Willis Lamm's
Traffic Signal Collection

  Traffic Signal Visors

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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.

Some early visors were pretty much cylinders attached to the sides of traffic signals, cut into distinctive decorative patterns. These visors had no "pitch." In other words, they extended perfectly horizontally from the signal body. Shading from low angle sunlight was provided by the length of the visor and the design of the visor's shape.

While these visors produced adequate shading, the amount of visor necessary to prevent "phantom" illumination of signal lenses due to sunlight also made it difficult for pedestrians on street corners to see the indications of a single signal hanging in the center of the intersection.

"Flat pitched" visors.

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.

Yellow tunnel visors.
Other jurisdictions placed tunnel visors in front of both the red and yellow lenses with just the green lens visible to pedestrians.

Eventually as standards changed that required use of multiple signal heads for vehicular traffic and special pedestrian signals mounted on each street corner, the trend shifted from cap visors to tunnel visors as tunnels provided better shading and minimized side splash.

Additionally during WW-II a number of signals were equipped with tunnel visors under the theory that the signals would be better hidden from enemy aircraft and the enemy might not as easily identify metropolitan areas.

Where blowing snow could accumulate, tunnel visors typically were open along the bottom. In warmer climates full round visors were common.

A configuration once common in Baltimore.

Continue to Part Two

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