When I first got interested in trains as a kid during the 1980s, the TOPS numbering system seemed to be rather simple, and made a lot of sense.
So you had :
diesel locos: 01-69
DC electric locos 70-79
AC electric locos 80-89
Departmental: 97
Steam: 98 (Vale of Rheidol, when it was BR!)
BR ferries: 99 (not trains, obvs.)
DMUs: 100-199
DEMUs: 200-210
EMUs AC: 300-399
EMUs DC: 400-499 (ex-SR network)
EMUs DC: 500-508 (non-SR)
Departmental: 900s
But nowadays you have AC EMUs numbered in the 7xxs and 8xxs (what happened to the unused 3xx ??), and some diesels in the 70s (why no Class 61/62/63/64/65 etc.?).
For example, around east London, you have Bombardier Aventras numbered 345 and 710.
Anyway, I'm sure there's an explanation!
So you had :
diesel locos: 01-69
DC electric locos 70-79
AC electric locos 80-89
Departmental: 97
Steam: 98 (Vale of Rheidol, when it was BR!)
BR ferries: 99 (not trains, obvs.)
DMUs: 100-199
DEMUs: 200-210
EMUs AC: 300-399
EMUs DC: 400-499 (ex-SR network)
EMUs DC: 500-508 (non-SR)
Departmental: 900s
But nowadays you have AC EMUs numbered in the 7xxs and 8xxs (what happened to the unused 3xx ??), and some diesels in the 70s (why no Class 61/62/63/64/65 etc.?).
For example, around east London, you have Bombardier Aventras numbered 345 and 710.
Anyway, I'm sure there's an explanation!