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.