Common Questions About Traffic Signals

September 15, 2016 at 12:36 am | Posted in Traffic Signals | Leave a comment
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Here are some random questions and answers about traffic signals that didn’t deserve their own article.

1) What can pedestrian sensors do?

Although pedestrian sensors are uncommon for all the usual reasons (cost, engineers don’t see need, old equipment, etc), there are some neat things they can do. Besides being able to call a pedestrian phase if a pedestrian is present, a second sensor can be mounted pointed toward the crosswalk. This can extend the pedestrian phase if the pedestrian is especially slow. Or conversely terminate it early if it’s a runner or bicyclist. Perhaps by mounting one farther back on a multi-use path they could call a phase if a bicycle or pedestrian is approaching, hopefully giving a walk signal by the time they reach the intersection. The idea is not new; some early ones experimented with pressure sensitive plates, but modern ones use microwave detection.

2) Why do we still have push-buttons if the “Walk” sign always goes on (ped recall)?

This is covered pretty thoroughly in previous articles and my comments to them, but basically ADA (at least as implemented in Minnesota) absolutely requires a station with  audible and tactile feedback (in the form of an arrow that vibrates) next to the crosswalk.


Shiny new audible-tactile push-button on and old signal

First, a station that includes feedback, with all the sophisticated electronics and simply lacking one mechanical button doesn’t make sense, either to produce as a product or for agencies to stock spares for. You’re probably talking about a part that wholesales for a couple of cents for a $400 station that’s part of a $6000 system (and can cost well into five figures to retrofit an existing intersection).

Second, if there was a station without a button, it would still look like it had a button, people would push at it and be confused when it doesn’t move or do anything (if ped recall is enabled or the button has already been pushed the speaker says “Wait”, but it doesn’t affect the cycle.) There’s already a myth that pedestrian buttons don’t “do anything” (that apparently started in New York when they converted from actuated controllers to fixed time and disconnected the buttons without removing them).

The Econolite push-buttons, as used with the famous California neons, would turn a small red light to green to acknowledge that the button had been pushed. This was probably not more widespread due to the maintenance of the incandescent lamps, and has now finally been coming back with the new electronic buttons.


Agencies vary widely in how rapidly they are bringing existing infrastructure into compliance with the ADA. Not just traffic signals, but removing utility poles from the middle of sidewalks.

Guidance in the past has been vague, for example the MUTCD does not require accessible signals, and disability rights groups have in the past conflicted with each other, but finally the FHWA made the statement:

“Implementing regulations for Title II of the ADA, which covers State and local governments, also address “communications and information access,” requiring ‘effective communications’ with persons with disabilities. In the sidewalk/street crossing environment, this would include accessible pedestrian signals, markings and signage.” (FHWA, 2004).

And with the “Public Right-of-Way Accessibility Guidelines” (PROWAG) under development, it is expected accessible pedestrian signals will be mandatory.

But the ADA only requires modifications to existing infrastructure when it can be done without “undue financial or administrative burden.” So far, modifications have been up to the whims of individual agencies and how far disability rights groups want to push things. Minneapolis and Hennepin County, for example, aren’t always using them in new construction. By contrast, MnDOT, which was pushed by disability rights groups, feels they have to include them every time they go smooth out some bumps in the road, and will actually remove crosswalks rather than leave them noncompliant or upgrade them.

3) Why aren’t there more leading pedestrian intervals?

There generally is an impact to motorists, as you more or less double the time they cannot use the intersection (the exception being if the pedestrian phase is long enough and motorists few enough that motorists don’t fully utilize the green time if a pedestrian phase is present), but they are such an advantage to pedestrians that they are beginning to be implemented in areas with heavy pedestrian traffic anyway (one study showed a 60% decrease in vehicle + pedestrian accidents).  The MUTCD only specifically allowed them in 2009, so there are the usual issues with older equipment not having the capability, and of resources required to implement them.

One area where I feel a leading pedestrian interval would be appropriate is Berry/Calhoun Parkway and Richfield Road. This has a lead left and in practice pedestrians and bicyclists on the very heavily used trail often jaywalk as soon as the cross street turns red, or at least get confused when they don’t get an immediate walk (It doesn’t help matters that during non-peak period it is permissive only). It would be better as a lag left with recall enabled and a leading pedestrian interval.


