Front and Back Flashing if on the road. Both solid if on the bike trail. Especially in the winter (to see road, ice, etc. better...and be more noticeable) I'll also usually supplement with a dedicated headlight that is bright enough to see the road. I currently use a cygolite. I direct the cygolite towards to road (to see) and don't flash it (despite the setting)...it is painful in flash mode.