tim-b wrote: where does the 240/minute come from? ...
The explanation is here, in this extract from the govt guide to bike lights
Purely flashing lights are not required to conform to BS61023, but the flash rate must be between 60 and 240 equal flashes per minute (1 to 4 per second) and the luminous intensity must be at least 4 candela. (This should be advised by the manufacturer).
https://www.gov.uk/government/publicati ... s-lighting
AIUI, the point is that the lighting regs require all vehicle lights to be steady lights and flashing lights on pedal cycles are an exception to that rule ie they must comply with this flash rate. In my earlier post I should also have mentioned that the rate has to be "equal."