I'm afraid I can't reliably see small bits of brown glass even in the daytime, at any significant speed Other than that, in full darkness on dry pavement with no competing lights, and all my lights turned on including the DBS V2... probably 40mph or thereabouts. Let's call it 35mph to be safe I have over 2000 lumens available when I don't have lights out on loan, but routinely use only about 1200.