Calhoun Parkway and Berry Road

4) Why won’t the light turn to “Walk” if the same direction has a green left turn arrow?

Sometimes it’s just the engineers didn’t think of it and implement it, but this requires the “pedestrian overlap” outputs on the controller be used, not the standard outputs, with associated reprogramming as well as additional load switches. The controller may be old and simply not have that capability. There may be no room in the cabinet for more load switches. Implementing this certainly requires wiring changes in the cabinets. Always much more complicated than setting a menu item on a controller


Simple Traffic Controller Cabinet

Here’s a typical cabinet, you can see in #4 that load switches plug directly into the backplane, #3 If there are no empty sockets you basically  have to replace the cabinet, probably with a bigger one, and thus probably requiring concrete work… You can’t simply shove an extra load switch in some nook and cranny.

5) Why, when I pull into the turn lane, does the side street turn green first with no one there?

First, it could simply be a fixed timed light where there is no sensing of vehicles. Second, skipping phases where there is no demand is a fairly recent concept. It simply didn’t exist in electro-mechanical or early electronic controllers. So it might be that no one has worked on and upgraded the intersection recently.

Or, the loop detector could be broken, as often happens. If they break they are supposed to default to the “sense” position so calls are always generated.

6) If the cars have the green light why don’t I get a “Walk” signal when I push a button?

“Pedestrian Reservice” does exist and is an option on most modern controllers, but is subject to the minimum pedestrian phase time. You can’t promise the controller “If you give me a Walk, I’ll hurry across.” Since walk intervals tend to be short compared to clearance time, there’s usually not time to give a walk if a pedestrian is not there before or at the beginning of the vehicle phase.  Simply extending the vehicle phase until the pedestrian phase can get done would lead to all kinds of issues with coordination. The “Home Depot” intersection previously discussed does have reservice even if it doesn’t have recall to cross the driveway and side street.

To me this is somewhat redundant, since if a phase is long enough to allow ped reservice, it’s long enough to allow ped recall, but the concept does exist.

7) Why don’t signals flash at night or during times of low traffic?

Nothing’s more irritating than coming across a red light late at night when no car is in site. In Minneapolis where there are many fixed time intersections, it can even be a while before it changes. Basically night flash was removed in Minnesota because there have been a number of studies that it’s safer to have full operations 24/7, as well as actuated lights becoming increasingly common. Various studies show a reduction in night-time accidents from 27% to 95% when signals run 24/7. In theory if a light is red, it should turn green as soon as a motorist arrives at 3:00 AM.

As I’ve mentioned repeatedly, engineering fundamentally balances efficiency and safety; Minnesota engineers try to tilt the balance towards safety as opposed to efficiency in a lot of ways, most visibly with how prevalent protected-only turns are (Only in California have I seen more); this balance explains why night flash is extinct in Minnesota. With the increasing number of actuated lights and the introduction of right turn on red, motorists at least don’t have to wait as long as they would have in days past.

8) Can I change a traffic light to green with my TV remote or flashing my headlights?


Longer answer:-That Youtube video is a myth/prank/joke.


Preemption is triggered by a strobe light mounted on emergency vehicles that flashes at a rate different than what a commercial strobe light will do. After electronic geniuses started building their own triggers, Minnesota specifically outlawed having one in your vehicle (although I have one for my home setup). And in case anyone still has ideas, they’re not easy to build; they require more precision than can be obtained with simple “Electronics 101” type resistor/capacitor timer circuits.  Also, they won’t work on the street anyway anymore, because the flashing is now encrypted.

9) What are those blue lights on some traffic signals?

To tell the cops waiting in the next driveway you just ran a red light. The first installation was at the now replaced signal at County 5 and MN 13 in Burnsville and was improvised with a standard industrial fixture; now there are specialized LED lights available. Also, those cameras on top of the signal mast are not “red light cameras,” they’re generally video cameras or microwave sensors for detecting cars, and go no farther than the traffic cabinet. Some MnDOT intersections do have traffic cameras, but they are mounted much higher up.



