A headlamp duct 28 is connected with engine ducting 2 between air inlet 40 and ducting outlet 42 which is coupled to the engine. Headlamp duct 28 receives airflow 13 from engine ducting 2 and directs airflow to vehicle headlamp 30. A valve 6 disposed between headlamp duct 28 and engine ducting 2 is displaceable between a first position and a second position, whereby in the first position valve 6 permits airflow to headlamp duct 28 to be discharged toward vehicle headlamp 30, and in the second position valve 6 occludes airflow more to headlamp duct 28. Valve 6 is preferably responsive to air pressure in engine ducting 2. At low engine throttle, valve 6 permits airflow to headlamp duct 28 and at high engine throttle valve 6 is displaced to the second position, increasing air flow to the engine.