A Spotter’s Guide to Traffic Signals, Part 1

Ever look at a traffic signal and wonder how old it is or who make them?  What follows is a two part “spotter’s guide” to the traffic signals of Minnesota. There is a certain slang used by people that are used by enthusiasts and collectors of traffic signals. I’ve included it here since it’s useful to describe and distinguish various models, in all cases it’s enclosed in parenthesis to make it clear that it is not official terminology. Now onto the guide:

Eaglelux KB63 “Tall Fin” and “Short Fin”

The Eagle Signal company is one of of the oldest of the signal companies, located in the Quad Cities for many years. And the oldest signals still in place in Minneapolis are the Eagleluxes, which was the original Eagle trade name for their signals. (This area has long shown a strong preference for their equipment).  Although a lot have been discarded in the recent traffic signal timing project, there still are some left, many with incandescent yellow. The most distinguishing feature of them is the art-deco like fins on the top and bottom plate. (Early sectional signals had open tops and bottom to each segment, there’s be an end plate on each end and tie rods holding the entire thing together.)

These were made from the 1930s to the mid-1950s. Early KB63s, the “Tall Fin” have a brass ID tag (normally covered by years of paint) on the bottom plate and no logo on the backs. Later there were running production changes where the fins were noticeably shortened, the Eagle logo was added to the back, and the ID plate was removed, and the fins were noticeably shortened The reason for this is speculated to be that the long fins interfered with more modern mounting hardware that was coming into use. This  configuration is known to enthusiasts as the “Short Fin”.

Eaglelux "Tall Fin", Minnehaha Ave. and 46th St, MInneapolis.

Eaglelux “Tall Fin”, Minnehaha Ave. and 46th St, MInneapolis.


Eaglelux "Short Fins", Minnehaha Parkway and 50th, MInneapolis

Eaglelux “Short Fins”, Minnehaha Parkway and 50th, MInneapolis

Eaglelux backs. This is a mix of early (no logo) and late (with logo) sections and late (short fins) top and bottom plates

Eaglelux backs. This is a mix of early (no logo) and late (with logo) sections and late (short fins) top and bottom plates

Eagle  “Rodded Flatback”

In the mid 1950s, Eagle dropped the Eaglelux name and introduced the “Rodded Flatback”. This was somewhat of a transition that was only in production for a few years. It introduced the simplified body style that would last for many years, but maintained the use of top and bottom plates, (now with no fins) with tie rods and the older style “slam latch” reflectors, and old small logo.  I don’t know of any that are in the field, but list it as there might be, and since it is interesting as a transition to the more modern style. Also of note this is the first that had dedicated 9” square pedestrian housings. Before if you wanted pedestrian indications you added a 4th sections to the vehicle section and installed a black and white circular “Walk” lens, or later on a separate 2-light signal with an orange “Wait” and white “Walk”.


Eagle “Rodded Flatbacks”. From my personal collection

Eagle KB170 / KB380 “Flatback”

In 1960 Eagle introduced this model,   Gone are the tie rods and plates, all sections now have tops and bottoms and are held in place by internal clamps, and the reflector was a modern “H” shape.  The small Eagle logo was replaced with a much larger version. The initial production had a large trapezoid above and below the eagle, enthusiasts call these these “Trapezoid Flatbacks” and only they only lasted a few years before the trapezoids were removed (the reason for them is not known).

Eagle "Trapezoid Flatback", W 7th St, St. Paul

Eagle “Trapezoid Flatback”, W 7th St, St. Paul. This is the only one I’ve seen in the field.

Although the 8″ variety are most common, in the 1950s 12” indications were introduced and promoted by the signal companies as being more visible on the newer higher speed roads and more complicated intersections. Initially only the reds were 12”, and only on overhead mountings (which became increasingly common during that time)- 8” and 12” sections have always been able to fit together. Later all three sections were 12” (and now 8” are only allowed on lower speed roads). Eagle’s version was designated model KB380 and besides the obvious size difference looks similar to the 8”. Some KB380s are found on older installations in Minneapolis and the suburbs, but they are not overly common.


Eagle "Flatback" front and internals. Virtually all traffic signals still have a similar design. From my personal collection.

Eagle “Flatback” front and internals. Virtually all traffic signals still have a similar design. From my personal collection.

Eagle AluSig and DuraSig

In the early 1970s there was a radical redesign. With catchy trade names came a move to internal hinges, and thumbscrews instead of latches to hold the doors closed. AluSig was made of traditional aluminum, and DuraSig introduced a new material- polycarbonate. Minneapolis and St. Paul were quick to adopt polycarbonate, the other agencies and Mn/DOT were very slow to and only recently have switched. The early DuraSigs had an unfortunate design in that the reflector was attached to the door, which made it difficult to change the reflector or lens, as well as visors attached with fragile tabs instead of screw. They were later revised to a more conventional design. DuraSigs worked well up here where they were immune from salt spray, but tended to bake and become brittle in warmer climates.

