So Are Bike Lights definitely Necessary?
After dark, yes. A thousand times yes.
In the UK, bike lights after dark are not only extremely sensible, they’re a legal requirement according to the Road Vehicles Lighting Regulations.
Meanwhile, Rule 60 of the Highway Code states:
“At night your cycle MUST have white front and red rear lights lit. […]Flashing lights are permitted but it is recommended that cyclists who are riding in areas without street lighting use a steady front lamp."
The lights also need to be fixed to the bike. That means that lights that fit onto your helmet on the back of a rucksack, while helping you be more visible, do not meet the legal requirements for bike lights. You can of course use these lights as additional lights for added visibility.
Another thing to note is that you also need rear and pedal reflectors if cycling at between sunset and sunrise. Bikes will come with reflectors fitted but it's definitely something to bear in mind if you've upgraded our pedals.
ARE BIKE LIGHTS NECESSARY DURING THE DAY?
Legally speaking, no. Light manufacturers increasingly have ‘day time modes’ involving a bright strobe effect, but whether or not a cyclist uses them is a matter of personal preference. Some people feel safer, and others feel it is unnecessary.
STREET LAMPS ARE NOT ENOUGH
Some people (we’ll call them “night ninjas”) assume that if they’re cycling without lights but under street lamps, drivers will be able to see them anyway. That just isn’t the case. In fact it can be extremely difficult to spot a slow moving dark shape on the road, and cycling without lights is dangerous.
BRIGHT FRONT LIGHTS ALSO HELP YOU SEE
It’s great to be able to see exactly where you’re going. It may seem obvious, but a bright front light – say, of 200 lumens in the city or 600 off road – will allow you to spot pot holes, broken glass, and maybe even an abandoned £20 note.
WHAT’S THE MINIMUM LIGHT OUTPUT I NEED ON MY BIKE?
Front Light: A flashing light needs to be at least ‘4 candelas’, which equals roughly 50 lumens, which is fairly modest. A bike light that can put out a steady light should be marked as conforming to BS6102/3 or an equivalent EC standard (read more about this on Cycling UK). Lights from reputable brands such as Cateye, Lezyne, Exposure, and Moon meet this standard.
Rear Light: Rear lights in general emit fewer lumens than front lights, but if they are flashing then they must also emit at least 4 candelas. Again, lights from reputable brands such as Cateye, Lezyne, Exposure, and Moon meet this standard.
For more guidance on how bright your cycle lights should be, take a look at our blog: What Bicycle Lights Do I Need?
CAN A BIKE LIGHT BE TOO BRIGHT?
Legally speaking, it’s somewhat open to interpretation. The Road Vehicles Lighting Regulations say it is an offence for vehicles (any vehicles) to cause “undue dazzle or discomfort to other persons using the road”.
Morally speaking, it’s nice to be nice, and it’s also nice to not cause other people to have accidents. Nobody likes to be blinded by someone else’s lights. When riding on shared paths in particular, dip your lights down instead of pointing 1,000 lumens straight at people’s faces (including other cyclists.)
If you want to geek out on the brightness of bicycle lights, here’s a good article by Chris Juden called ‘Dazzling Bike Lights’.
WHAT ABOUT DYNAMO LIGHTS?
Dynamo powered lights are lights powered by a dynamo hub built int o the front wheel of your bike. If you buy a bike by a brand like Kalkhoff, it will come fitted with a Dynamo light. These are legal – even if they don’t have the ‘standlight’ technology which means the light doesn’t immediately go off when you stop riding e.g. at traffic lights. The benefit of a dynamo light is that you never need to replace the batteries or recharge it.