[skidlids]

I have been sent the following wording so that I can incorporate it in the Technical Regulations (Rule books)
This is how the ACU have worded it so it should be standard across all Classes/series

Rain Light
All motorcycles must have a functioning red light mounted at the rear of the machine to be used in rain or low visibility conditions as instructed by Race Control. The team or rider must ensure that the light is switched on whenever a rain tyre is fitted on the motorcycle and/or when any practice or race is declared “wet” by Race Control.
Lights must comply with the following:
a) lighting direction must be parallel to the machine centre line (motorcycle running direction), and clearly visible from the rear at least 15 degrees to both left and right sides of the machine centre line.
b) mounted on the seat/rear bodywork approximately on the machine centre line, in a position approved by the Chief Technical Officer. In case of dispute over the mounting position or visibility, the decision of the Chief Technical Officer will be final.
c) power output/luminosity equivalent to approximately: 10 – 15W (incandescent) 0.6 – 1.8 W (LED).
d) the switch must be accessible.
e) rain light power supply may be separated from the motorcycle main wiring and battery.