I made a device that counts all trains that go past it. It can work with a single straight rail, or any type of intersection. Simply hover over a substation to view the count :)

Blueprints:

Train Counter (Single Straight Rail)
https://factorioprints.com/view/-MujR...
Train Counter (T-Intersection)
https://factorioprints.com/view/-MujR...
Train Counter (Roundabout)
https://factorioprints.com/view/-MujS...
Train Counter (Celtic Knot)
https://factorioprints.com/view/-MujS...

Patreon:
  / joshstpierre