A brief guide to the blackout lighting regulations for civilian vehicles during World War 2 in Great Britain.

I have attempted to document the evolution of the vehicle lighting regulations as they changed during the course of the war. Most of the information being compiled from contempory photographs, newspapers, motoring magazines and the original police notices.


Some background

Even though war was declared on the 3rd September 1939, the blackout was introduced a couple of days earlier on the 1st September. The importance of removing ground light sources was first recognised during the Zeppelin raids on Britain during the 1914-1918 war. Any lights on the ground can provide vital navigation clues for enemy bombers intent on locating their targets. During the years preceding the Second world war, conflict seemed inevitable and ARP plans were being made, including the need for a total nationwide nightly blackout. During 1939, trials were conducted by the RAF, with selected towns attempting to maintain a blackout. One of the major risks was identified as the lights on vehicles.

All the wartime lighting regulations are based around the earlier "Road Transport Lighting Act 1927", which classifies the light by two types.

  • The first are the obligatory lights, these are the lights which show the position and extremes of the vehicle to other road users. The two sidelights show a white light to the front on the outer edges. The rear lights show a red light to the rear, as a minimum, one near the offside only. From behind, the true width of the car was indicated to other road users by two red reflectors close to the edges
  • The second type of lights are those to provide illumination to allow the driver to see where they are going. In the main these are the headlights, but could also describe spotlights and foglights.

In some cars and most motorcycles these two types of light were combined into one.

A most important thing to remember is that cars only needed to conform to any blackout regulations if they were used during the hours of darkness.

For the purpose of enforcing the regulations, the definition of hours of darkness was given as "During summer-time, the time between one hour after sunset and one hour before sunrise, and during the rest of the year, the time between half an hour after sunset and half an hour before sunrise."

The first police notice - September 1939

Given all the preparations during the preceding years, the first month of the war seems very confused. When the first police lighting order was published it appears very "Make do and mend". The measures outlined to control the output of the lights involved homemade shrouded masks and instructions to paint reflectors black.Both headlights were to be masked and used. The front of the headlights were blanked off except for a narrow 3/8" horizontal slot just below the lamp centre line. A projecting shroud then covered the slot.

The basic form of the first mask

Sidelights and rear red lights (ie. the obligatory lights) if bigger than 2" diameter or equivalent area, to be "partially masked by reducing, by means of an opaque screen,the aperture throughwhich light is emitted to a circle of 2-in. diameter or equivalent area"

Rear stop lights were to be reduced to an area of one square inch maximum. In most cases the stop and rearlight were combined so the smaller aperture of 1" took precedent.

The following were introduced at the start of the war and did not return to normal until the end of regulations.

  • Reversing lights (uncommon on cars of this period) not permitted
  • Lights illuminating the rear registration plate not permitted
  • All other windows or side panels in light units to be completely obscured
  • Matt white paint applied to the edges of wings, edges of the running boards, and to the bumpers - this seems to be often ignored
  • Internal lights not permitted
  • Directional indicators (most of which would of been of the fold-out trafficator type), if fitted and used, to be masked so the light is only visible through a slot an eigth of an inch wide, or an arrow comprising of three lines each an eigth of an inch wide.

New "homemade" masking - mid September 1939

A couple of weeks into the war, an alternative headlight masking was announced by the government. Only the nearside headlight was to be masked and used, the offside was just to have the bulb removed. The mask was described as "an opaque cardboard disc covering the whole area of the glass except for a semi-circular aperture 2 ins. in diameter with the base uppermost, the centre of the base coinciding with the centre of the lamp". It was also necessary to paint black the lower half of the reflector in the masked nearside light. Whilst car owners were encouraged to use this method, it was still allowed to use masking to the first regulations if prefered.

Specifying the permitted light output

It was almost a month into the war, at the end of September that the Government announced a proper specification for the amount of light that could be emitted by a car. The headlight was to be masked such that the beam did not go above the horizontal and struck the ground in front of the car at a distance five times the height of the headlight and having an intensity not more than 2.5ft candles at that distance.
In order for the motorist to meet this specification, a headlight mask was designed by the government.

The introduction of the three slot mask - September to November 1939

It was at the end of September that the Government released the design details of the three slot mask. They were to be made by any company that wanted to. This mask was to be compulsory on the offside headlight only, from 21st October. Due to delays with raw materials and manufacture, this date was put back to the end of November.

By the end of November supplies of the new mask were still restricted and the date by which they became compulsory was put back indefinitely. Also at the end of November the Government changed it's mind on enforcing which side of the vehicle the mask was to be mounted. To quote The Times newspaper of November 22nd 1939 -

“In the provisions published on October 4 it was stated that a vehicle having two headlamps must have the mask fitted to the offside headlamp, but this has been amended to allow the mask to be fitted to either headlamp, in order to focus the nearside light on the kerb in towns and the offside lamp on the white lines in the centre of country roads.”

For the following few months the letters pages of the motoring press began to fill up with the debate as to which was the best side to mask. It ended up splitting the opinion into town versus country. Those using cars in the towns favoured the nearside, illuminating the kerb. Country dwellers preferred the offside, with the light falling to the centre of the road. It must be remembered at this point in the war you could only mask and use one headlight. So whichever side you took, you were commited to keeping your mask on that light only.

