Development of Axle loadings in the US

I know this is strictly spoken not the correct forum, but couldn't find a separate cathegory for infrastructure - maybe an idea to add one?
Anyway - to the question: What is the "standard" (if there is any) axle loadings on US main- and branch lines today, and how has the development gone?

USRailFan wrote:I know this is strictly spoken not the correct forum, but couldn't find a separate cathegory for infrastructure - maybe an idea to add one?
Anyway - to the question: What is the "standard" (if there is any) axle loadings on US main- and branch lines today, and how has the development gone?

Well, I know there are maximum weight categories for (I believe 4 axle) freight cars in the US; current standard 263(,000 lbs = kips), new standard 286kips, and eventually 316kips (no time frame, if ever - but some of these 316 cars do exist) - the standard is currently moving toward 286kips, and this is in fact causing concern for shortlines in that they will need to upgrade track/bridges to handle those higher limits to retain customers. (Indeed there are loan and grant programs out there for just such upgrading). For a 286 4-axle car, it will be a 32.5t axle loading; however if the car was 6 axle (which is very rare for North American freight cars) then it's only 22t per axle. A 316 is 143t, while the newer Gevo and SD90s locomotives are roughly 195t; the 316 will have only 4 axles for a 35.75t/axle rating, while the Gevo has a 32.5t/axle rating - to a first approximation, the 316 freight car is heavier on the rail (axle-loading wise) than large 21st Century locomotives!

Edit: freight cars have progressed in weight over the centuries - there were weight standards such as 70t in the 1960s, and 100t by the late '60s (net - add 7-10 tons or so for tare weight: i.e. weight of the freight car itself). However not sure when 263 (120t) was made a standard. Heavier freight cars pre 1970s (such as 'pregant whale' tank cars or battleship coal cars) used 6 axles, but except for some speciality cars (like heavy duty/depressed flat cars) none do today.

Wouldn't it seem that if the new cars built for the heavier weights were equipped with 6 axle trucks it would be much less costly than replacing hundreds or thousands of miles of rail? I understand that it would add another pair of axles and add maintanence costs, but there is a lot of older rail in service that would require replacement, and I doubt that a lot of the shortlines and regionals would ever be able to afford it. Also, wouldn't a lot of bridges need to have capacity increased?

trainwayne1 wrote:Wouldn't it seem that if the new cars built for the heavier weights were equipped with 6 axle trucks it would be much less costly than replacing hundreds or thousands of miles of rail? I understand that it would add another pair of axles and add maintanence costs, but there is a lot of older rail in service that would require replacement, and I doubt that a lot of the shortlines and regionals would ever be able to afford it. Also, wouldn't a lot of bridges need to have capacity increased?

Apparently 3 axle trucks weren't ever seriously considered - the plan is 286Ks on 2 axle trucks or bust...

Here's an article on the topic from Railway Age, basically discussing how to deal with it.
http://www.railwayage.com/apr00/smallroadheavyload.html

Another article (not directly linkable) indicates that for the foreseeable future 315K cars are less economical than 286K, so the limit may stablize ('may' being the key)

Sir Ray....Thanks for the link...after reading and re-reading the article I can't say that I found any feasable answers....just more questions. When you add up the "ifs" and "buts" of the article you come up with a negitive number....they seem to contradict themselves several times, and then give a conclusion that seems to say we're not sure....there are too many variables that have to be answered on a specific, road by road basis to make a definate conclusion. The article kinda reminded me of a political speech where the speaker doesn't really want to make a commitment one way or the other about an issue to placate both sides.

I guess to summerize that and many other such articles:

The Class I railroads can handle the 286K cars in most cases, and can gain a 3+ % efficency (they may not gain such an advantage for 316K cars, and so there may not be the rush to that loading as there is for 286K).
Since the Class Is, and customers who deal with them, constitute the majority of new car purchases, new freight cars are being designed and built to the 286K limit.
There has been in the past significant antagonism by the Class I to shortlines and spun-off branchlines - this was certainly discussed by Railway Age during the mid-1990s (it included such things as Class I building transloads near shortlines to steal the shortline's tonnage). While this antagonism seems to have cooled alot, Class Is don't particularly worry if the shortlines cannot handle larger size cars - albiet there are various grants and loans out there to help the shortlines to improve their trackage. So, while this issue is not entirely clear-cut, it isn't a deep dark emigma.