The open hopper is a self-clearing car with sloped interior hopper bays and bottom discharge doors, but no roof enclosure. It is purpose-built for bulk commodities that do not require weather protection and are delivered by top-loading equipment such as rotary car dumpers or bottom-dump facilities. Coal hoppers traditionally carry 100-ton payloads and operate in unit trains of 100 or more cars. Aggregate hoppers are typically shorter and heavier-built to accept large rocks.
High-sided, 3-bay or 4-bay design optimized for high-volume unit train coal service from mine to power plant or export terminal.
Shorter, lower-cube, heavier-duty car designed for quarry products; often equipped with metal liners to resist abrasion from rock.
Fitted with rotary-end couplers so the car can be inverted 360 degrees in a rotary dumper without uncoupling from the train.
Open hoppers are the preferred equipment for high-tonnage coal and aggregate unit trains where rapid loading at a mine or quarry and rapid unloading at a dumper or tipple are required.