3M
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Contents
3M Brand
From 1969 to 2007, 3M produced signals and adapters designed to enhance signal visibility to both drivers and pedestrians. Their most iconic and well-known product is the M-131.
Products
Full Signals
Vehicle Signals (12")
M-123 Programmable Visibility Prototype Signal
The M-123 was the first traffic signals ever made by 3M. They were most likely made a few years before 1969. It's original purpose was to have "high visibility"; more fully-lit and easier-to-see indications. It could also be used for "programmable visibility", which means the viewing area of the signal can be limited down to single lane.
This signal was a prototype. It is known as an early version of the M-131. The M-131 signals are nearly identical to these; 3M sold them to cities that liked the idea and wanted to test them out. 3M tested them and made improvements as they saw fit. Finally, 3M released their final product as the all-new M-131 signal and began expanding their product line.
The main visible difference is that the rear lamp door/housing was cone-shaped, unlike the M-131's more faceted version The M-123's doors had the 2 hinges on top and the 2 wingnuts on the bottom instead of on either side. M-123s didn't have latches to secure the lenses, so they were prone to falling out if the door was opened. Finally, they were sand-casted, and somewhat heavier than M-131s.
Lenses
These were available with the following lenses:
- Red Ball
- Yellow Ball
- Green Ball
- Green Arrow
M-131 Programmable Visibility Signal
Overview
3M, the same company that makes well-known everyday products such as Scotch tape, entered the traffic control industry in 1969 with High-Visibility signals. These lights were unlike any other at the time in both design and operation. The most noticeable features are the square lenses and futuristic-looking housing. The also had special capabilities, such as High Visibility (giving a fuller, clearer indication) and, most notably, Programmable Visibility (being able to limit the viewing area to as little as a single lane). After modifying the M-123 prototype signal, 3M released this signal line in 1969 and produced them until 2007 with only a few changes.
Construction
Front Door
The front door was always flat-black in color from the factory. The door itself was a simple square ring with screw-holes for the visor, hinges, and an inset for the lens to fit in. The weather-tight seal was produced by the lens gasket itself, sitting in the door. --To Be Edited--
Back Door
The back door held the bulb socket and basic wiring, including the plug for electrical connections. In earlier models, only two connections were made (the bulb only uses two of the three prongs) for the circuit, but in later models, three wires were used, the middle connection for a larger-wattage resistor for the dimmer. Opening the back door also gives access to the diffuser lens and back of the masking lens, which is used to mask off areas where drivers shouldn't see the signal. --To Be Edited--
Main Housing
The main housing contains the dimmer, light shield, wire terminals, and access to the masking lens. --To Be Edited--
Some design issues were changed over the course of production. An incomplete list includes:
- Dimmer - The dimmer and associated wiring was changed to support a larger-wattage resistor, housed in the back door. The dimmer, PCD-111 was changed to a PCD-111A.
- Cast Mold - The mold for the housing was changed a few times, and included changing the corners (around the hinges) and support ridges. The back door was changed to show 3M's new logo as well.
Diffuser Collar - The aluminum collar around the diffuser lens was originally taller, but after early production was shortened. --To Be Edited--
Uses/Advantages
PROGRAMMABLE VISIBILITY
- Viewing Area Limiting
With PV signals, you can limit the viewing area to anywhere from one approach at an intersection to a single lane at that approach. This is ideal for skewed intersections, where you could see the traffic signals of a different approach; turn signals, that cycle independently and might distract through traffic; divided intersections, where some lanes are signalized while others aren't; ramp metering, where each lane's signal cycles independently; and signals for bus/transit lanes, that might confuse vehicle traffic.
This is accomplished by applying optical masking tape to one or both sides of the diffusing lenses. The light only shines through the remaining uncovered portion,, and from that angle the front lens appears to be fully lit. When looking at the angle of the covered portion, it appears to be very dimly or not-at-all lit.
- Viewing Distance Limiting
Another feature of these signals is the ability to limit the distance of the visibility. This is ideal for multiple intersections that are very close to each other. Drivers might look ahead and see signals showing green at the wrong intersection, which can cause confusion and accidents.
