24h Le Mans
24 HOURS CENTENARY – PERPETUAL INNOVATION ⎮ Among the many technical innovations developed and/or unveiled at Le Mans, fog lights made their first appearance very shortly after the first running of the race.
For the 4th 24 Hours of Le Mans in 1926, Pierre Marchal – founder of the Société Marchal pour la fabrication de lanternes et projecteurs (Marchal company for the manufacture of lanterns and headlights) – convinced engineers for the previous year's winner, a Lorraine Dietrich, to install an additional headlight in the centre of the car to improve visibility in fog.
It is common for fog to settle during the night and at dawn over certain more humid areas of the track, such as Mulsanne and Maison Blanche. Given the speed at which the cars travel, a clear view from afar is a must.
Conventional headlights emit a relatively high light so the beam reaches as far as possible. As a driver passes through fog, water droplets that reflect each other, a halo forms that drastically reduces visibility. Everyone has experienced this problem when driving with full headlights in the fog. Changing to dipped headlights, whose beam is lower, avoids this glare effect. The layer of moisture is located just a few centimeters above the ground, so fog lights are designed to project a beam below this layer to avoid refraction. Thanks to the unique shape of the lens (with vertical streaks) associated with a reflector favouring width and directed downwards, the beam becomes wider and illuminates the edges of the road more effectively.
During the night and early morning at the 1926 24 Hours, fog lights gave the Lorraine Dietrichs the advantage and made possible the first-ever hat trick for a French constructor, against the Bentleys (collective accident in the night at…Maison Blanche due to lack of visibility) and Peugeots (disqualified).
Unsurprisingly, more and more cars were fitted with fog lights in subsequent years. The main headlights were then housed on either side of very high grilles, above the front fenders, which themselves had to allow for large diameter wheels. A third fog light, placed lower in the centre of or below the grille, became widespread during the 1930s. In 1933, Alfa Romeo won the race with a pair of fog lights located below the main headlights.
This innovation that had first been tested at the 24 Hours circuit soon became standard on production cars. After World War II, fog lights could be found on everything from the winning Ferrari at Le Mans to a Renault 4CV or Peugeot 203 (an optional feature) on regional roads. Parts suppliers at the time made a mint selling fog lights to the owners of unequipped cars.
One-piece streamlined bodywork that included the wheels (separate fenders were prohibited) was permitted by the ACO regulations beginning in 1952. Single and paired headlights were allowed in the centre or to one side, afixed to the nose or grille of the car. Over time, fog lights became more streamlined and better integrated into front bonnets or fenders.
In the second half of the 1960s, it was common to see long-range headlights and fog lights on a car's two spoilers. In the 1970s and thereafter, the streaks on the glass lens of fog lights were done away with, allowing for broadening of the beam that illuminated the roadside, so fog lights served a dual purpose as cornering lights as well.
LED headlights now make it possible to achieve high-performance lighting whatever the situation by varying the number and orientation of the LEDs lit. There is no longer any specific optic for fog and the same is true on production cars.
Last but not least: rear fog lights, activated the moment rain hits the track. The spray of fine water droplets trailing cars equipped with massive tyres amounts to the same lack of visibility as fog. Installed in the back centre of the car, a rear fog light allows a driver to gauge more accurately his/her distance from the car in front. First seen in the 1970s and mandatory on vehicles since 1990, it was originally a simple red light, fitted with a bulb twice as strong as the rear lights. It too has since been updated to LED technology...and Brits rightly call it the anti-crash light!
PHOTOS (Copyright - ACO Archives): LE MANS (SARTHE, FRANCE), CIRCUIT DES 24 HEURES, 24 HOURS OF LE MANS. From top to bottom: two fog light pioneers, the winning Lorraine Dietrich (centre) in 1927 and the winning Alfa Romeo of Tazio Nuvolari/Raymond Sommer in 1933; above, LED night lighting on the winning Audi in 2013.