The basic dimensions of the Regulation mask

The new mask replaced the front glass of the headlight. On some cars, such as those with headlights built in to the wings, the shape and curve of the glass did not permit the fitting of the new regulation mask. In this case a seperate additional headlight with the mask fitted was allowed.

The pattern mask is now compulsory- January 1940

After many months of dawdling, the use of an approved three slot mask finally became compulsory on 22nd January 1940. The use of the earlier masking arrangements became illegal on this day.

Fitting a second pattern mask - February 1940

On the 10th February the government announced that a second pattern mask could be fitted on the redundant headlamp. But both lights were prohibited from being lit at the same time. The car wiring needed to be altered to allow for a changeover switch so that the lit side could be changed without both lights being lit. The fitting of a second mask was never compulsory and if the single mask suited you, you were free to carry on with just one. It is worth emphaising that all changes to the headlight regulations from this time are best considered as allowed improvements, and if you wanted to continue following the earlier rules (from the introduction of masks, Jan 1940), that was acceptable.

Other "non-pattern" masks allowed - March 1940

At the beginning of March 1940, the government allowed for manufacturers to produce their own designs of mask, as an improvement on the three slot type. These non-pattern masks still had to fulfill the basic specification of light intensity emitted (not greater than 2.5 foot candles at ten foot).

From this point in the war, if two masks were fitted, they did not need to be of identical design, so long as each meets the government specification

Second headlight may be used for identity purposes - End March 1940

For vehicles engaged in official duties a set of identity letters were agreed upon. From the end of March it was possible to use a cutout mask to display the relevant lettering on the second headlight. The intensity of the displayed light was to be the same as a sidelight would emit. The original set of letters which could be displayed on the second light are as follows -

Wair raid Warden
FAPFirst Aid parties
DCDecontamination Squad
RP/RRepair Party - Roads
RP/WRepair Party - Water
RP/ERepair Party - Electricity
RP/GRepair Party - Gas
SPStretcher Party

During the rest of the war this list was added to, so that by the end of war the extra following letters were also allowed.

A/CARAmbulance (Vehicles for sitting cases)
BTSBlood transfusion Service
ARPDirecting staff
GCUGas Cleansing Units, Mobile
GISGas Identification
LRLight Rescue
RRescue or Heavy Rescue
GPOTelecommunications (G.P.O.)

It is worth noting that the letters are similar to those found on Mk2 "Tommy" helmets issued to Home front services.

The cutting on the right is from a "Practical Motorist" magazine dated 23rd March 1940

The reduction of permitted sidelight area - October 1940

In October 1940, the regulations were changed to decrease the area of sidelight from 2"diameter to 1"diameter (or their equivalent areas). This was to remain in force till the end of the lighting regulations.

As commonly mentioned in the press of the day, a quick check for the new smaller area, was to compare it with a halfpenny coin, which had a diameter of exactly 1".

Both lamps lit - End of September 1941

For motorists who had fitted masks to both headlights, it was now permitted to have both switched on at the same time. The regulations did not change from this point till the easing of regulations towards the end of the of the war. One masked headlight was still allowed for those that preferred it, on either light. All this is summed up in the 31rd edition of "The Motor Manual" published May 1942, quoted below-

“Two masks can be fitted and the use of both lights is recommended. The masks can be of the prescribed three-slot type made in accordance with official recommendations, or single or multi-slot proprietary types or, indeed, of any other design so long as it fulfils the specification laid down by the the law – viz., that the intensity of the beam must not exceed 2˝ ft. candles at a distance of 10 ft. from the car; the light must not strike the road nearer than 10 ft. from the car, nor must it rise from the horizontal. Should only one mask be used it is best that it should be on the off side. One could fit an entirely separate lamp to which the mask can be fitted.”

"Dim-out" and the end of regulations - September to December 1944

The Germans had started to use the pilotless V1 rocket in the summer of 1944, to be followed by the more powerful V2. There was no longer a risk from piloted bombers. The goverment began to relax the blackout regulations for householders and street lighting in September 1944. This period of the war was termed the "dim-out". The only change to vehicle lights was to allow sidelights to increase to their original areas. It was on the 24th December that the government announced (with immediate effect) that the lighting regulations for vehicles no longer needed to be followed. Motorists were reminded "that masks should be kept ready in case a change in the position calls for the restrictions to be reimposed". Manufacturers of headlight rims and glass anticipated a sudden demand to replace those parts misplaced from the start of the war.

Anything goes - a mixed bunch of cars, all with differing styles of blackout precautions. The scene is at the carpark of the Derby 1941 which was held at Newmarket instead of Espom during the war

A brief note on motorcycles

Although many masks were marketed as if different from those supplied for cars, no special masks were made specifically for motorcycles.

As far as I am aware all motorcycles of the period had their obligatory lights in the form of a pilot bulb built into the main headlight reflector. All these motorcycles would have used versions of the masks available with an opaque aperture (the "dual purpose" type). The masks used on motorcycles were subject to all the same changes as those for cars during the progression of the war.

Click here to see some examples
Click here to get further details on specific mask types