I don't know any cyclist who would be on their bike at night without powerful lights, often several of them. Riding with daytime running lights is an entirely different subject. Bicycling Magazine, May 2017, cites a stat asserting 80% of cycling crashes occur during the day. What are we doing to make ourselves more visible. It seems most people use some form of rear light during the day. How visible the light might be is another subject entirely. Most of the lights I see appear to have been purchased with price being the prime consideration. They're just wimpy and, frankly useless. A growing body of research is indicating highly visible front and rear lights for daytime use will make you much more visible and less likely to be hit.
My reading indicates it is not just lumens we need to measure. The effectiveness of any light is a combination of "focus, flash and range."
Focus is a measure of the concentration of the beam. Generally the more focus the more forward visibility, like a flashlight. But there are also concerns about being visible by vehicles approaching from the side, not just from the front. Too much focus will minimize the light's side visibility. As in all things, the amount of compromise here is personal.
Flash is the quickness and frequency of the pattern created. There is clear evidence a flashing pattern during the day will increase the chance of being seen. Remember the goal is for an inattentive driver to recognize us as a human in motion. We do that by making our self stand out against the background clutter entering the driver's visual field. They are not looking for us and we must attract their attention. It is clear a flashing pattern works best.
Range is the distance the light will be seen. Many consider the minimum distance a light should be visible during the day is 1/4 of a mile. I would argue for much more.
Remember there are no accepted industry standards here. Personal preference and cost will determine.
Here are Some Bicycle Lights to Start Your Search:
- Bontrager's Flare R Tail light and ION 800 headlight (designed for daytime use)
- Zecto's Drive rem LED (on the low end at 20 lumens)
- Cateye's Rapid X2 Kinetic LED rear light (50 lumens)
- Blinder Mob V Mr. Chips (44 lumens) which they claim can be seen 1.2 km away in daylight
- Lezyne's Strip Drive Pro (150 lumens)
- Lupine's Rotlicht (160 lumens)
- See. Sense's Icon and Garmin's Varia (both sense traffic and adjust brightness and flash)
For more details check out Cyclingtips.com/See and be seen: what every cyclist needs to know about daytime running lights (Feb 17, 2017)