Trek has researched extensively the best ways for riders to be noticed. Their conclusion - If you do nothing else, at least use daytime running lights. Daytime running lights make riders 2.4 times more noticeable than no lights at all.
What makes a good daytime running light?
Focus: Lumens aren’t necessarily the most important indicator of a great light. Take a laser beam for instance. A small pen light with a focused laser beam can be seen in daylight better than a much brighter flood flashlight. Bontrager focuses their beams to take advantage of this technology to make us more visible during daylight hours.
Flash: Flashing lights are definitely more noticeable than a constant beam. And an interruptive flash pattern with varying beam intensities is more noticeable than a steady flash. Bontrager has taken these findings and built a unique flash pattern into all of their daytime running lights.
Range: The sooner a driver notices you, the more time they have to react to you. Bontrager daytime running lights, with their focused beam and unique flash patterns, give cyclists the ability to be seen from as far as two kilometers away.