10) What about driver-less cars?

I really am excited about driver-less cars.  Imagine being able to start out to Chicago at night, fall asleep, and then arrive in the city with my car in the morning. Imagine editing a post for while stuck in traffic. Imagine ordering fast food, or even slow food, on a touch screen and it would be ready when you pull up (and a lot easier and safer to eat in your car). I’d probably eat at Applebee’s instead of Arby’s if it were just as convenient.

But getting back to the topic, think of how fundamentally unchanged the interface between traffic signals and motorists is despite nearly 100 years. A traffic signal controller can only tell if a car is there or not, not how many are there, or how many will be coming it’s way in five minutes. A driver can only see and react to a red light, not know there’s a string of red lights five miles away. So it’s easy to see how revolutionary cars communicating with traffic control equipment could be: No wasted reaction time, signals which know all about traffic and can react accordingly; cars which can reroute if there are a bunch of red lights ahead. Despite frustration with the present, I see great optimism for the future.

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How Traffic Signal Controllers Work, Part 2: Programming a Modern Controller and a Look at Their Limitations

September 11, 2016 at 1:34 pm | Posted in Traffic Signals | Leave a comment
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This is Part Two in a series about Traffic Signal Controllers. Part One showed various types of controllers and cabinets, here we continue with a closer look at a 1980s-2000s vintage controller: the Eagle EPAC 300, a 16 phase NEMA (National Electrical Manufacturers Association) TS-1 controller.

Eagle EPAC Controller

Eagle EPAC Traffic Signal Controller

There’s not much to it on the outside: a membrane keypad and LCD screen for the interface and the “ABC” cables at the bottom for the inputs and outputs. The “A” cable feeds AC power to the controller, DC 24 volts from the controller to run the load switches, and all the inputs and outputs for a simple 2 phase intersection. The “B” cable adds phases three and four, and the “C” cable add phase five through eight. Each wire has a single fuction; there is no serial communication with the cabinet.

To the lower right of the controller are serial connectors for communications equipment, generally to a master controller or a traffic control center.  Most newer controllers it’s possible to hook up to a computer with serial connections, and even newer ones may have integrated USB and Ethernet ports, but this is generally only done for initial programming. EPAC stands for Eight Phase Actuated Controller, despite some early units available with only two or four phases, and newer units having 16.

NEMA, conceived in simpler times, only had physical inputs and outputs (I/O) for eight phases. To use more than these, it’s necessary to electronically remap some of the I/O used for other marginal to useless features. NEMA has many features that either were never or are no longer useful; the I/O can be remapped and reused for other things on newer controllers, for instance there is a provision to have a “yellow” light for pedestrian clearance phases. Since instead the “Don’t Walk” is flashed, and these are in the cabinet wired to a the spare center section of the pedestrian load switches, these are normally used to drive things like pre-emption lights and blankout signs. Some controllers also had a proprietary “D” connector for such things.

NEMA controllers can operate by themselves as free-running controllers, or as a master controller that coordinates many of them. The EPAC 300 series is more or less still in production as the M50 and M60, though the Eagle name has been removed and is still owned by Siemens after the Eagle signal head business was sold off to Brown Traffic.


Some of the Screens

Although there are many screens, these can be broken down into (1) “Status” screens, that show what the controller is doing or logs of what it’s done, and (2) “Programming” screens where you enter what you want it to do. I’m omitting anything having to do with: Density and Time of Day Programming (where cycles change based on traffic volume and time), Coordination, Logging, Communication, Start up Sequence, Preemption, and Flash Mode. These are probably of marginal interest to non-engineers, some of these I don’t understand myself, and skipping them eliminates probably 95% of the complexity. Also omitted is anything having to do with actuation. Although some collectors will add video detection and pedestrian push-buttons to their setup (and there’s an amazing variety of buttons to collect), I have chosen not to. I have four phases with two associated pedestrian phases that run in sequence without waiting for calls.