Both 8” and 12” DuraSigs were wildly popular in the cities, and the 12” versions are still being installed. AluSigs were more popular with Mn/DOT and the suburbs, even then they were mainly using 12”, so 8” AluSigs are uncommon, and when found are normally a pedestrian signal or the yellow and green of a larger assembly.

"Alusig" 8" and 12" combo. The 9" worded, incandescent pedestrian signals are virtually extinct. 65th St. and Lyndale Ave, Richfield

“AluSig” 8″ and 12″ combo. The 9″ worded, incandescent pedestrian signals are virtually extinct. 65th St. and Lyndale Ave, Richfield

AluSig backs

AluSig backs

8" and 12" DuraSig backs. The front looks almost exactly like the AluSigs except being polycarbonate. W Calhoun Pkwy and Lake St.

8″ and 12″ DuraSig backs. The front looks almost exactly like the AluSigs except being polycarbonate. W Calhoun Pkwy and Lake St, Minneapolis

Durasig front view and internals. It was later changed to a more standard design. The green section shows what a back of an LED module looks like, these mount to the doors in place of lenses.

DuraSig front view and internals. It was later changed to a more standard design. The green section shows what a back of an LED module looks like, these mount to the doors in place of lenses. From my personal collection.

This concludes part 1. Part 2 continues with later Eagle models and other companies.

About Monte Castleman

Monte is a long time "roadgeek" who lives in Bloomington. He's interested in all aspects of roads and design, but particularly traffic signals, major bridges, and lighting. He works as an insurance adjuster, and likes to collect maps and traffic signals, travel, recreational bicycling, and visiting amusement parks.

23 thoughts on “A Spotter’s Guide to Traffic Signals, Part 1

    1. Monte Castleman Post author

      Yes. Part II will be newer Eagle stuff, Econolite, McCain and the three programmable visibility models. I just need to get a couple more pictures, I’ll get one of the 3M internals to show how it works.

  1. T

    As some one who works in the field retiming signals, I love this post. Its good for people to know just how much goes into something that everyone kinda takes for granted. There’s a lot of planning (and unfortunately limitations) involved than you might expect. On an unrelated note, how do you obtain your signal heads in your collection? Do you go to city auctions or something or do you just have a buddy who gives you a call when they get replaced?

    1. Monte Castleman Post author

      There’s a couple of sources:
      1) Direct from cities and contractors, or via city auctions. A lot of the old Minneapolis Eagle signal heads are hitting the recycle bin with the city re-timing project. I suggested to the engineer in charge of that that they could get several times scrap value by auctioning them off, or selling them to me direct, but he wasn’t interested (I suppose I could try Public Works directly). I’ve seen old Eagleluxes in the city scrap metal bin. On the other hand I noticed a replacement project in the suburbs. I emailed the contractor asking to buy the 3M and a few of the pedestrian signals. He instead told me to make an offer for everything, so I paid half again as much for 22 signals, mostly 12″ AluSigs. He got some cash, somewhat more than scrap value, and got rid of them without having to have an employee strip down and haul them. Some of them I kept, the broken and badly corroded ones I stripped down and scrapped, and some I’m selling to other collectors, or eventually to anyone on Craigslist and eBay. In turn I’ve bought some from when other collectors got a haul- I’ve worked with people from New York and California to get equipment representative of those areas.

      2) There’s always eBay, but caveat emptor. A lot of the stuff is wildly overpriced, and there is often a bidding war when something desirable comes up.

      3) For a while (it’s been a while since I’ve seen anything) Ax-Man would resell equipment from St. Paul. The flatback and DuraSig in my pictures both came from there.

      4) Some collectors have worked directly with distributors to buy new, but there’s a general disinterest among distributors because collectors only want one, and then often back out when they find out how much it would cost.

      Generally speaking 8″ is more desirable than 12″, aluminum more than poly, incandescent more than LED, older more than newer. Neon is sought after, as are some of the rarer lenses. A 12″ LED poly is basically worthless. An Acme (the Stop/Go flags from old Hollywood movies goes for over $10,000. A typical “man cave” light- a 60s-80s 8″ aluminum of no particular rarity like a flatback is normally $100-$150

  2. Catherine

    Cool post! I love learning about things that most of us just take for granted. I wonder, are the horizontal traffic signals they have in other states (like Wisconsin) made by the same company, or by a different one that only makes horizontal ones, or what?

    Are there benefits/drawbacks to installing them horizontally vs. vertically?

