Hi,
I would like to design an ambient lighting for a staircase. I'm even thinking of using it as a main lighting.

(This is only an illustrative picture of a staircase)
There will be digital LED strips built in handrail. As a man goes along the handrail, the LED strip should light on, the light should move with the man.
The question is what sensors to use to detect position of a man to turn on corresponding part of a LED strip? The sensors can be built in handrail, they can be also on walls, whatever. PIR, some proximity sensors, ghz radar?