- trunk:
- m7 bit 6: road present
- m7 bit 7: tram present
- nrt option 1:
- m4 bit 0..3, road subtype, 0xF = no road
- m4 bit 4..7, tram subtype, 0xF = no tram
- nrt option 2:
- m7 bit 6: road present
- m7 bit 7: tram present
- m4 bit 0..3: road subtype, only valid if m7 bit 6 is set
- m4 bit 4..7: tram subtype, only valid if m7 bit 7 is set