    1. T

      I’ve heard that in Minnesota, they like to install them vertically so that colorblind drivers know that red will always be on top and green will always be on the bottom. Don’t know how much validity there is in that statement though.

      And I think horizontal heads are good if conditions ever get really windy, just because there’s less torque on the mast arm.

      1. Matt SteeleMatt Steele

        MN has some doghouses, correct? Does WI ever use the doghouse design, or are they always horizontal?

        Wisconsin is rather unique with their intersection design. Their standard seems to be to have medians separate the left turn lanes from the through lanes, and they have a stoplight at the stop bar rather than one on the right side mast opposite the intersection. I’ve heard Sconnies say they ran stoplights the first few times they were driving in MN because there wasn’t a stoplight at the stop bar.

        1. T

          Yup, Minnesota has dog houses, but I’m not sure on the Sconnies’ opinions on them. I’ve heard that if a signal is getting re-done, they’ll make it vertical, whether its a doghouse or fully vertical. I think they’re trying to get a big push for flashing yellow arrow, just like MnDOT is.

          And I’ve never noticed that about Wisconsin, even though I grew up right across the river from Lacrosse. Kinda weird driving in a different state or bigger city sometimes. It’s like the rules of the road are the same, but stuff might just be a little bit off.

        2. Monte Castleman Post author

          There’s been doghouses used on temporary span wire signals for a long time (where it’s difficult to support a five-light vertical), but the new Mn/DOT standard is a doghouse with a flashing yellow arrow for option lanes, so they are starting to appear permanently. I don’t think Wisconsin ever used or is now using doghouses.

          Here’s a video I took of one last fall.

    2. Monte Castleman Post author

      They’re all the same companies. Sometimes the door is slightly different, but most times the visors are just rotated 90 degrees- for modern signals visors are a separate component and are attached by four screws.

      As the next poster mentioned, horizontal mounting has less torque in the wind, so you can use flimsier mast arms (like Wisconsin) or they’re less likely to be damaged in a hurricane (like Florida). Occasionally there is also a clearance issue.

      BTW, Wisconsin’s new standard uses vertical mounts, but obviously there’s lots of older horizontal ones left, and will be for some time.

  3. Reuben CollinsReuben Collins

    I absolutely love this post. It’s Wonktastic in all the right ways. Also, very happy to see Monte authoring posts here at streets.mn. I am greatly looking forward to Part II of this series.

    Monte, you’ve focust on Eagle hardware in this post I presume because of it’s popularity in Minnesota. What were some of the other manufacturers that were making signals back in the 30’s-50’s? What do the model names mean (on the KB63, what is KB? what is 63?)?

    After you finish Part II of signal heads, you can move on to the history of cabinets & controllers!

    1. Monte Castleman Post author

      Model names are confusing even to enthusiasts which is why they tend to use slang rather than model numbers. KB63 was their standard single faced three light head with no additional heads and with no additional hardware, there would be dozens of variations of the model number if you wanted them (the 3 at least stands for “3 sections”). Eagle has been bought and sold so many times and it’s been so long I doubt even they’d know either why they picked “KB” as opposed to “XY” or something else.

      There were literally dozens of manufactures- GE, Crouse-Hinds, Econolite, Darley, Southern Autoflow, Marbelite. Even the city of Milwaukee manufactured their own signals for a time. This article was approaching 3000 words, so I condensed it to 2000 words in two parts while still covering more than 99% of the hardware in Minnesota, it seemed logical to break it up into “Eagle” and “Other”, though to split it evenly I had to save later Eagle products for the second part.

      1. Monte Castleman Post author

        Oh- as far as an article on controllers. It’s something I’ve thought of, but I don’t own a complete cabinet (it’s on my wish list to get both a modern cabinet and an electromechanical controller), and don’t have a lot of my own pictures- the outside of a city cabinet isn’t particularly interesting. I do have a real controller and load switches, but it’s just sitting on a shelf. (and PEEK was nice enough to send me new firmware chips for it for free).

    2. Betsey BuckheitBetsey Buckheit

      Rueben, I see this post as a kind of followup to your streetlight post. I enjoyed both since they help those of us who are just casual observers of lights learn a lot; experts can discuss the details. Looking forward to more from both or either of you!

  4. Sean Hayford OlearySean Hayford Oleary

    Perhaps you’ll cover more of the broader signal design issues in Part II, but I am curious about the changing ways that lights are positioned. In Minneapolis, the vast majority of the old signals were simple posts, whereas all new ones seem to either use a mast arm right away (when facing a major street), or at least on posts where a mast arm could easily be installed (when facing a minor street). Outside Minneapolis and St. Paul, I rarely see just the post-mounted, although I can think of one each in Bloomington and Richfield.

