Yes, absolutely! Again, as a truck driver, I recommend that every cyclist use lights in the daytime. Batteries are cheap. Like you say, Stapfam, you can be seen for great distances with the use of either the red rear lights or the headlights. Just yesterday, four of us went out to the country for a 50 miler. Lots of dark shady areas that would burst into the sunlight. A driver with a moderately dirty windshield can easily be blinded by the afternoon sunlight in such cases. Those red blinkies are amazingly visable at over a 1/4 mile at least.