JRA with the Angry Asian: All daytime lights are not created equal

by James Huang


I’ve made it plainly clear over the last few years that I’m a big fan of daytime running lights (DRL) when it comes to riding on the road. While they obviously can’t physically prevent a driver from hitting you, they at least make you more conspicuous so that you hopefully stand a chance in the fight for attention between what’s on the road, and what’s on the driver’s phone. That said, it’s also impossible not to notice that there’s a huge amount of variability in terms of real-world visibility. Shouldn’t there be some sort of industry-wide requirement in terms of what can — and can not — be described as a true DRL?


US-36 is the main paved route out of town here in Boulder, Colorado, and on any given weekend day during prime riding season, there are hundreds — maybe thousands — of riders rolling along the shoulder of the road, heading off to parts unknown. Safety is clearly on a lot of their minds, as I’ve noticed that a lot more of them these days are donning some combination of high-visibility clothing and/or daytime running lights.

Or rather, what many of them think are daytime running lights.

This image was taken from a distance of about six car lengths. Without the DRL, how visible would this rider be to an approaching car, and how much time would a driver have to react?

Unfortunately, many of those lights aren’t nearly bright enough. Granted, the midday sun here in high-altitude Colorado is unusually intense, but I’m still actively looking for those things, and yet with disturbing frequency, I often don’t notice them until I’m within a handful of car lengths. Those riders clearly think they’re making themselves more visible by fitting a light to their bike, but it’s very much a false sense of security.

And sadly, it’s probably not the riders’ fault.

Rider safety is an awfully hot topic at the moment, and more than a few companies seem keen to cash in on the newly widespread consumer interest in DRLs. The idea of a DRL makes a lot of sense. But what exactly constitutes a DRL?

Knog was an early pioneer of LED “be seen” lights, with its original silicone-wrapped Frog light arguably putting that company on the map. When you look at the company’s product page for rear lights today, you’re greeted with the following description (emphasis mine):

A range of bright rear bike lights. Compact, USB rechargeable and waterproof lights with side illumination for added visibility. Suitable for night and daytime riding.

The highest-powered light on Knog’s list is the Blinder Road R70, rated at 70 lumens. From firsthand experience, it’s a seriously bright unit and easily visible from a generous distance in bright sunlight. However, also included in the list is the Blinder MOB StVZO, which puts out barely a tenth of that. That little Frog was cute and all, and certainly better than nothing if you were caught unexpectedly riding after dark, but it otherwise was little more than a toy in terms of its daytime effectiveness. Nevertheless, its 8.5-lumen claimed output is actually greater than the MOB StVZO.

Similarly, Blackburn’s collection of rear lights is headlined by the Dayblazer 125, which, as the name suggests, pumps out a whopping 125 claimed lumens, and is the brightest rear light the company has ever offered. I can say from firsthand experience that you don’t want to look directly into it. But at the same time, the Click rear light — with a claimed output of just four lumens — is supposedly “incredibly visible to drivers.”

Even the marketing collateral from Bontrager — one of the industry’s foremost champions of the DRL concept — is pretty unclear. While the top-end Flare RT is rated at 90 lumens, the entry-level Flare 1 only puts out five lumens, but yet it still lets you “pedal with confidence through the day.”

Lezyne’s rear lights are thankfully described somewhat more realistically. Its 75-lumen KTV Drive Pro is clearly indicated to have a “Daytime Flash” mode, but none of the rear lights with less power are advertised explicitly as being suitable for daytime use.

“When we first introduced a light with Daytime Flash (6 years ago), we had established internally that 70 lumens (for a taillight) was the minimum output to be effective during the day,” said Lezyne worldwide marketing manager Dillon Clapp. “But what really makes DRLs noticeable is their flash patterns. We feel that is just as important as the output. So we continue to make brighter and more disruptive DRLs, but wouldn’t consider anything lower than 70 lumens to be bright enough on a bright day.”

Surely there are some industry guidelines on the subject, no?

The wild west

Some industry standards regarding bicycle lights do exist, such as the German Straßenverkehrs-Zulassungs-Ordnung, or StVZO, and the ANSI FL1. But the FL1 standards only dictate how companies measure the claimed output of their lights, and StVZO is mostly a set of guidelines on front light brightness and beam pattern cutoffs, and restrictions on rear light flashing patterns. An increasing number of companies are voluntarily adhering to FL1 guidelines for stated output, which is great, but StVZO does little to promote cyclist safety as most of the guidelines are in place so as not to blind drivers, not explicitly to make riders more noticeable to vehicular traffic.

Otherwise, it’s basically a free-for-all in terms of what companies can and can not claim in regards to DRLs.

The lowest-power rear light in Bontrager’s family of daytime running lights, the Flare City R, puts out 35 lumens and is supposedly visible at a distance of up to 900m. Even so, Bontrager only recommends this model for city or urban use where automobiles are traveling at slower speeds. On open roads, Bontrager recommends riders use the much brighter Flare RT, which puts out 90 lumens and is supposedly visible during the day up to 2km away.

“Yes, there is a lot of confusion throughout the industry about daytime running lights,” said Bontrager product manager Alex Applegate. “Simply taking a tail light and using it during the day does not make it a daytime running light. To be effective, you have to have intentional design that was made, from the beginning, to be able to be seen and noticed during the day, and from a meaningful distance. We say at least 400m, and all of our daytime running lights are third-party tested to be seen beyond that. We use focused lensing, interruptive flash patterns, meaningful ranges, and whole lot of testing and validation — both through university partners and independent third parties — to ensure our lights effectively perform as we expect them to.”

