British summer time brings with it long, balmy evenings, extended commutes home anda reduced need for bike lights. Except maybe not that last one - thanks to the growing popularity of daytime running lights (DRLs).
Unlike the daytime running beams that have been compulsory on cars and vans in Europe since 2011, they're not a legal requirement for cyclists - but many brands argue that they're a very good idea - especially when considered alongside the fact that 80 per cent of accidents involving a cyclist happen in daylight.
What's the evidence that daytime running lights work?
It's hard to determine the true percentage drop - with vast differences between stats given - but most available studies seem to suggest running lights in the day can reduce collisions.
A 2012 study carried out in Denmark discovered a 19 per cent drop in accidents when cyclists used permanent running lights.
When it comes to use in vehicles, results vary - some studies showa five to 10 per cent reductionwhilst others demonstrate an accident rate drop of 28 per cent. One study carried out by the USNational Highway Traffic Safety Administration found at 23 per cent drop in accidents involving motorcycles and cars when day time lights were used.
Philip McAleese, CEO of See.Sense, a brand that makes smart lights with a clever day time mode, is of course an advocate of cyclists using lights at all times.
He told us: "We [at See.Sense] find the evidence quite compelling. Our customers also tell us that they experience fewer close passes when using our products. The challenging part is getting over our own subconscious bias. If you said, 'cars should be visible in the daytime' no one would bat an eyelid. And yet, cars do benefit from daylight running lights to make them move visible. If something as large as a car needs it, then perhaps it's not such a stretch to believe that cyclists can benefit from them too."
Rory Hitchens, of Upgrade Bike - UK distributor for Lezyne lights, said: "in the UK we have a particular need for daytime lights because we have a real mix of weather and a lot of “flat” grey dark days. Also we have a lot of traffic on our roads and a lot of cyclists.
"I would recommend using them on every ride. With better burn times, outputs and battery technology, there really is no excuse not to."
It's important to be clear, however, that not everyone is in favour of DRLs.
Sam Jones, at Cycling UK - the National charity for cyclists - told us: "If people find they make them feel more comfortable on the road, they should do what makes them feel safer – but our stance is that if you’re cycling where you should be – further out into the road and not hugging the pavement – your positioning should make you visible enough.
"Around ten or eleven years ago we ran a campaign opposing daytime running lights for cars – we’re not convinced there’s evidence to suggest they reduce collisions, and we think they could have a detrimental effect for cyclists and pedestrians – if people become accustomed to looking out for lights, they might not see the wood for the trees. In terms of cyclists, they could be a deterrent as there's an added cost involved."
He added: "You must of course use lights once the sun dips below the horizon, so we’d always suggest packing a set if you're heading out for a long ride – as you never know what might happen."
What's different about 'day time running' lights?
If you do decide you want to run a DRL, then there's good news: the majority of bike light brands now offer lights with a daytime running mode as standard.
This is not as simple as using your normal light, during the day. However, there are different schools of thought on how the light pattern should be different.
"We've been creating daylight visible lights since 2013. In the last 12 months we've seen the marketing machines of the big companies jump on the bandwagon with various 'special' flash modes. What lights really need, is to be bright. This in turn needs a lot of energy, so you end up with a large heavy battery or a short runtime," said See.Sense'sMcAleese.
"We developed a different approach - we know that most cycling collisions occur during daylight hours, at or near road junctions and in urban areas. So we used sensors and artificial intelligence to give our lights awareness of their situation so they can flash brighter and faster in response to their environment, flashing brightest when you most need to be seen. Our approach is not marketing, it's so novel that it's patented," he added.
Other brands opt to vary the flash pattern in an attempt to draw more attention in daylight hours.
Bontrager - the accessory arm to Trek - claims that a flashing light is 1.4 times more effective than a steady beam.Whilst most lights use a flashing pattern, its day flash mode has been created specifically to make the beam more noticeable byvarying outputs on an interruptive flash pattern.
Similarly, Lezyne uses what it calls "Engineered Visibility" - in which the flash sequence gives two bright, then one super bright flash - in the same vein to offer an interrupted pattern that increase visibility - and increases burn time (battery life) too.
