Flat wagons (sometimes flat beds, flats or rail flats, US: flatcars), as classified by the International Union of Railways (UIC), are railway goods wagons that have a flat, usually full-length, deck (or 2 decks on car transporters) and little or no superstructure. By contrast, open wagons have high side and end walls and covered goods wagons have a fixed roof and sides. Flat wagons are often designed for the transportation of goods that are not weather-sensitive. Some flat wagons are able to be covered completely by tarpaulins or hoods and are therefore suitable for the transport of weather-sensitive goods. Unlike a "goods wagon with opening roof", the loading area of a flat is entirely open and accessible once the cover is removed.
Flats form a large proportion of goods wagons; for example in 1998 they comprised 40% of the total goods fleet owned by the German carrier, DB, the overwhelming majority of which were flat wagons with bogies.
Typical goods transported by these railway wagons are: vehicles, engines, large pipes, metal beams, wire coils, wire mesh, half-finished steel products, (sheets, coils, pipes, bars and plates), containers, rails, sleepers and complete sections of railway track. Gravel, sand and other bulk goods are transported on flat wagons with side panels.
International UIC classification
Flat wagons are classified by the UIC into:
Ordinary goods wagons with category letters "K", "O" and "R", and
Special goods wagons with category letters "L" and "S".
The main difference between the ordinary and special types of flat wagon is that the former always have to have a flat deck that can be driven on, whereas the special types do not have to be so designed. Within both types of flat wagon, there are variants with separate axles as well as bogie wagons.
In addition numerous other terms are used to classify flat wagons according to their purpose, but without clear and comprehensive specifications.
UIC standard goods wagons
Attempts by the International Union of Railways (UIC) to standardise flat wagons go back to the 1950s. These efforts led to the establishment of characteristics for so-called "standard wagons". Standardised flat wagons are specified in the following UIC pamphlets:
UIC 571-1 – Standard wagons – ordinary two-axle wagons
UIC 571-2 – Standard wagons – ordinary bogie wagons
UIC 571-3 – Standard wagons – Special-purpose wagons
UIC 571-4 – Standard wagons – Wagons for combined transport
The implementation of these guidelines is partly binding and partly voluntary for members of the UIC. Since the end of 1977, flat wagons that partially conform to these guidelines are identified by the designation "UIC". Flat beds that comply fully with the leaflets, and are therefore true UIC standard wagons, are given the designation "UIS St".
K: Ordinary two-axle flat wagons
The Class K flats were originally one of the largest families of goods wagons, not least in Germany, thanks to the many older type stake wagons (stanchion wagons) that were assigned to it. The bulk of their work has since been taken over by special flat wagons. By 1998, DB only had 10,000 of this type left.
The majority of ordinary two-axle flat beds built since the 1950s were those with folding sides and short swivelling stanchions of UIC type 1 with, at least in Germany, an axle base of only 8 metres.
In recent years new K wagons have been developed. These have fixed ends and a tarpaulin cover and are therefore also suitable for hygroscopic goods. Their designation is Kils, based on the UIC classification of goods wagons.
In addition to the normal letters indicating length and weight (k, kk, n, m and mm) the Type K may also have the following index letters: b – with long (side-)stanchions (usually designed as insertable stanchions) i – with removable cover and non-removable ends (tarpaulin wagon) and l – without stanchions p – without sides (not used with i)
L: Special flat wagons with separate axles
Today this class contains: Three and four-axle car transporters (see below) with one or two decks, and Two-axle container wagons Only of historic significance, by contrast, are pod wagons (see below) and cradle wagons (see below). As a rule, L wagons do not have stanchions.
The most important index letters for basic classification of current types are: a – articulated wagon with 3 axles, aa – double wagon with 4 axles, d – fitted out for the transport of motor cars without deck, e – with decks for the transport of motor cars (double decker), g – fitted for the transport of containers (Container wagons).