Willis Lamm's
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Traffic Signal Visors |
The first traffic signals were for the most part boxes with electric lamps inside that projected through Fresnel railroad signal lenses. It soon became evident that a signaling system that worked fine when focused on a specific railroad track was less than adequate in the more dymnamic environment of city streets. Early signal developers soon designed improved lenses that were specifically designed for highway use and they had to develop some kind of shading system for the lenses. These shades were known as visors.
Since many intersections had only one signal controlling them, the visors had to limit glare from reflected sunlight but at the same time allow vehicles in multiple lanes and pedestrians an unobstructed view of the signal's lenses. |
Visors on a 1920s vintage AGA signal.
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Signal designers eventually figured out that pitching visors at a slight downward angle provided nearly equal shading from low angle sunlight, but allowed for a smaller visor that provided a wider view of the signal's indications by motorists and pedestrians.
This visor style became known as the "ball cap" visor, later shortened to "cap" visor. The early ball cap visor was the precursor to what was eventually the most popular visor style used until the late 1960s. |
"Ball cap" visors. |
Many cities had buildings with residential apartments on the floors above ground floor businesses. These apartments were often about equal to the level of span wire mounted traffic signals. In some instances the signals, especially the yellow lights, could be disturbing to residents. Cylindrical tunnel visors were often provided to cut down on "side splash" light.
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Yellow tunnel visors. |