Here is the main screen:


Let’s see what it’s doing first: go to 1-ACTIVE STATUS and then 7-INTERSECTION. The second line shows the phases and then “V-SIG” says they’re all red except phase 4 is green, below that P-SIG pedestrian outputs are “D” for “Don’t Walk” except Phase 4, which “d” means it’s flashing the “Don’t Walk” for the clearance interval. All the phases with physical outputs (1-8) default to red and “Don’t Walk” all the time unless programmed otherwise. In this case 4-8 are not programmed. If there were any Calls,  these would be indicated under V-CALL and/or  P-CALL. The Overlaps, with letters instead of numbers are additional outputs for driving such things as a protected/permissive display where you have a green ball and green arrow in the same direction. Not all of the vehicle overlaps have designated physical outputs. There are also pedestrian overlaps on a different screen (where you might give a “Walk” signal on one side only if there’s a green arrow the same direction; none of these have physical outputs).



Now suppose we want to play with things and see where values can be entered and changed. Go back to the main screen, select 3-PHASE DATA, then 1-VEHICLE TIMES. The MIN GRN  is the green  time in seconds for each vehicle phase. Phases 5-8 (and 9-16 on the second screen if you page down) have default values except for the zeros for MIN GRN, which disable them. PASS/10, MAX # 1, and MAX # 2 would extend the green if needed vehicle detection was used, since they’re not here they have no effect and  the controllers default values are left in place here. YEL/10 and RED/10 are the yellow and red times in tenths of seconds.



Going back a screen and then to 3-PEDEST. TIMES. Phases 2 and 4 have pedestrian signals hooked up, with WALK time at 30 seconds and PED CLR. at 20 (5-8 will not activate since there are no associated vehicle phases and the numbers you see are default values). The FL WK will flash the walk light, now a MUTCD no-no, but previously used in DC to indicate a crosswalk where there vehicles might attempt to turn across. EXT PCL will continue flashing the “Don’t Walk” through the red and yellow vehicle phases. ACT RIW will hold the phase at “Walk” until a conflicting call come in.


Going back a screen and selecting 5- V&P RECALLS, we see Recall is selected for all four vehicle phases and both associated pedestrian phases (indicated by a “2”) So it will go through the cycle and service all phases without any demand from pedestrian push-buttons or pedestrian sensors. Entering a “1” will generate a call to test the controller in case physical test buttons aren’t provided in the cabinet. DELAY allows you to set a time before Recall is activated.


Why Can’t Signals Do What We Want?

Quite often the question gets asked  “why can’t a traffic signal do this, or why doesn’t it do that”.  Now with a bit of understanding of controllers and  cabinets,  lets go over a couple of  broad reasons why things are or are not done a certain way.

mnmutcd-cover1) It’s required or banned. The Minnesota Manual on Uniform Traffic Control Devices (MUTCD) based on the federal one with some very minor changes, has options , strong suggestions, and absolute requirements. Engineers are not likely to deviate from suggestions, and may not deviate from requirements. Banning creativity might preclude the best response to a specific situation, but on the flip side road users can expect uniformity nationwide. When traveling, they’re not going to encounter a flashing purple arrow in Peoria or  a pink strobe-light in Paducah and then have to try to figure out what those mean. If a city really wants to try something new out, say a red arrow on top of a standard three light signal to emphasize no turns on red (not currently a legal configuration), they can apply for permission to experiment, do a study, and then either remove it if a study shows no benefit, or it may be adopted into the MUTCD if it does.

2) It’s often a zero or negative sum game with intersection capacity a fixed resource,  since  pedestrians and motorists compete for the same resource, and the needs are completely opposite. Right on red or longer overall cycle times: pro-motorist, anti-pedestrian. Exclusive walk phase or leading pedestrian intervals: anti-motorist, pro pedestrian. Other people may not see it this way, and are surprised when I describe “pedestrian improvements” as “anti-motorist”, but ultimately that’s the effect even though there may have been intent to harm vehicle operations (although sometimes there is). Additionally since pedestrians move a lot slower, sometimes a very modest benefit for pedestrians can produce an extremely severe impact for motorists, like ped recall across a wide suburban-style road. More details on some of these scenarios will be in the next part.

