[Mr Muntarg]

For several years I have used 5mm I-R LED receivers under the track surface with matching emitters overhead. Very recently I spotted sideways-facing LEDs and have been successfully trialling those as they fit nicely under the track surface (Policar). The receivers work well with white LEDs overhead so that will make life a bit easier when using temporary layouts and free-standing light-bridge. 

Leo

Ebay Linky:    https://www.ebay.co.uk/itm/225484518933

My proof of concept set up in Scalextric START track.

That's a nice neat solution . I have seen a few option for under track . I was bit worried about reliability especially with different colored guides. Be interested to see how you finding it . I assume this is essentially how the Arc Scalextric system is but i haven't investigated it. I found that wont read white pickup at all and is hit and miss on a few black ones .