OK.
This is the reply I got from Cateye when I asked if their lights and specifically the one I have, the VIZ450 was for road use and legal :
"
CatEye lights (including the VIZ range) are intended for both daytime visibility and night-time road use. The VIZ 450 is a
rear red light, rated at 450 lumens peak output, with multiple modes (steady, flashing, group ride etc.).
It complies with general UK cycle-lighting standards provided it is:
- Mounted facing rearwards.
- Emits red light only.
- Visible from a reasonable distance (up to 50 m + easily met).
- Used with an approved steady mode when riding at night on the public highway.
The relevant law is
The Road Vehicles Lighting Regulations 1989 (RVLR).
Key points:
Night riding (between sunset and sunrise)
You must have:
- White front light
- Red rear light
- Red rear reflector
- Amber pedal reflectors (front and rear of each pedal, unless bike type makes this impractical such as clipless MTB pedals)
Your rear light must:
- Emit a steady red light or a flashing red light (flashing allowed if it flashes at least once per second and has a luminous intensity ≥ 4 candela — which most CatEye models exceed easily).
- Be mounted centrally or offside (right-hand side), and clearly visible from the rear.
There are no specific lumen limit in UK law — the RVLR only specifies
minimum visibility, not maximum brightness.
However, you
can technically commit an offence under
Regulation 100 of the Road Vehicles (Construction & Use) Regulations 1986 (or the more general offence of “not using lights so as to cause danger or undue dazzle”) if a light is
likely to cause undue dazzle or discomfort to other road users.
For context:
- A 450-lumen rear light is very bright — excellent for daytime visibility but can be too intense at night if angled directly at following drivers.
- This is why CatEye include “Group Ride” or “Low” modes, usually around 20–50 lumens, specifically intended for night-time riding to avoid glare.
Practical advice:
- Use the lower-intensity steady or flashing mode at night.
- Angle the light slightly downward so the beam is aimed at bumper height rather than straight into drivers’ eyes.
- Use the brightest mode only for daytime running or foggy conditions.
That will ensure your light is both
legal and
considerate.
So long as it’s mounted properly and used in a non-dazzling mode at night, it meets all legal UK requirements."
So there you go. The Cateye lights are intended for road use and they are legal.
Who'd have thought eh.