Lights on a moving vehicle

[peter burton]

I have always been led to believe that reflective triangles fitted to the rear are strictly for trailers only, if nothing else just to let the following vehicle know that something beyond is pulling it with a draw bar. A triangle used stationary in the road as a warning is not classed as a vehicle obviously. Still, if cyclists can use flashing high-density rear (and front) lights that are so bright as to hurt the eyes with impunity why can't we use 'safety devices' to our advantage, as the chances of being stopped by 'the law' are practically non existant.
Peter.