Since flashing was legalised, you are now allowed to use almost any kind of light on a bike, provided you don’t put a red one on the front or any other colour on the back, and provided it doesn’t dazzle other road users. If it flashes, it must flash between 1-4 times per second.
Fitting what you’re allowed to fit won’t necessarily make your bike legal to ride in the dark. For that you need at least one front and one rear lamp that is approved. (You’ll also need a red rear reflector and yellow pedal reflectors.)
A lamp is approved if it has a mark to say it conforms with BS6102 part 3, or the marking of another EC country, provided their approval system ensures a corresponding level of safety. There is only one other country of which that can confidently be said and it’s Germany, where each approved design gets an individual approval number prefixed by ‘K~’. The good news is that lots of lights have German approval. The bad news for battery-loving Brits is most of them are dynamo lamps.
It may surprise you to hear that it’s also possible for a flashing lamp to be approved. And since BS6102 doesn’t cater for flashing, these lamps get approval simply by claiming to emit at least 4 candela. They don’t even need any official markings! Unfortunately, most flashers also have a steady mode and since the authorities like to apply a proper standard whenever they can, in that case they need to conform to BS. As far as I know, the only purely flashing light that can claim approval simply on the basis of being bright enough is the Reelight SL120.
Once upon a time, Britain and British Standards ruled the cycling world. Nowadays even the few, new British manufacturers of cycle lamps don’t bother with BS approval for their products. Why should they? The lamps are perfectly legal to sell and to use; and so long as they shine okay, which mostly they do, the police will be happy. The only time anyone looks for approval marks is after an accident. What happens then, we don’t know. You’ll be riding illegally of course, but I would argue that such strict adherence to the law is no longer reasonable, now that approved battery lamps are like needles in haystacks!
The last time I checked, one large online retailer was selling 148 different bike lamps, only three of which were approved. But Cat-Eye no longer make those models so it’ll probably be zero now. Note that the CE mark has nothing to do with a lamp’s performance as a lamp and merely implies that it shouldn’t poison, stab or electrocute you!
The good news is that the Dept for Transport is at last beginning to talk to us about the deregulation of cycle lighting. Until then, the easiest way to be legal is to fix a set of Reelight SL120 around your hubs, then fit whichever really useful (but unapproved) lights you like on the rest of your bike. Or fit a dynamo, where most of the lamps on the market are German-approved and excellent. However there are a few battery lamps, adapted from dynamo lamp designs for use on racing bikes in Germany, that also have a K~number – such as the Busch & Müller Ixon-IQ front and D-Toplight Permanent rear.
This was first published in the December 2012 / January 2013 edition of CTC's Cycle magazine.