What is an impedence or Wee-Z bond?
Wee-Z bonds are part of a signal system that sends information, authorization and speed commands between the track and Metrorail trains. Wee-Z bonds detect the presence of other trains and automatically transmit speed signals to a train as it passes over the Wee-Z bond, depending on the location and speed of other trains in the area. If one train enters a portion of track where another train has been detected to be in front of it, then the Wee-Z bond sends a signal that causes the following train to stop.