Distance limiting is accomplished by applying optical masking tape to the top of the diffusing lens. The light only shines through the bottom uncovered portion, so from close up the front lens appears to be fully lit. When looking at the signal from further away, it appears to be very dimly or not-at-all lit.
HIGH VISIBILITY
- Fuller Indication
The 3M PV signal is also made to have fuller, clearer indications. Because of the special diffusing lens inside and the fresnel pattern on the external lens, the lens appears to be fully and evenly lit. There is no bulb "hot spot" on the lens. And since the whole lens is lit at its brightest, it can be seen much better, and from further away (within the programmed visibility limits!).
- No Sun Phantoming
Sun phantoming is a condition with traffic signals where the sun shines in through the lens, reflects of the reflectors and shines back out the lens, making all indications appear to be lit even when they aren't. This can be a serious problem at large intersections. Because it would have to go through 4 lenses (including the cover of the PAR 46 bulb), into the bulb's small reflector and back out, there is little opportunity for that to happen.
Disadvantages
- 3M signals were far more expensive than regular traffic signals. To achieve visibility limiting, many places opted to simply attach louvers on their existing signals. Though they couldn't limit the visibility as extensively, and they also block some of the light output even for the direction they face.
- 3M signals used PAR 46 bulbs, similar to those used in flood lights. They have shorter lives, higher temperatures, and are considerably more expensive than regular light bulbs.
- 3M signals were also heavy; a 3-section 3M weighs around 65 pounds, 15 heavier than a typical traffic light. This made installation difficult. 3M made it slightly better by having a terminal block in every section instead of just one, so they could wire it it out through any section depending on how they are installed.
- And, while 3M was the first to create such a signal, in more recent years (as early as 1997) they have had some competition. McCain Traffic and Intelight (previously OptiSoft) both make programmable visibility signals.
The McCain PV Signal was developed in early 2000s, and is nearly identical in design to 3M PV signals. Many parts are interchangeable with the M-131 as well, including the Light Shield, Diffusing Lens, Masking Lens, Bulbs (LED or Incandescent), and Wire Terminals. McCain's PV signals use round lenses (overcoming one of the drawbacks to 3M's square lenses) and they use standard 12" visors which makes them easier to replace.
Intelight signals are very different in design but utilize the latest LED technology, which makes far better in that regard.
This competition is part of the reason behind declining sales which led to 3M dropping out of the traffic signal industry in 2007.
Lenses
The lenses on a 3M are unique in that they are square. They glass has a frensel pattern, which 'enlarges' the view to the driver, effectively enlarging the point of the visible mask/diffuser lens to the driver. Lenses are made of 2 parts: the colored glass piece, and the black mask. This mask was printed on the inside, outside, or on both sides of the lens, and determined what shape was illuminated. Also unlike typical lenses, these could be rotated (in increments of 90°, of course) as needed. Older lenses were formed and have round corners, while newer lenses were made completely square and then had the corners trimmed off. All lenses had a number stamped onto the outer side, possibly a production run number, while they also had one on the inner side, possibly showing part number or revision of the fresnel design.
Here is the list of known lenses for M-131 signals:
| Standard | Special |
Balls
Arrows (90°; Left, Right, or Upwards)
Diagonal Arrows (45°; Diagonal Leftward or Diagonal Rightward)
|
Light Rail Symbols
Canadian Shapes
Special Worded
|
Serial Numbers
All 3M signals were given a serial number. A small decal, about 1" x 2" in size, was placed on the back of the housing inside the back door. A serial number was stamped onto this decal. Many lights were given sequential numbers for each head - i.e. Red would be "100", Yellow then "101", and Green "102". There were at least four versions of the decal, with the two common being known as the 'Old Style' and 'New Style'.
A list of known serial numbers owned by collectors can be found here.
M-131R Bimodal (Ball/Arrow) Signal
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M-133 Dual-Indication (Green/Yellow) Signal
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Pedestrian Signals (12")
M-131 P.V. Pedestrian Signal
This M-131 PV pedestrian signal is exactly the same as the M-131 signal, except with different lenses.