    Has there been study or change of opinion on the effectiveness of the post-mounted lights? There’s also another design, of two mast arms extending diagonally into the intersection, rather than directly perpendicular to the street. I’ve seen that at 64th and Penn.

    Another design feature that I don’t see much on newer streets is placing the signal post and arm in the median of a very wide street. New Brighton Blvd and Olson Hwy in Minneapolis are configured like this.

    1. Monte Castleman Post author

      There’s enough variety of signal equipment out there that in this series I don’t have a lot of space to get into traffic signal history or design philosophy, but as far as overhead masts, I don’t know of any studies saying they’re “X” percent more visible (or for that matter 12″ vs 8″ heads. 12″ heads are from the 1950s when you started to have high speed, high volume roads in the suburbs combined with a push by the signal companies to sell bigger and more expensive heads and to differentiate their product. 8″ heads are still allowed on lower speed roads, but both Minneapolis and St. Paul choose not to use that option.) Someone likely made an arbitrary decision that the extra visibility of masts was worth the cost (and now that you’re dealing with polycarbonate heads and LEDs the smaller extra cost of 12″ probably doesn’t make it worth stocking multiple parts even if they’re not needed for visibility on slower speed, lower volume streets.

      Minneapolis and St. Paul do things there own way, but the “small pole in the median” is being eliminated by Mn/DOT and the agencies that follow them because drunk drivers or cell phone gabbers knocked them over too often (It’s common to see a new galvanized center pole with black plastic heads while the rest of the intersections is the older style painted poles with yellow heads. Eliminating center poles and ever increasing width of suburban intersections has caused Mn/DOT problem in getting longer mast designs and beefier foundations to go with them. With larger posts in the median they’re still hit often and cause substantial damage to the car and possibly the occupants, so with the longer masts being approved now you’ll probably not see too much of this.

      The “two diagonal masts” seems to be limited to older Hennepin county installations, and they haven’t done it since at least the early 1980s.

  5. Sean Hayford OlearySean Hayford Oleary

    One other detail question I’m curious about. In Scandinavia (especially Copenhagen metro area) most new LED signals do not have visors. See this example. It’s a quite elegant look, but I’ve never seen it in Minnesota or elsewhere in the States. Is the light from these just less bright? Or do they just assume the sun has less glare in Scandinavia?

    1. Monte Castleman Post author

      I have no real answer apart from the obvious “that’s the way they do it” One thing I do notice is those signals are “exposed LED look” which are less prone to sun phantoming (when a signal looks like it’s on when it’s not due to the sun shining in) than older incandescent or new “incandescent look” LEDs.

  6. Monte Castleman Post author

    I appreciate the compliments, everyone. Thought I’d start with a post about something less controversial than how much I like the suburbs, freeways, and road trips… And I’m not sure how good of post I can do about that anyway, beyond saying I like freeways and driving, which everyone should know by now. I thought about doing “a view from the suburbs” type things, but I hesitant to speak for other people. And I’m not sure how geeky I can get, on a traffic signal collectors board I’ll go as far as to take picture of the insides of various types of LED modules, and there’s discussion about things like the different kinds of ID tags used in the Eagleluxes. From the responses I think I struck a good balance of what to include here.

    Beyond part 2, Some ideas I’ve had:
    *The history of pedestrian signals, which I can share some more interesting stuff than just what’s found here (this area is incredibly boring compared to some of the older ones on the coasts (like the neon lettered ones I’ll sneak a picture into in Part 2).

    *To keep the articles manageable I couldn’t go much beyond “this is what a flatback looks like, they were made from XX to XX”, so I could go more into the history and philosophy (although I know more about the former) that one commentator suggested.

    *Some people are interested in controllers. I certainly know a few things having wired up and programmed one (Basic 4 phases plus 2 peds, everything on recall, tried to set up preemption but haven’t gotten it to work right yet). But I don’t own a complete cabinet nor an E/M controller (though both those are on my wish list), so I wouldn’t have that much for pictures and don’t know how geeky I can get.

    I could show how to program it for a basic intersection, again I don’t know if that would be too geeky of if some people might find it interesting. As I’ve hinted in comments, older firmware can’t always do things that people here want. It’s more complex than an engineer just going out and throwing a switch to turn on a leading pedestrian interval.

    *Suggestions for revising the signals and streets in my neighborhood to make things easier for pedestrians without really affecting cars all that much

    *Something to do with my map collection.

    *The history of Minnesota highway markers and the trunk highway system.

    1. Reuben CollinsReuben Collins

      No matter what you write, it will be too geeky for some, not geeky enough for others, so don’t sweat it. I agree you’ve nailed the balance in this post. I loved this piece, and am greatly looking forward to reading your future posts.

  7. Pingback: A Spotter’s Guide to Traffic Signals: Part 2 | streets.mn

Comments are closed.