3) A lot of equipment on the field is very old. Even computerized controllers tend to use  1980s vintage microprocessors like the Motorola 86040, and the need for standardization  dampens innovation. This is more true in the cities were demand for pedestrian amenities is greater. Until very recently Minneapolis even had electro-mechanical controllers.  Old controllers may not have the capabilities that people want. But it still works and cities are not made of money. In some cases even what seems like a minor change could require a complete cabinet replacement, or even a bigger cabinet requiring a bigger concrete pad and redoing a lot of the wiring, and the cities are not likely to do that just because someone wants a leading pedestrian interval or something.

Eagle Electromechanical Traffic Signal Controller Cabinet

Eagle Electromechanical Traffic Signal Controller Cabinet

Although we’ve come a long ways from a free-running E/M controller in every light, even the newest controllers are nowhere near as powerful as a PC. (You may have noticed the line “16 MHz CPU” and a 2000 firmware date on the main screen of mine.) Even if they were, in most situations the input and output are still limited, with the only input available being  vehicle sensors and pedestrian buttons and only output being lights. They can’t look at a a bunch of cameras focused on the intersection and down the block and make decisions based on it, or sound a fog horn if they see a motorist inching into the crosswalk.  Things are getting better with multiple vehicle sensors that can thus measure vehicle speed (one controller even has a “feature” that will turn the light red if an approaching motorist is speeding) and the new Linux based controllers that are more flexible in certain ways.

Sometime upgrading the firmware on existing equipment is possible, but besides the expense and need to go out and swap out chips or update the flash memory, engineers like to have known, stable, and consistent firmware. At least once Mn/DOT has had to back out and revert to an earlier firmware version because of bugs. Mine is running 2000 firmware and would require an upgrade to do leading pedestrian intervals.

There is also the “SMART” Signal system, which tries to harvest and aggregate data gathered by standard controllers together using industrial PCs and use it to dynamically optimize timing in a way that’s not possible with traditional manual coordination. The controller is an Econolite ASC series, the Mn/DOT standard and most widely used in Minnesota.


4) Old-Fashioned engineers. To end with the elephant in the room, sometimes it really is engineers that are just set in their ways and not taking the needs of pedestrians seriously or being open to modern ways of doing things. And it’s not just signals; they admitted the trails associated with the St. Croix Crossing are only worked on “as we have time”.  And closed down the sidewalk on the Hastings Bridge for the entire duration of the project even when there was no work being done anywhere close to it. However the point I’m trying to make is there usually more too it than some “dumb engineer sitting in a chair in Medina” not wanting to put down his donut in order to click an icon on the computer in front of him.

Overall, the idea isn’t to pass value judgments or state my opinions on what is or is not a worthwhile change, even though perhaps the fact that 95% of the time I’m  a motorist shows through. Rather, what I’m trying to do is lay out the reason things are the way they are.

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How Traffic Signal Controllers Work, Part 1: An Overview of Controllers

September 10, 2016 at 2:37 pm | Posted in Traffic Signals | Leave a comment
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Electro-mechanical Controllers.

Crouse-HInds PCE-3000 E/M traffic signal controller.

Crouse-HInds PCE-3000 E/M controller.

Electro-mechanical controllers date from the beginning of traffic signals up to new installations in New York City into the 2000s. I’ve placed a few short videos below, and there really is no substitution for viewing them to get a sense of how them parts move, but here’s a description and some still pictures first.

1) A dial with keys on it rotates, very much like a mechanical timer. Some used multiple dials for different timings on different times of day. The speed of the rotation is controlled by different gears that can be installed.

Crouse-Hinds Electromechanical Traffic signal controller dial

Dial and Keys

2) As the keys pass a micro-switch they temporarily close it to activates a solenoid or motor. The motor rotates a camshaft with cams. Each cam has lobes that can be moved or broken off around the perimeter. The knobs hold an array of piano switches open. Removing a lobe causes an individual switch to close when the cam is in that position. Each signal indication on each street is wired to one of these switches.

