I cannot praise the tramways in Bremen high enough - of the many European cities I have visited, this public transport system is up there with the best. The trams are efficient, fairly frequent and comfortable - meeting the needs to most travellers who simply need to go from point to point. There is a good number of lines which do reach most places of interest.
The ticketing system is also fairly intuitive, and what is more, the tram system connects the city airport to city center - simply a 15 minute trip (give or take time for tram to arrive).
Aside from frequency, I would say this can be compared against the transport systems in places like Tokyo or Hong Kong! read more