Lenses
The following lenses were available for these signals:
- Portland Orange HAND Symbol
- Lunar White MAN Symbol
- Portland Orange "DONT WALK"
- Lunar White "WALK"
- Red "DONT WALK"
- Green "WALK"
M-132 Dynamic Pedestrian Signal
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Signal Adapters/Converters
Vehicle Signal Adapter (8")
SA-130A (Adapter attachment)
3M never made full 8" traffic signals; however, they did make programmable visibility attachments that can be put on any normal 8" housing. They are mounted in the door, taking the place of the lens & visor, but it utilizes the existing reflector and bulb. A page showing how these attachments are installed can be found here.
The interior of these attachments is similar to that of 3M's 12" signals. It has a regular lens at the outside end, and a diffusing lens on the inside end. Unlike the 12" signals, though, there is no optical limiter lens (a clear lens where the optical masking tape is applied to limit the area of visibility), so the optical masking tape is put directly on the diffusing lens. It still works in the same way. Finally, on the end of these adapters, a small visor is attached. Without the visor, these adapters are about the same size as normal tunnel visors.
Lenses
- Red Ball
- Yellow Ball
- Green Ball
- Green Arrow
(Though they may have been a special order option, no yellow or red arrows are known to have existed.)
Vehicle Signal Converter (12")
M-150 (Lens/Reflector System)
The 3M M-150 Lens & Reflector System was created by 3M to give regular 12" traffic signals some of the M-131 signal's features.
The M-150 is installed almost exactly like a modern LED module. The signal's original socket, reflectors & lens would be removed; the M-150 unit has all of those in it. The wires that went to the original socket are rewired to the back of the unit. It is then fitted into the door just like the lens was.
The front extended part is a dual diffusing lens (dome-shaped on the inside, cylinder-shaped on the outside). These inserts offered the High Visibility feature of the M-131 signal (having a fuller, brighter & clearer indication, compared to that of a typical incandescent signal). It did not have the Programmable Visibility feature, because the masking would have to be applied too close to the light source to have the proper effect. These were available in green, yellow, and red balls, and likely all color arrows as well.
DISCONTINUATION:
3M discontinued these early on, because they caused an effect called 'sun phantoming', which occurs when the sun shines through the lens and is reflected back out by the reflector, making it look like all indications are lit.
PC-310 Signal Intensity Control
Nothing is known about this device.
Signal Enlargers
Signal enlarges are attachments mounted on a signal door that expand to fit a larger lens. Around the early 60s, larger signal indications were becoming more popular because visibility was becoming a greater concern. Installing enlargers on a signal was cheaper and easier than replacing it.
3M made 3 lines of signal enlargers; for vehicle signals, round-lens pedestrian signals, and square-lens pedestrian signals. They were all reprimanded for not being built to 3M's strength & quality standards; they were made of thin, lightweight folded sheetmetal with many unsealsed slots on the corners and along the sides. They were mounted in the place of a signal's visor, using the exact same attachments.
Vehicle Signal to Vehicle Signal
These were made to convert the display of typical 8" signals to that of a 12" signal.
SA-812
Patented on December 17 1973, this enlarger unit converts a typical 8" signal indication to a 12" indication. The enlarger mounts where the visor would go on the signal's door. It is essentially a box that expands around an 8-inch lens to fit a door with a 12-inch lens.
The signal's original 8-inch lens is replaced with a glass diffusing lens. The enlarger is attached in the place of the visor using the visor's screws. It is octagon-shaped where it attaches to the door; as it extends outward, the slanted sides (which are triangle-shaped) become the corners of the square-shaped front. A square lens slides into the lens holder/front door of the unit, which has a 12" circular hole for the indication to shine through. The door then simply slides into place on the front of the enlarger.
With this setup, the light shines through the 8" lens, into the enlarger and out the 12" lens, generating a larger and more visible indication with the same amount of light and without having to replace the signal.
3M specifically noted that these enlargers would not fit Eagle Durasig signals or any TSI signals. They offered special clips needed when mounting on Crouse-Hinds signals.
The name of this product means "Signal Adaptor - 8 inch to 12 inch"
SA-810
If enlargers need to be used on two consecutive sections of a signal (for example, the 2 green indications on a 4-section R–Y–G–GA signal), there would not be enough space. The SA-812 12" enlarger extends slightly over both sections around it in order to... well, enlarge... and you would not be able to fit a second one beneath it.
