonder just how the railroads dealt with having the required equipment to handle everything from 20' containers to 53' trailers.

If I remember correctly, the US Government first addressed the weight/length limit of trucks in 1956; during the planning stages of the Interstate Highway System. I believe during this time the maximum dimensions of trailers was 40 feet long, 8 feet wide.

Then in 1975, trailers were permitted to grow to 45 feet.

Again in 1982, trailers grew to 48 feet, 8'6" wide.

I don't know when 53' trailers were permitted nationally.

Containers. I know virtually nothing about the dimensions of them. I realize they "followed" the trailers' increase in size here in the US, but was curious as to any global considerations that may have impacted (or impeded) their increase in physical size. Also of interest is the use of "standard height" and "hi cube" containers. It would be interesting to read how intermodal containers came about; and how they undoubtedly "grew" in size into today's common sizes.

In addition, it would be interesting to discuss how the North American railroads addressed these size increases; which required additional investment in newer, larger rail cars to carry these ever-growing shipments.

As a starter question for this topic, does anyone know the history behind international containers; what were the permitted dimensions and when?

Rob, to your "starter" question, I would highly recommend reading "The Box" by Marc Levinson and "Box Boats" by Brian Cudahy... I've read the former but not the latter. From those that read both, Levinson's is the one to pick.

Just a quick reply before work , but i believe the original ISO container size was 20 ft * 8ft *8ft . ( interestingly , i 'm not sure if it was specified as a metric measurement or imperial , but has always been known as a 20 ft container ) . this is the measurements a TEU is based on .

The many voices (some accurate, some not) of Wikipedia have a few things to say on the issue:
http://en.wikipedia.org/wiki/Containerization

interesting article , in my quick skim read of it , i saw no mention of twistlocks . fascinating things , the standards and location pertaining to these are probably more important than the actual size of the container . I only recently found out how they worked . I always wondered how they locked and unlocked them in a stack of containers , 5 or 6 containers high .

Off to a good start!

Thanks for the "required reading" suggestions. I never came across the "Containerization" entry in Wikipedia before; somehow I missed it.

So, Mr Benton, just how do they use (reach?) the twistlocks when they're stacked 6 high on a ship?

Rob, I think 45's actually came out under dereg in 1980, no? The 53s were introduced in 1991. To your point, the rail industry has been in a game of catch-up for quite some time, due to the migration to larger trailer sizes and the growing popularity of using containers vs. trailers for intermodal moves. The root of the issue is equipment longevity: A truck trailer/container has a life of 10-15 years. After that time, they might have some life left in them, but they're fully depreciated and pretty beaten. The industry can, therefore, cycle out of service an obsolete size/spec in a relatively short period of time. Case in point: 48' intermodal trailers/domestic containers are now relatively rare. In contrast, rail equipment designed for 48s, with its 50-60-yr life, can't be cycled out nearly as quickly due to cost and depreciation issues.

Hi folks,

Intermodal has a host of interesting questions which can be worked through; everything from the containers themselves, to their flat/well cars, to the support equipment, to port operations.

With that, Robert Paniagua, one of the Moderators at General Operations, and I agree we can get the best traffic in his Forum. So, I'm sending it there, with a shortcut here at Locomotives, Rolling Stock, and Equipment.

BTW, a few years ago I saw one of Union Pacific's custom-built container flats ... they were cut down in 1967 from Common Standard era baggage, postal, postal-storage, and horse-express cars. I last saw it at Heritage Park in Council Bluffs, holding a potable water container. Its six-wheel Commonwealth trucks were still part of what it was

SooLineRob wrote: So, Mr Benton, just how do they use (reach?) the twistlocks when they're stacked 6 high on a ship?

Well as i read it (possiby on here or a link from here ) , is that the automatic twistlock is a spring loaded mechanisim. When a conatiner is loaded on top of them , it springs into the closed position , holding the container in place . all good but if it wasnt automatic release , then somehow the mechanisim would have to be opened . pretty tall order ( excuse the pun ) on a double stack , let alone a stack 6 - 8 containers high .
So the spring is strrong enough to hold the twsit lock in position , i presume it has been calculated to be strong enough to withstand normal sideways sawy etc on a ship or vechicle . to lift the container off the stack , the lifting crane or whatever has to exert an upward force greater than the actual force required to lift the container . once the upward force reaches the required upward pressure , the twislock twists into the release position , and the container is freed from the one underneath it .
What is unclear to me is how they determine which containers / equipment has to have auto twistlocks . that seems to be quite a job in itself .

