text: I selected this central point for the whole metro and tram system:
  
  Some metro tracks are tagged with
  
    voltage=1500
    frequency=16,7
  
  other with
  
    voltage=1500
    frequency=0
  
  Some tram tracks are tagged with
  
    voltage=750
    frequency=16,7
  
  Is that correct?
  
  I think 16,7 Hz is definitely wrong. It should be 0 Hz for DC (has someone selected by accident the wrong value in JOSM?).
  
  And sources in the internet say that the Metro uses 1200 V DC.