Wagons with opening roof

The wagon with opening roof is a type of railway goods wagon that is, nowadays, defined and standardised by the International Union of Railways (UIC) as Class "T". They are a large category of rail vehicle, predominantly used for the transport of hygroscopic bulk commodities such as cement, plaster, lime, potash and grain.

To date, there are four different types of wagon with an opening roof (by way of example, the years refer to when they entered service with the German carrier, DB):

The overall design and use of these wagons is however governed far more by the configuration of their wagon floors and walls than the methods of loading and unloading. These features, which are also coded by index letters, form the basis of this article's structure.

The classic lidded wagon for the transport of hygroscopic bulk goods was only procured by railway authorities in relatively small batches in comparison with other types of goods wagon. They were used by on standard, as well as narrow gauge, railways (e.g. the Saxon narrow gauge railways). Their design was based closely on that of contemporary open wagons.

They were loaded from above and unloaded, like covered wagons, through the side doors. Because unloading involved a lot of manual work, alternatives were already being sought by the 1920s. In the 1950s the self-discharging wagon with roof (see below) completely ousted the lidded wagon from its original field of operations. The last large batch of lidded wagons was procured by the East German Deutsche Reichsbahn in 1958.

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