Cowford wrote:Rob, I think 45's actually came out under dereg in 1980, no? The 53s were introduced in 1991.

Hi Cowford,

I got the dates for 45's and 48's here:

http://www.fhwa.dot.gov/reports/tswstud ... apter3.pdf

and here:

http://ops.fhwa.dot.gov/freight/publica ... final_rpt/

Thanks for the 53' info. Very interesting to consider the service life of "highway" vehicles versus rail equipment. I seem to recall a flat car of 75' being used for early TOFC; which made me curious as to why the railroads chose that length for a TOFC rail car if 40' was the nominal length of the trailer. If I remember correctly, the ATSF was the first railroad to operate "spine cars" in a 10 trailer configuration. I'd be curious to know if they were configured to handle 10 45' or 10 48' trailers and containers. I also recall seeing all those "cut down boxcars" in the mid-to-late 1980's being used for single 48' trailers.

Another element to your point that made me wonder "what the heck happened to all those early double-stack 5-pack well cars with the bulkheads" for 40' containers? It seems the equipment manufacturers were confident on the containers remaining that size for some time. Then all of a sudden Inter-Box Connectors showed up, allowing "Twin 20's", 40', 45', and 48' conatiners to be stacked randomly, rendering the "bulkhead" well cars obsolete rather quickly.

I've found very little "history" on container sizes online, which makes me speculate there was some international/global considerations for limiting containers to 40' for some time after the U.S.A. allowed 48' trailers and containers for domestic use. Which no doubt complicated the rail car manufacturers' product catalogue...

John_Perkowski wrote: BTW, a few years ago I saw one of Union Pacific's custom-built container flats ... they were cut down in 1967 from Common Standard era baggage, postal, postal-storage, and horse-express cars. I last saw it at Heritage Park in Council Bluffs, holding a potable water container. Its six-wheel Commonwealth trucks were still part of what it was

Now that would be an interesting "thing" to see!

for international trade , i think its either 20 ft or 40 foot long , or it would not be considered as a container for stacking etc .
I know in NZ , the railway built 23 foot containers ( too fit a common railway flat car 46 foot long ) , but these were for domestic use only . i think the product most commonly carried(milk powder ) , got repacked into 40 ft iso containers at the port warehouse .

And think that 53 feet will remain the longest trailer for possible the rest of our time, because lengthening it tom 60 feet or even 57 feet would be too wide and won't take the turns not even on trains, although some flatcars can hold up to 80 feet, with two 33-35ft containers

Mr Benton,

Thanks for the info on Twistlocks. Interesting stuff. I also find it interesting NZ uses 23' domestic containers. As the USA uses 28' trailers (allowing a rail car to carry "Triple 28's or Twin 45's"), it really becomes clear how "complicated" intermodal can get in today's global economy.

Mr Paniagua,

While doing the preliminary research for this topic, I also wondered "what's next" with regards to trailers and containers. As 53's have become the norm, I wonder if/when some of the "grandfathered" trailer lengths allowed by individual USA states may become the next de facto "national standard"; 57'6" or 59'6". If I remember correctly, President Ford mentioned "fuel efficiency" in his decision to allow 45's in 1974. He imposed the 55MPH national speed limit, and giving consideration to the impact that would have on commerce, allowed larger trailers to carry more goods in order to offset any losses incurred by the lower speed limit. With today's drive for conserving natural resources, I wonder if the trucker's lobby will use "past practice" and seek an increase in trailer size in order to "move more with less".

Part of the limitations on international container size/weight is the allowances on other railways. We used to do 20' tank containers and some had to be loaded short to meet the weight limitations in the UK.

Domestic trailers over 56 feet won't become popular unless the current weight laws are changed. 48's & 56's are not filled unless the shipments cube out b/4 they reach the allowed max weight. Part of the drive to the 56' trailer was it's ability to spread out the 45,000# to make sure the unit wasn't over on axle weights under the Fedeal Bridge Formula. The domestic 48' & 56' cans were adopted by long haul companies because they utilize a 40' twistloc spacing and can be top lifted by regular intermodal lifting machines. The TOFC trailer these cans replaced needed special reinforcement and had to be lifted in exactly the right spot to avoid twisting and other structural damage. Plus TOFC sent the running gear down the rail while the domenstic COFC does not. Schneider National, J B Hunt, Hub Group are large enough to benefit from having 1,000 chassis for 2,000 boxes while a smaller carrier who cannot provide enough TOFC business to make it worthwhile. Fed Ex & UPS are the largest TOFC companies around, once again, due to the amount of long haul they can shift to the RR.