Along the west coast USA during the months following the attack on Pearl Harbor, the fear of a Japanese air attack on coastal cities was palpable. Civil defense efforts mandated completely extinguishing lights with blackouts or minimizing outdoor lighting (including upwardly directed/reflected light) with dimouts. Dark curtains were drawn across windows and the upper half of automobile headlights were painted black to prevent upwardly-directed light.
Civilian adherence to blackout orders on both coasts was mixed, with frequent complaints that blackouts effected businesses and tourism. This was particularly problematic along the east coast in the first half of 1942 where coastal lights actually enabled U-boats to readily identify silhouetted targets. Following disastrous shipping losses, government regulation of night time lighting along the Atlantic Ocean was finally tightened.