What commodity represents over 40% of the tonnage shipped on American freight trains?
Drag freight bulk shippers were used on the heavy freights in the 1990s. Because of coupling limits, only single units were used. Drag freight A drag freight is a slow, high-tonnage railroad train, often carrying commodities such as coal or ore. Compared to "fast freight" trains, drag freight trains have a very low power-to-weight ratio, making them somewhat unpredictable on steep grades or hilly routes. This causes many dispatchers to be extremely conservative with how they handle drag freights, especially when they share lines with higher priority fast freights and passenger trains. Before and during World War 1 and into the 20s
Rail freight transport trains are generally longer than passenger trains, with greater length improving efficiency. Maximum length varies widely by system."See" longest trains for train lengths in different countries. Generally trucking moves the most tonnage of all traffic in most large economies. Many countries are moving to increase speed and volume of rail freight in an attempt to win markets over or to relieve overburdened roads and/or speed up shipping in the age of online shopping. In Japan, trends towards adding rail freight shipping are more due to availability of workers rather than other concerns. Rail freight tonnage as a percent of total