This is the simplest possible installation, a two phase, no red clearance operation. The first key changes Main Street green to Main Street yellow, the second changes Main Street yellow to red and Side Street red to green, and so on. The key in the middle prevents the cams from getting out of sync by not allowing it to advance unless it hits a switch.

Crouse-Hinds Electromechanical Traffic Signal Cotnroller Cams

Camshaft, Cams, and Switches. Note some switches are in the closed position due to the metal lobes being removed from the cam, and some of the cams are color coded. Here the Main Street Green and Side Street red switches are closed and thus the lights would be lit.

Coordination is actually possible with E/M controllers. A mains wire runs from one controller to another, and a relay removes AC power to the controller downstream to prevent it from getting out of synch.

Video 1: Shows the outside of the controller

Video 2: Shows the inside and the dial rotating:

Video 3: Shows the dial, then the cams

Video 4: Closeup of the cams

This area tended to use Eagle E/M controllers. Crouse-Hinds controllers like mine (from probably the early 1970s in Moberly, MO), used motors instead of solenoids creating a whir instead of a clunk when moving the cams. Also, the cams have metal lobes that are replaceable, so if you make a mistake arranging cams or want to change things you can. With Eagle and other brands if you break a lobe off that’s it, you need to replace the entire cam to undo it. Cams are still available from one supplier, but there’s talk from signal collectors at having them 3D printed due to the expense and hassle of working with distributors.

In some ways E/M controllers can be even more flexible than early electronic ones. There’s no reason you couldn’t “program” leading pedestrian intervals or even flashing yellow arrows, something early electronic controllers are not capable of.

Hybrid Controllers

E/M Controllers may work well for fixed time applications, but they did not really handle actuation (where they respond to serve a vehicle or pedestrian phase).  This was more important with the rise of the suburbs, where traffic demand is less predictable and fewer traffic signals exist, rendering fixed time inefficient. Basically the timing was generated by vacuum tube electronics charging an absolutely huge oil filled capacitor, which would eventually discharge through the solenoid, moving the cams. The rate of charging, and thus timing was controlled by knobs on the front which are variable resistors.

Other items in an E/M or hybrid cabinet might include E/M timers to switch dials or put the cabinet in night flash, an E/M or electronic flasher, and transfer relays.

Electronic Controllers.

The first electronic controllers were designed as drop-in replacements for E/M controllers and used a lot of the same terminology and philosophy. The times were set by knobs and dip switches and such and each brand was proprietary. Gradually a standard (NEMA TS-1) was implemented to the connector from brand A was the same and each wire would do the same as brand B, and certain functionality was required, so you wouldn’t have to essentially replace the cabinet to switch controller brands. Later controllers went to a keypad with a few numeric LEDs, to program them you’d look up on the manual something like “Function 132 Main Street green time”. Later LCD displays were much more user friendly. Philisophically there was a switch from “percentage of dial times’ to programming in phases.


There are a few traffic signal collectors that tinker with these early controllers. Very few. Some of the flashing LED displays are fun to watch, but the connectors and documentation are hard to find, electronics do not age well, especially when unplugged for extended periods of time, and newer, much more user friendly, reliable and versatile models are available at attractive prices. So collectors usually use newer electronic models, or else old cool E/M ones.

Electronic Controller Cabinets 

Here is a simple demonstration cabinet with the components annotated.


Simple Traffic Controller Cabinet

1) The controller itself: The actual controller. Inputs and outputs are 24 volts DC,

2) The conflict monitor: makes sure that the controller doesn’t mess up and do something like turn both directions green. If it detects something like this of if the controller fails, it will put the signals into flash

3) The back panel- contains the terminal blocks (towards the left), flash transfer relays (towards the right), and sockets for the load switches and flasher (towards the bottom)

4) The load switches: These take the 24 volt outputs of the controller and control the mains electricity to the signals themselves, essentially solid state relays. Each load switch can control up to three indications, generally the red, green, and yellow of a single direction.

NEMA Traffic Light Flasher Module

NEMA Flasher Module. the load switch is similar but has a third solid state switch module instead of components on the main board.

5) The flasher: Generates a flashing signal independent of the controller, so the signals can still flash if the controller itself goes down.

