When was the Whyte notation introduced?
Whyte notation
In Britain, small diesel and petrol locomotives are usually classified in the same way as steam locomotives, e.g. 0-4-0, 0-6-0, 0-8-0. This may be followed by D for diesel or P for petrol, and another letter describing the transmission: E for electric, H hydraulic, M mechanical. Thus, 0-6-0DE denotes a six-wheel diesel locomotive with electric transmission. Where the axles are coupled by chains or shafts (rather than side rods) or are individually driven, the terms 4w, 6w or 8w are generally used. Thus, 4wPE indicates a four-wheel petrol locomotive with electric transmission. For large diesel locomotives the UIC classification is used.