That is what the SA-810 is for; it is designed specifically to fit under an SA-812. It is almost exactly the same as the SA-812, except that it bends down at the top (instead of up) to fit beneath and match the curvature of the other one. Because of the height limitation, the lens is only 10"x12". And due to that irregular size, they were only available with green left or right arrows. Horizontal arrows are the only indications that would be able to fit while remaining the correct size.
The name of this product means "Signal Adaptor - 8 inch to 10 inch"
Vehicle Signal to Pedestrian Signal
Though the 3M catalog specifically says these "are adapters to enlarge 8" vehicle signals to 12" pedestrian signals", they were most likely designed for round-lens WAIT-WALK pedestrian signals (which used the same housing as vehicle signals).
SA-812DW
This enlarger uses the same body as the SA-812 with the lens & door of a SA-912.
The name of this product means "Signal Adapter - 8 inch to 12 inch pedestrian, DONT WALK"
SA-810W
This enlarger uses the same body as the SA-810 with the lens & door of a SA-910.
The name of this product means "Signal Adapter - 8 inch to 12 inch pedestrian, WALK"
Pedestrian Signal to Pedestrian Signal
If you notice, this image has 2 mistakes; the dotted signal behind it is a vehicle signal (instead of a pedestrian signal), and the back of the enlarger has an octagon shape (instead of square).
The signal has since been removed.
These were made to convert the display of typical 9" pedestrian signals to that of a 12" pedestrian signal.
SA-912
This enlarger is for the DONT WALK section of a pedestrian signal. The SA-910 is for the WALK section.
The enlarger mounts where the visor would go on the signal's door. It is essentially a box that expands around a 9-inch lens to fit a door with a 12-inch lens.
The signal's original 9-inch lens is replaced with a clear or colored plastic diffusing lens. The enlarger is attached in the place of the visor using the visor's screws. It is square-shaped at both ends. A square DONT WALK plastic frensel lens with red 4½" lettering slides into the lens holder/front door of the unit, which acts as a frame for the lens. There is a lip around the inside edge of the door frame, to which the new visor attaches. The door then simply slides into place on the front of the enlarger.
With this setup, the light shines through the diffusing lens, into the enlarger and out the 12" lens, generating a larger and more visible indication with the same amount of light and without having to replace the pedestrian signal.
3M offered specific versions of these adaptors with slightly different attachments to fit Marbelite and Econolite pedestrian signals.
The name of this product means "Signal Adaptor - 9 inch to 12 inch"
SA-910
This enlarger is for the WALK section of a pedestrian signal. The SA-912 is for the DONT WALK section.
This enlarger section has a 10"x12" lens. It is smaller because it needs to fit beneath the SA-912 adaptor on a pedestrian signal. The SA-912 (DONT WALK), which is a full 12"x12", extends slightly over the WALK section. In order to match the curvature, the top of this adaptor bends downward, instead of upward like the SA-912. Other than that, they are exactly the same.
The DONT WALK indication needs to be largest because it has two lines of text, and the WALK indication only has one. In a normal signal, the DONT WALK and WALK lenses are the same size, and the WALK has blank space on the top and bottom. That extra space could be cut off and the WALK indication would remain the correct size, which is essentially what was done with these.
Like the SA-912, this adaptor is attached where the visor would go on a signal, using the visors screws. The original lens is replaced with a clear or colored plastic diffusing lens. The outer lens, a plastic frensel lens that says WALK in 4½" white lettering, is displayed on the front of the adaptor.
The name of this product means "Signal Adaptor - 9 inch to 10 inch"
Signs
Reflective
3M is a leader in the industry of reflective signage and sheeting, in addition to many other road products. You can see them here: http://solutions.3m.com/wps/portal/3M/en_US/NA_roadway/safety/productcatalog/~/Roadway-Safety?N=3293989410+7566298+7584153+8695783+8694413&rt=r3
Electronic
3M made a bi-modal, time-programmable sign lighted sign for roadways. Little is known about them.
