If you're after a front light, we've got you nicely covered. But what about a red one for the rear of your bike? Don't worry, we're all over that too!
Get yourself seen
A rear light has the proverbial one job: to get you seen, unlike a front light that has to be visible enough to stop inattentive drivers mowing you down while allowing you to see where you're going. Depending on where and how you ride, your priorities regarding brightness, flashing modes and battery life will be different.
The Road Vehicle Lighting Regulations say:
One is required, to show a red light, positioned centrally or offside, between 350mm and 1500mm from the ground, at or near the rear, aligned towards, and visible from, behind. If capable of emitting a steady light, it must be marked as conforming to BS3648, or BS6102/3, or an equivalent EC standard. If capable of emitting only a flashing light, it must emit at least 4 candela... the light shown by the lamp when flashing shall be displayed not less than 60 nor more than 240 equal times per minute and the intervals between each display of light shall be constant.
Given that every light we know of has a steady mode, that means you need an British Standard-approved light to comply with the law. To be fully compliant with the law your bike also needs a front light, front and rear reflectors, and amber pedal reflectors.
In practice, not many bike lights are Kitemarked. The specification for cycle lights dates back to 1986 and is written mostly with filament bulbs in mind; every single light we've been sent for the last few years is an LED. LED lights can meet the requirements but lots of them aren't specifically tested for the ageing British Standard, especially those that are sold worldwide.
Since the Road Vehicles Lighting Regulations (RVLR) was amended to allow cyclists to fit flashing LEDs, we've heard very little about cyclists being stopped for having non-compliant lights. In theory running a non-approved light could be used as an argument for contributory negligence in the case of an accident, though we've not heard of such a case being brought as yet.
Things to consider
What kind of riding will I be doing?
If you're mostly just pootling to the shops and back then something basic will probably do the job. Simple flashers that use button cells or AAA batteries are cheap and effective these days, and they last ages before the battery needs replacing.
If your commute is on busier roads, or you plan to do longer rides at night, you'll probably want something brighter. There's a wealth of USB-rechargeable and brighter AAA-powered rear lights about that will catch a driver's attention from further afield. Many riders who spend a lot of time on the road after dark fit more than one rear light to increase their chances of being seen.
Some rear lights are bright enough to be used in daylight too. There's certain types of riding – racing a time trial on a fast A-road, for example – where you'd want to be running the brightest rear light you can buy. Plenty of city riders run their rear lights in daytime hours too.
Flashing or not?
In terms of the law, it's up to you. The law requires flashing modes to be between 1Hz and 4Hz (one to four flashes per second); as you'll see from the beam comparison engine below, actual modes vary considerably and some fall well outside that. Pulsing constant modes are a grey area.
Ask a rider why they have their light flashing and they'll often argue that it makes them visible from further away. Ask another rider why they have a constant light and you'll often hear that it makes distance easier to judge for following vehicles.
There's not a lot of scientific research to hang your choice on. Most people who run two lights will have one of them flashing. One thing to bear in mind is that if you're riding in a close group – be that a club run, sportive, Audax or anything else – having a bright light flashing in your eyes at close range is pretty annoying. Many lights have low-power steady modes for group riding.
Most rear lights are nice and bright if you're standing directly behind them. But in many situations – and especially for urban riding – traffic may be approaching you from other directions, so it's good for a light to have a wide angle of visibility. Again, the type of riding you do will dictate how important side visibility is to you.
Most rear lights will cope easily with the longest ride you're likely to throw at them, though not all USB-rechargeable ones can be fully trusted to last a whole night, especially on steady beam. If you're planning some big forays into the dark unknown – or if you're just a bit crap at remembering to charge your lights – pick something that has a long run time. AAA-powered lights tend to be the pick for that.
The Moon Alcor is simple, bright and has a nifty magnetic mount. I use a back light almost all the time, perhaps excepting on the finest of high summer days. Bright sunlight, especially when the sun is low and the roads are wet, is not the friend of the cyclist and an attention-grabbing strobe like that provided by the Moon Alcor is a valuable aid to daytime visibility.
That's how I've used this most of the time during the test period, and it was a bonus that the day-flash mode gives over 34 hours of battery life (I never did find out exactly how many hours because I had to go to bed). Moon reckons that on the low-power single-flash setting you should get 70 hours. That's still plenty bright enough for night riding on dark roads, by the way.
The Oxford Ultratorch Pro R25 LED Tail Light is a strip rear light that performs the basics very well at a competitive price.
What do we want from a rear light? For me, there are only a few central criteria that it needs to fulfil to hit the spot: it needs to be bright, make you clearly visible, and fit securely to the rear of the bike. Next comes battery life – something easily taken care of usually, thanks to the lower power requirement of a tail light compared to a front beam – profile on the bike, and waterproofness.
