Britain was blacked out on 1st September 1939, two days before the outbreak of war.
During the war, everyone had to cover their windows and doors at night (before sunset) with heavy blackout curtains, cardboard or paint.
They needed to prevent any glimmer of light from escaping and aiding enemy aircraft during the bombing raids.
Street lights were switched off or dimmed and shielded to deflect the light downward. Traffic lights and vehicle headlights were fitted with slotted covers to deflect the beam down to the floor.
Thousands of people died in road accidents. The number of road accidents increased because of the lack of street lighting and the dimmed traffic lights. To help prevent accidents white stripes were painted on the roads and on lamp-posts. People were encouraged to walk facing the traffic and men were advised to leave their shirt-tails hanging out so that they could be seen by cars with dimmed headlights.
Other people were injured during the Blackout because they could not see in the darkness. Many people were injured tripping up, falling down steps, or bumping into things.