This is part four of an ongoing series on traffic signals. Part one and part two of the Spotters Guide were about how to identify the manufacturer, model, and approximate age of traffic signal equipment as seen in the Twin Cities. This then continued with the series originally titled “Traffic Signal Trivia” that went into a more in-depth, nationwide, and historical look of traffic signals. Part one looked at vehicle signals in general, Part two and part three looked at left turns.
Traffic signal companies have always been more in the business and sales rather than production, and thus most of the manufacturing was contracted out. This is especially true with lenses. Originally there were four major glass companies making lenses: Kopp, Corning, Macbeth-Evans, and Holophane. Macbeth-Evans, notable for it’s Depression Glass, was merged into Corning in 1936. Holophane eventually chose to concentrate on it’s much larger line of industrial light fixtures. Today Kopp Glass, founded in 1926 from the reorganization of the Pittsburgh Lamp, Brass and Glass Company is the primary manufacturer. Although there’s not much of a market for glass traffic signal lenses nowadays, Kopp still has the capability and will accept orders if someone wants a thousand of them.
Crouse Hinds “Command” lenses.
Early lenses sometimes had “Commands” printed on them. In the early days traffic signals were new and the position of the lights not uniform, so instructions as to what to do were seen as beneficial. These are rare nowadays and a set usually sells for over $300 on the collectors market.
Adler “Bar” Lenses
These were an attempt to accommodate the colorblind (in the days before the placement of colors was universal). There was a bar running across the lens- vertical for “go”, diagonal for “caution” and horizontal for “stop”. Although these didn’t catch on, the design can still be seen in today’s light rail signals. These were never common and are extremely rare today, a set of these usually fetches $1000 on the collectors market.
Kopp “Diamond Pattern” lenses (#27 and #44)
A common early pattern used by a number of manufacturers.
Holophane “Spiderweb” Lenses
In my personal opinion the most beautiful of lenses, collectors and enthusiasts refer to these as “Spiderwebs” due to the obvious resemblance. These were used exclusively on 1940s era GE signals. Siemens adapted these for Europe where they are very common, but in the US these, not lasting long and used by only one manufacturer, are somewhat rare. A set of these usually fetches over $300 on the collectors market.
Corning “Smiley Face” lenses (Type T and Type T-1)
Known as “Smiley Face” due to the distinctive pattern designed to throw light downward for the benefit of vehicles and pedestrians near the intersections when the signal was mounted on overhead wires. There was an earlier version with larger beads, but it was revised once ITE standards came out which regulated the light output of lenses. Although distinctive the later version isn’t especially rare, the CH “art deco” signals were extremely popular back in the day and as are desirable to collectors and thus many have been preserved when they’ve come down.
Macbeth “Butterfly” Lens
A very rare early lens, used some in Chicago.
Later Lenses (1940s to present)
Over time lenses evolved to be less unique. Most of these are still rather common and a set goes for less than $50 a set.
The T-3 was used mainly in later Crouse-Hinds signals, some of the later ones are (apparently) mis-labled as 1-3. There was also the T2, the “Faint Smiley” that maintained the ribbed outline of the original “Smileys” but not the beads.
Kopp “Brick” lenses (TL-4655 and TL-4955)
Following the “Spiderwebs”, GE again commissioned their own design with their own logo, commonly called the “Brick” pattern. This was later adopted by Econolite when they bought out GE’s signal business. All but the oldest GEs and all but the oldest and newest Econolites will have this pattern, including all in the time frame that they were used in the Twin Cities.
Kopp “Sawtooth” lenses. (TL-4677 and TL-4777)
Smaller manufactures would typically use “Sawtooth” lenses so they are extremely common in other areas of the country, but Minnesota has always shown a preference for Eagle and to a lesser extent Econolite, both of which used their own patterns.
Eagle Lenses (Kopp 88, 88.1, and 88A)
Very early Eagles would be equipped with #27 lenses, but Eagles own design, the Kopp 88 series, came in the 1940s and the same basic design was used by them until the end of the glass lens era. Although the pattern was not that distinctive, they featured Eagle’s logo and are by far the most common 8″ glass lens still in the area (often in the yellow sections of older Minneapolis signals).
With the coming of polycabonate signals came polycarbonate lenses (although aluminum signals could also be ordered with them, and polycarbonate signals could also be ordered with glass. These tended not to last, they’d oxidize in the weather, and get scorched when used with higher wattage bulbs that were on a lot, like main street greens or side street reds.
Glass and Polycarbonate Lenses
Like most collectors and enthusiasts I have little interest in 12″ lenses. There isn’t anywhere close to the same variety of the earlier, more interesting 8″ lenses, and 12″ signals are awkwardly large for indoor display. But here are a few of them that I have laying around, a new 12″ Lexalite red, a Eagle branded polycarbonate yellow, and a generic glass green from Poland.
Lenses for the 3M Model 131 signals were square plastic with a Fresnel pattern. Balls or arrows were stenciled out.
Earlier LED Modules
The first LED modules were actually designed to utilize existing sockets, reflectors, and lenses, and were initially available in red only. the primary companies making them were Electro-Techs, Ecolux (later bought by GE), Cooper (which was popular in New York but exited the business, Dialight, Leotek, EOI, and Swarco.
The earlier modules all had the individual LEDs exposed, this is from Leotek. Dialight and Cooper were arranged in circles rather than rows.
These were an attempt to compete with the later emerging “Incandescent Look” or “Uniform Look” designs while using the older technology of arrays of many low-power LEDs by putting a diffuser lens on top to spread the light. There’s a lot of these in the Twin Cities, but they have not held up well, are now reaching the end of their life with many partial failures, and tend not to be liked by collectors.
Ecolux / GE “Honeycomb”
These were a variation of the exposed LED modules with a small magnifying lens over each LED. There are a number of these still in Minneapolis and St. Paul and they tend to outlast even the newer RX-11s.
Later LED Modules
The first of the “Incandescent Look” LED modules, Dialight and Leotek both produced models that were a throwback to the early diamond pattern lenses. These are impossible to distinguish from each other in the field.
Later Incandescent Look
The later GE, Dialight, Leotek, and EOI modules are very similar and are difficult for even collectors and enthusiasts to differentiate in the field. Swarco LEDs, used some by Minneapolis and to a lesser extend by other agencies, are different with a noticable brighter spot in the center.
Also interesting is that the US has switched to incandescent look modules almost exclusively, while LED look remain common in other countries. Incandescent look modules are much deeper than LED look, almost as much as the old incandescent reflectors. Other countries have adapted traffic signals that are much shallower, and can only accommodate LED look modules.
Several companies make LEDs to retrofit 3M and McCain Programmable Visibility signals. Like all traffic signal LEDs these are not dimmable, so a retrofitted signal can be rather bright at night, and if a tech forgets to remove or disable the dimmer the LED module will flicker horrible and eventually burn out.
Future articles will deal with pedestrian signals and controllers.
On the close-up of the Honeycomb, it looks like there is a mixture of green and blue LEDs–is this the case?
Two different shades of green- “Emerald Green” and “True Green”, apparently they mixed them to get the shade they wanted.
Will you (eventually) cover the different methods for blocking signals at skewed intersections? I think the different concave methods vs. shielding vs. full circles could be a very interesting post… maybe it’s because I just want to do the physics of it, but still.
I somewhat covered Programmable Visibility signals in part 2 of the “Spotter’s Guide”, the other method being to use a full circle visor with louvers. I fear as I get more and more into this the interest the average reader has is going down. Current plan if all goes well is to do two articles on pedestrian signals and one on controllers and then I’m about out of ideas for this series.