A light safe at 40 mph with no other source of light? Are you dreaming? Convert 40 mph to feet per second and you get 58 + 1/3 feet each second (1mph = 1.467 fps). I don't believe there is a bike light in existence that will cover both near and far with enough coverage to be considered "safe". I ride with a focusable XML-T6 flashlight that gives plenty of light even in the few areas I ride that don't have streetlights but certainly wouldn't go really fast even then.