Lights intended for use in the daytime need to have a greater output than those used in the dark, in order to stand out. Therefore most daytime modes boast a higher lumen output.
Side visibility is also something worth looking out for, as this provides greater visibility at junctions - where a whopping 75 per cent of accidents occur.
Hitchens advocates using a light on both the front and rear of the bike, saying: "if you only had one light then the rear is more useful because traffic is on your side of the road from behind [but] cars pulling out of a junction need to see you coming, just as much as cars from behind."
McAleese agrees, saying: "personally, I always run a front and rear set as it's better to be seen than to be missed."
Just daytime running lights?
If you're convinced on DRLs, you might be wondering if they negate the need for other visibility aids during the daytime - such as visible clothing.
When Trek launched its Bontrager DRL it commissioned Clemson University to carry out research into elements that could help cyclists be seen and thus reduce accident rates - though it did open the discussion with the statement that "per mile ridden, cycling is getting safer. But until there are zero fatalities, there is still work to be done."
Clemson University came back with three clear recommendations - firstly, for DRLs, secondly, clothing that highlighted moving parts (shoes, overhshoes, gloves, arm warmers), and thirdly choosing gear that contrasts with the environment.
Hitchens comments: "Personally I am a fan of both [lights and high viz clothing]. This is my personal opinion… I think that lights have the chance to stand out more in a way because when high vis is spotted, specially neon yellow which is common, the driver has a tendency to think 'oh it’s (only) a cyclist'. Whereas when a daytime flash is seen there is the question mark about what it is, then paying it attention more. Our roads are so full of visual pollution with bill boards, road signs, shop signs etc that getting noticed is like visually warfare. Lights stand a better chance."
Best daytime running bike lights
See.Sense Icon+ front and rear set - RRP £149.99
See.Sense bike lights are 'be seen' beams that use an accelerometer to react to situations on the road - they flash brighter and faster at roundabouts, road junctions and in response to approaching car headlights at night. The front provides 420 lumens and the rear a staggering 250.
Lezyne Strip Drive Pro 300 - RRP £49.99
Compatible with both round and aero seat posts, the Strip Drive can deliver up to a whopping (that's one step up from staggering) 300 lumens. There nine different modes, including a daytime flash and the light's memory means it'll always return to the last mode you used.
Bontrager Flare R USB rear light - RRP £45
Bontrager championed the daylight running lights conversations early on. Its Flare R rear light outs out 65 lumens, and offers 270 degrees of visibility, with a claimed range of 2km in day time and 5km at night. There are a range of day modes, designed to use disruptive light patterns, as well as several night modes. Max battery life is 21 hours on a low steady beam, whilst the lowest day time mode lasts ten hours.
Four4th Scorpion rear light - RRP £95
The Four4th Scorpion rear light came to our attention when marshalling time trials. It's mega bright - there's three modes, TT, lone riding, and group riding. TT is the brightest, and alternates between red and green flashes at 122 to 491 lumens. It's incredibly bright, but does come with a disclaimer: the law requires red lights only so technically it's outside of that. Group and lone modes use red lights only. The light fixes to the saddle rails so fits with any seat post.
Exposure Trace and TracR set - RRP £74.95
Putting out 100 lumens at the front and 75 at the rear, Exposure's Trace and TracR set comes with three brightness modes, solid or pulsing lights and a special daylight setting.
They're charged via a micro usb and fitted with a quick to remove elastic band.
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Cycling Weekly's Digital Editor Michelle Arthurs-Brennan is a traditional journalist by trade, having begun her career working for a local newspaper before spending a few years at Evans Cycles, then combining the two with a career in cycling journalism.
When not typing or testing, Michelle is a road racer who also enjoys track riding and the occasional time trial, though dabbles in off-road riding too (either on a mountain bike, or a 'gravel bike'). She is passionate about supporting grassroots women's racing and founded the women's road race team 1904rt.
Favourite bikes include a custom carbon Werking road bike as well as the Specialized Tarmac SL6.
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