The 74HC595 shift register provides 8 outputs from the use of only three digital pins on an Arduino. Multiple 74HC595 shift registers can be chained together, and still only consume three digital pins ...

There are many ways to use an Arduino on a model railroad. These tiny, inexpensive, programmable computers can perform functions such as controlling signals, routing turnouts, and running animations.

Using an Arduino and 74HC595 shift registers with JMRI and C/MRI to control signal lights on a model railroad.. - fouldsy/arduino-jmri-cmri-signal-control ...