The Ultratorch meets pretty much all these criteria. A single button atop the unit operates the light, in which you can cycle through four different settings with a single click – three static brightness settings of 25, 50 and 100 per cent of the 25-lumen maximum output, and a 12-lumen flash setting from the Cree LEDs.
The Bontrager Flare R City rear light is a small yet mighty cube-shaped model bristling with sensors and similar tech to deliver optimum light intelligently, whatever the conditions, day, or night.
The tail light has a 100-lumen front sibling, and together they could be all some urban commuters will need. At 26g apiece, they're arguably ideal clutter-free options for summer/time trial builds, or companions for a trainer/audax bike's main lighting.
Brightside's Bright, Amber and Sideways is a well-built double-ended side light at a good price that attaches easily to your frame, and gives you an extra dimension of visibility to other road users approaching you from the side. Bright 15-lumen Cree LEDs at each end attract attention.
The Brightside has filled a gap in the market (a quick internet search only unearthed the Brightside and the Cateye Orbit Spoke lightset) in a bid to reduce the instances of SMIDSY (sorry mate I didn't see you) incidents. With too many accidents happening at junctions and roundabouts, the light is designed to give you all-round visibility to motorists approaching from your side – Brightside, not broadside.
A classic that's still going strong, the TL-LD600 has five decently bright LEDs and runs off a pair of AAA batteries. It excels as a round-town attention-grabber because of the mode in which the lit LED scans across the panel: think Knight Rider or Cylon Centurion.
Moon's Gemini is a featherweight USB rechargeable rear light that clips on easily and is bright enough for urban commuting. The small single button is surprisingly easy to find in big gloves.
The Gemini benefits from many of the features of its more expensive big brothers. It has a spot angle of 95 degrees at 10 metres, giving an effective span of 22m. The total angle is helped by the two single LEDs, resulting in a full 360 degrees, very useful for urban riding. The brightest 20-lumen constant is also perfect for partially lit commutes; I prefer a slightly brighter rear for my unlit rides, but this also works well here as a backup or secondary light.
Literally a great all-rounder, the KOTR 25 is visible from a full 180° and makes superb use of its 25-Lumen output.
Dr Evil would love it. As well as powerful two-watt LED, the Sentinel shows riders how much space you'd like them to leave when they pass by drawing a virtual bike lane on the road with frickin' laser beams. Shark not included.
The Knog Blinder Mob Kid Grid Rear Light is a well designed and strong performing rear light. It pumps out enough light to keep you visible and has a really good variety of placement options while also having a good battery life, so it can just be left for weeks until it needs charging.
The light pumps out 44 lumens to keep you well lit without blinding the person riding/driving behind you. In recent years I have come to realise that being stuck behind somebody pumping out 100 lumens from their seatpost is one of my real pet peeves. Sure you can be seen mate, but the only other things I can see are blue dots. I'd say 44 lumens is about the right balance between good visibility and annoying the person behind you.
This super-bright and tough little USB rear light from UK illuminati Exposure pumps out plenty of light and will last for a week's medium-distance commuting (4-5 miles) between charges. It's not cheap, but it is excellent.
Read our review of the Exposure Lights TraceR & matching front Trace set
Find an Exposure lights dealer
Gemini's Iris rear light claims to pump out a retina-melting 180 lumens of red. That's enough to get you seen in any conditions, and there are plenty of lower-power modes for general riding too. And it's well made.
First things first: ye gods, this thing is bright. You know when you turn a light on, and you think, "MY EYES!"? Well I did that with the Iris, only to find out it wasn't even on the brightest setting.
This is the standalone version of the MJ-818 which uses a 3-watt LED for maximum visibility with nine smaller emitters to cover a wide range of angles. In this package it's paired with a 8.4V 4.4Ah battery. If you already have a Magicshine light, then you can get the light and a cable splitter for £31.94
We loved the clever speed-sensing function and incredible brightness of the original See.Sense 2.0. The Icon includes a plethora of extra features linked to a free app so you can control the light on your smartphone. This nifty little blazer will also tell your loved ones if you have a crash, and alert you if someone tries to make off with your bike when it's parked up.
The Icon uses super-bright twin Cree LEDs running at 95 lumens each, which certainly count as bright enough for the old joke 'do not look at laser with remaining eye'. This is not a light to turn on while looking at it – it is ferociously bright. Amazingly there's also an Icon+ with 2 x 125 lumens to keep you safe, even during daylight hours.
Lupine Rotlicht — £78.18 (€89.00)
Another light with value-added smart functions, the Rotlicht acts as a brake light, brightening when you decelerate, and has a light sensor so it can adjust its output to the conditions. Clever stuff.
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Dave is a founding father of road.cc and responsible for kicking the server when it breaks. In a previous life he was a graphic designer but he's also a three-time Mountain Bike Bog Snorkelling world champion, and remains unbeaten through the bog. Dave rides all sorts of bikes but tends to prefer metal ones. He's getting old is why.