6) Circuit breakers and power filters

7) Manual control and test switches

In the real world it would likely be jammed full of equipment. The second shelf would have fiber optic communications equipment and pre-emption equipment, the manual controls would be mounted to the door and the top shelf filled with loop amplifiers or video detection equipment.

A newer standard is TS-2, which replaces some of the hard wiring with serial connections. Also available are 2070 cabinets, where the hardware is purchased separately from the software, and the controller is more modular, accepting various function cards. Minneapolis uses 2070 cabinets, the other agencies use NEMA.  The newest controllers are ATC, which combine some of the elements of NEMA and 2070 controllers and run on standard Linux, enabling more flexibility with software programs.

My Own Collection:

Here is my home setup. It’s a four phase sequential setup.  It lacks a conflict monitor (they are difficult to wire and in a home setup serve no real purpose unless you own a real cabinet, in which case it’s a pain to rewire the whole thing to not need one). Beyond the bare minimum to run some lights (controller, cable, load switches) it has a flasher and flash transfer relay, and some manual switches to put it into flash mode. The controller is an Eagle EPAC 300. Despite using Eagle signal heads, their controllers are not really used in this area. The EPAC series is a favorite of collectors since it’s (relatively) simple, new enough to be reliable but not too new to be complicated and expensive, and other collectors use them so help programming is available. I know there’s exposed wiring, but  it’s semi-protected and is in the basement where the pets don’t go.


Home Setup

The controller I got for $75, and the load switches I got eight for $50 on eBay. Surplus dealers will buy a bunch of stuff at municipal auctions and try to flip them, not knowing that they’re essentially worthless unless an occasional collector wants one. No city is going to buy a 20 year old controller off eBay. Unfortunately the sellers can’t test the equipment and sell it “as-is”; they can’t even plug it in to see if it powers up because there’s no standard AC power cable, and it may be password protected which would require new firmware to clear.

The cables are by far the hardest to find because they tend to stay with the cabinet and get discarded when the cabinet is recycled, new bare connectors are close to $100 from electronics suppliers. I finally got some cables from another collector who is also a real signal tech. Obviously some knowledge of electronics and ability to work with mains current safely is required. But of the 175 pins on the three connectors, I’m only using less than three dozen, and a simple setup with two phases can get by with as little as 14. (10 outputs, one for each signal light, AC power, neutral and ground inputs, and 24 volt output to the load switches.)

I’ve used a bunch of terminal blocks from a local surplus store for much of the wiring. The load switches are designed to plug into Jones sockets in cabinets, but with a little coaxing they will accept standard female spade lugs. Load switches aren’t especially expensive or hard to find, but a bunch of 24 volt relays can also be used.  Wires to the signals are 4, 5, and 7 conductor “SOOW” cable, usually used for wiring industrial equipment.

Home  Controllers

It should be mentioned that all this is way overkill if you just want a traffic light in your garage or man cave. Single board  controllers are available that will drive a single signal and are easy to use. All that is involved is wiring a mains cord to the controller board, then each of the three lights to the board.  The 150 watt rating is good enough for any signal, even a 3M. Some serious signal collectors will use these too; some of them have no interest in real controllers, and may have signals scattered through their property instead of a single “signal saloon”. The main problem with these is there’s no protection on the output circuitry like a real load switch; a bulb burning out can occasionally damage them.

Finally, a video of my setup in operation. I  have fairly broad tastes (as broad as signal collecting can be) with stuff ranging from 1940s art deco signals to modern but unusual stuff to examples of signals common to this area with an interest in both lenses and LEDs and a particular interest in pedestrian signals.

Since I know people are wondering: Most of the signals I got from eBay or other collectors. The cheapest one was $25 (the St. Paul Durasig pedestrian signal); I have over $1000 invested in obtaining and restoring the neon pedestrian signal. Some collectors have bought new from distributors, but understandably they tend not to be friendly to collectors. They’re intrigued by the interest private collectors show, but at the same time they have a job to do and are more interested in a city that might buy 500 as opposed to some guy that wants one for his basement, and then decides it’s too expensive when he finds out the cost.

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