Lights

In the UK, the regulations governing bicycle lights are set out in the Road Vehicles Lighting Regulations 1989[4] and their subsequent amendments, summarized in the Highway Code.[5] The regulations require a white front light, a red rear light, a red rear reflector, and amber/yellow pedal reflectors on the front and rear of both pedals. Reflectors must conform to BS 6102/2 or an equivalent European standard. The situation for lights is more complicated:
a light with a steady mode is considered approved only if it conforms to BS 6102/3 or an equivalent European standard;
a light without a steady mode is considered approved only if it flashes at a constant rate of between 60 to 240 flashes per minute and has a luminous intensity of at least 4 candela;
The majority of LED lights available are not approved for UK use since they have steady modes that do not conform to BS 6102/3. It is, however, legal to fit additional lights providing that they are of the correct colour, they do not dazzle other road users and that if they flash, they do so at a constant rate of between 60 and 240 flashes per minute.
National cyclists' organisations such as LAB (US) or CTC (UK)[6] are a source of lighting information.

Dunno how representative that is, maybe they can fine you. I think I recall hearing that any level of luminosity/flashing is permitted on cyclists, as long as there are lights positioned between 2 and 4 ft off the ground.