As a continuation of Cities in Motion series, Cities: Skylines acquires players to plan plenty of public transport lines to assist city development meanwhile the line map could be a mess. Here are some my personal transport line numbering rules and planning principles which are helpful for me to manage my city public transport.

This guide provides 2 different versions of line numbering systems that are partly same. The full version uses letters B, C, F, L, M, N, P, R, S, T to indicate transit ways and may be suitable for complex transport network in large cities. On the contrary for small cities, the simplified version removed letters L, M, N, S and introduced more numbers to make it more realistic. But notice please, the rules are simply designed to serve for the city creation, if there are some situations would be better to break rules, so break them. In addition, some planning suggestions are also here for your reference. Convinced that these concepts would be useful and significant even in coming CSL2, to read those now might be not too late yet.