Billund Legoland car controls
From an unofficial Legoland Windsor fan site 'Completely LEGOLAND Windsor'.


  Road Vehicles
  
  The cars, lorries and buses all appear to move and steer on their own,
  never leaving their set paths, yet not using any rails. How on Earth
  do they manage that? Beneath these paths are cables that emit a
  low-level radio wave specific to each vehicle - the vehicle picks up
  this signal, and uses it to steer. When the vehicle reaches one of the
  charging points dotted around it's track, it stops. One of the
  computers registers this, and a timer is started. When the timer
  reaches zero, the power to the charger is cut, and this signals the
  vehicle to continue along it's path. Outside park opening hours, the
  vehicles stop on the charging points and recharge fully overnight.
  
  Trains
  
  The trains work in a similar fashion to the road vehicles, but follow
  tracks instead of radio signals. When a train approaches a station,
  the train passes over 'slow down bars', which tell the onboard
  microprocessor to slow the motor. When it reaches a charging point,
  one of which is located at each station, a signal is sent to the
  control room, at which point a timer is started both in the control
  centre and in the train's microprocessor. Unlike the road vehicles,
  which can only go forward at a certain speed, the trains can go
  forwards, backwards, and vary their speed.
  
  Boats
  
  The boats are attached to rubber loops, which can clearly be seen
  under the water. These are driven by motors controlled by the
  computers in the control centre. A piece of metal on the hull of the
  boat allow sensors along the boat's track to detect the boat, and let
  the computer know where the boat is. The computer then uses this
  information to initiate various sequences, such as raising bridges, or
  opening and closing locks and powering water pumps.