A project that i was developing for a workshop about electronics is a LEGO® train controled by an arduino. The project it’s explained in here. There were two situations where it was necessary to detect the train’s position. When this is was arriving to the station and when is was on an external track. First i’ve tried to use “Line Tracking” sensors but didn’t have enough range. On the second try used a Keyes IR Obstacle Sensor (this model) and they worked.