The LEGO Train system has evolved through several distinct power and control eras since its introduction in 1966, while consistently maintaining the same track gauge for compatibility. The current system uses battery power and Bluetooth control.
Evolution of LEGO Train Power Systems
The different eras of LEGO trains are primarily defined by how they were powered and controlled.
System Compatibility
All LEGO trains, from the first sets in 1966 to today, run on the same nominal gauge (width) of 37.5 mm (based on 5-stud track centerlines). This means that rolling stock (wagons, carriages, etc.) from any era can be used on tracks from any other era. However, the power systems have different technical needs:
Battery-powered trains (4.5V, RC, Power Functions, Powered Up) can run on any plastic or metal track, as their power source is onboard.
Track-powered trains (12V and 9V) require the specific track with conductor rails to function. 9V motors, for instance, have metal wheels that pick up power directly from the rails.
Mixing Systems: With minor modifications or adapter cables, it is often possible to run older motors using newer power systems and vice versa, a popular practice among adult fans of LEGO trains (AFOLs).