For Intercity-Passenger Transport nearly the same:
Example: Woodbridge to Tow Loaw, my first train line, became 1-WB-TW, later on, when i connected a third city for it, Dinnington St. John it became 1-WB-TW-DSJ
After that, I just took the start and the end city of a line into the name, example Dinnington St. John to Bexhill-on-Sea became 3-DSJ-BOS, but in total this line connects 6 cities, DSJ is the starting city and BOS the ending city of the line.
If it is a line raw ressource -> industry -> city its called in my game for example:
If only a good transport corrisponding Goods-City or, a ressource transport to an industry near a city Ressource-City
If i have multiple lines transporting the same type of freigt to one Industry/city, the get numerized.
Goods-Downham Market 1
Goods-Downham Market 2
and so on.
For Public Transport within city I give it a line number, the ÖPNV-Prefix (In German ÖPNV means “Öffentlicher Personennahverkehr” or in einglish Public Transport) and the City name for example:
I don’t adapt the name towards if I use busses or tram.
And with all my line names, the numerization represents the order in which they were set up.