Ticket validators (also sometimes called cancellers), into which the passenger has to insert their ticket to date stamp it either before or just after boarding the bus, train or tram, have never been in widespread use in the UK, unlike in mainland Europe where they are commonplace - mainly on suburban rail, light rail, bus and metro systems but also on long-distance trains in some countries such as France (where they are called "composteurs" on the SNCF national rail network) and Italy. Their purpose is to allow passengers to buy a ticket in advance of the day of travel (with some networks offering sets of, say, five or ten single journey tickets at a discount) and then validate them when they wish to use them, and to prevent passengers from reusing used but unmarked tickets that are still within their period of validity. The only places I know of in the UK where they have ever been used are Sheffield Supertram and the Docklands Light Railway. In both cases, validators were used for about the first year or two of operation but were then abandoned. Sheffield Supertram also got rid of ticket machines at stops at the same time and replaced them with on-board conductors. I think the DLR replaced them with a 60 or 90 minute time limit on all single journey tickets (i.e. they had to be used within a certain number of minutes of the time of issue). I also seem to recall that in about the mid-1990s First buses in Bristol had multi-journey cards that had to be validated for each journey using on-board validators. Does anyone know of any other transport networks in the UK that have ever used ticket validators? I'm talking about paper ticket validators, not smartcard validators.