“You are entirely correct in your assertion that there are currently no official regulations in terms of DRLs,” said Knog’s brand director, Louis Philo. “Being a highly compliant business, Knog would certainly welcome such regulations, which would help clarify the claims made by the myriad of bike light suppliers. Essentially, it is our belief that any light used during the day is better than none, even our lights with the smaller lumens, such as the Blinder Mob with its 11 lumens.”

“It’s not accurate to say X lumens or below is not a DRL, and above X lumens is a DRL,” said Mark Matson of Blackburn. “There are other factors at play. The main construction difference that enhances visibility would be the focused beam using a TIR (total internal reflection) lens on the Dayblazer rear lights, which is not used on other rear Blackburn models. In the same way most front, ‘to see’ white lights work, the Dayblazer’s red light beam is more concentrated, pointing behind the bike towards cars. That focused beam increases visibility in daylight hours.”

Yep, fair enough, there’s much more to daytime visibility than just lumen output when it comes to DRLs (as mentioned above by Lezyne’s Dillon Clapp). Unquestionably, flashing patterns and how the light is focused make a big difference, too. But a weak light is a weak light, full stop, and no amount of focusing or blinking technology can hide that.

A guessing game

Given the lack of any sort of industry standard in terms of DRLs, it should perhaps come as no surprise, then, that riders aren’t always sure what’s effective when shopping for one.

“I have small Knog blinders front and back,” said CyclingTips VeloClub member Ben Jensen. “I took the LBS guy’s word for it they’d be bright enough to be seen.”

Another VeloClub member, Dan Tan, takes a decidedly conservative approach, using some combination of Exposure TraceR, See Sense Ace, and the latest-generation Cycliq Fly6 on his bike, plus a Knog Blinder attached to his backpack. But even so, there’s a troubling lack of confidence in the lights’ effectiveness.

“I’m not sure how visible these are,” he said. “You need a pretty high brightness for daytime run lights, especially here in Australia during summer.”

Just because a company’s marketing materials claim that a light will help make you more visible during the day doesn’t make it so. This Blackburn Click model puts out a meager four lumens, and I refuse to believe that it’ll provide anything during daylight hours other than a false sense of security. Photo: Blackburn.

Several VeloClub members just based their decisions on firsthand observation — which, in the absence of any sort of industry-standard rating system, is actually a really good idea.

“I use a Bontrager Flare RT rear light all the time,” said Dhruv Chanchani. “I saw some others use it on a group ride, and up in the mountains, it was amazing to spot it up ahead from a distance. It was way more obvious than the hi-viz clothing even. Seeing that light so clearly between bends and switchbacks as the other guy pulled way ahead of me really sold me on it.”

Chanchani’s suggestion is undoubtedly a good one: if a light is visible to you from a distance, it’ll likely be visible to someone else at a similar distance. But that said, none of us should have to resort to that sort of research, and even if you spot a super visible light off in the distance, it’s not always possible to catch up to that rider and find out what they’re using.

DRLs need an industry standard

The bike industry is littered with impressive-sounding marketing claims, and as much as many of them make me roll my eyes, I’m not always offended by them because the claims are usually performance-based. But what I’m not ok with is companies willfully encouraging a false sense of security — rider safety is not to be toyed with.

So what’s the takeaway here? Daytime running lights can potentially help riders stay more visible to vehicular traffic on the road, but only if they’re sufficiently effective in terms of brightness and/or flashing patterns. Either way, riders shouldn’t be forced to guess if a DRL is doing its job, and they certainly shouldn’t be sold any light believing it works when it doesn’t.

See Sense, out of Northern Ireland, produces nothing but daytime running lights. Its lowest-power rear option puts out 125 lumens, and its brightest model puts out an impossible-to-ignore 300 lumens. This first-generation Icon model was recently discontinued, but still churns out 190 lumens.

For sure, no DRL can actually keep an inattentive, incapacitated, or malicious driver from plowing into you. But when the point is visibility, I sure as hell want to know that what I have on my bike actually does what it says — and right now, we all unfortunately have little more to rely on than faith and marketing claims, neither of which should make any of us feel any better.

“Just slapping a badge on or reshaping the marketing message of an existing light does a consumer an injustice,” said Applegate. “An industry standard would help ensure that consumers get what they are expecting, and likely bring up overall performance across the industry. Studies show that cyclists are prone to overestimate their visibility, often overconfident that they can be seen. Knowing this makes it all the more important for products that are designed and marketed to help with rider visibility live up to their expectations in meaningful ways.”

I love a lot of what you do, Knog, but I’m sorry, your, “any light used during the day is better than none” argument — and any other company that adheres to a similarly poor argument — just doesn’t cut it.

Ball’s in your court now, bike industry.

Footnote: Bontrager agreed to clarify the wording on the product pages of their lower-powered rear lights after our discussion.

JRA is an acronym well known to bike shop employees, usually applied to customers submitting warranty claims that are clearly invalid (“I was just riding along when my top tube dented!“). It’s in part an homage to James Huang’s long tenure as a shop mechanic, but also the title we’ve given to the collection of random musings that will regularly be published here on CyclingTips. Most — but not all — of them will tech-related, but either way, they’ll reflect what’s been on his mind and what he’s been thinking about when he’s just riding along.

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