The invention provides a headlight device capable of generating two distinct, though possibly overlapping, beam portions, by means of a single integrated unit. The unit comprises two primary optical components for generating the two respective beam portions, and a single exit lens through which the combined beam is transmitted. A low beam having a stepped cut-off—to avoid glare to oncoming road users—may be generated by means of the provided device, with the cut off generated by means of a specially shaped collimating element, and the remaining spread of the beam generated by means of a downwardly reflecting reflector. Dual high and low beam functionality can alternatively be achieved, wherein the collimating element generates a high beam, and the reflector structure generates a low beam. By shaping and positioning the collimating element appropriately, a stepped cut off in the low beam may be still be provided in these embodiments.