The Red & White fleet numbering system which became a distinctive feature of the company in the post-WW2 era, was introduced around the time of the sale to the BTC, and applied retrospectively to older vehicles. It did not apply to sister companies in the group, such as United Welsh.
The system seems to perplex some people, and Roger Davies referred to it as ‘batty’ in one of his books. That’s a little unfair, as each fleet number conveys useful information about the vehicle, although the use of classifications was a little arbitrary in some respects. However, I’m sure the UD871 is more revealing about the vehicle than 1508. Its downfall, perhaps, was that early generation computers had problems listing the vehicles in a logical order. I am not aware of any imitators in the UK, at least in the period when R&W used it, although I have come across similar systems in Germany – for example, the municipal operators in Bonn and Darmstadt have the 2 digit year number as the first two digits of a four digit fleet number. In Bonn, buses were numbered yy01 upwards, and trams/U-Bahn cars yy51 upwards.
The R&W system used a type classification letter or letters, which conveyed information about the type, size and type of seating, as the first part of the number. The detail of the classifications varied, for example ‘L’ was used for lowheight double deckers, regardless of length and seating capacity, while ‘R’ indicated a 36′ (long) RE bus, with ‘RS’ for shorter RESL types with, in practice just 6 or 7 less seats.
The numeric portion of the fleet number, sometimes separated from the type classification with a dot, consisted of three or four digits, of which the last two indicated the year the vehicle went into service (or in some cases, the year built). The first one or two digits simply followed a numerical sequence through the batch, so that the first 9 vehicles had three digit numbers, and the tenth and all subsequent vehicles had four digit numbers. Thus, RC969 (registered SAX9G – the 9th RE Coach of the 1969 batch) was followed by RC1069 (SAX10G). Entirely logical, really.
One issue was that there could be several buses with identical numeric portions. R&W managed this in 1971 with four vehicles with ‘171’ as the numeric portion. When the fleet was combined with that of Western Welsh, that went up to 8, which was presumably too much for the rudimentary computers of the day! Thus the fleet was renumbered so that the numeric portions were unique, with the largest batch of each year taking the lowest numbers.