At first glance, aggregates — stone, sand, and gravel — are unlikely darlings among railroad commodities.
They’re low-value and they tend to move only short distances.
But even though their revenue per car is low, they are nearly perfect freight: indestructible and relatively harmless if spilled.
In fact, stones and sand not only make money but they make enough to contribute to maintaining railroads’ track and structures.
Aggregates are found in every state from Florida to Alaska and every Canadian province from Nova Scotia to British Columbia.
So when stone and sand move by rail, they typically move short distances, generally fewer than 300 miles.
Most crushed stone and gravel move in trainload lots, but these are not like the unit trains that move coal from Powder River Basin mines to electric generating stations.
Rock trains often require switching at origin or destination because of track configuration, or the fact that a single trainload may represent shipments for two or more distribution yards, or because customer volume requirements vary from day to day.
Loading and unloading are typically slower, because of the loading equipment used and because cars in aggregates service are not equipped for rapid discharge.
Aggregates often move in gondola cars, which are unloaded from the top using backhoes or other heavy equipment.
Depending on the specific rock moved and the availability of freight cars, aggregates can move in specially designed hoppers often called “Ortner” cars, they can also move in two-, three-, and four-bay hoppers, and side-dump gondolas.
Rock often maxes out the weight limit on a freight car before it fills the inside.
Big railroads prefer to focus on the line-haul, not switching at terminals.
That’s one key element in keeping costs down.
The result is that customers make their own investments in track that can accommodate a trainload and allow efficient movement to and from a Class I railroad’s main line.
Unglamorous and often dirty, watch for these heavy haulers at off-peak times and in parts of the country where construction projects are constant.
On a line with even a moderate grade, these trains will reward you a heavy diesel growl.
This video was originally published by Trains as part of the Heavy Hauls DVD.
