Willis Lamm's
Traffic Signal Collection

Building Controllers for the Signals

A component of any signal collection display involves getting the signals to display sequences that would have been observed "on the street" when the signals were actually in service. The signals in this collection are operated by four types of controllers. Signals having their own internal controllers can be viewed here. Controllers constructed to operate the remaining signals are illustrated below.

Click any picture to open up a larger view in a new window.
  Cam Type Controllers

Until the 1970s a vast majority of signals were operated by means of electromechanical controllers. These ranged from simple factory cut sets of cams that were turned by small synchronous motors to more complex and precise ratchet cam controllers that, in some cases, had multiple control rings. I used modern versions of the synchronous cam controller known as the adjustable cam controllers for several of the signals in the collection in order to reproduce the signal displays unique to make and model signal being displayed.

One cam timer operating two signals
Closeup View. (Boxes uncovered for photo.)
Another style cam timer.
A 6 cam timer with double throw switches can actually control two separate 4-way signals or clusters. The first cam toggles red/green. Both N.C and N.O. outputs are branched so that one lead goes to red and the other to the corresponding green/yellow cam. The opposing green is toggled to yellow three seconds before the red/green switch reverses. The third cam toggles the other green to yellow in the same manner.

                 ------------------ Main red
         Cam 1 <                  \                      --- Cross Green
                 ----- Cross Red    ------------ Cam 2 <
                     \                                   --- Cross Yellow
                       \                                 --- Main Green  
                         ----------------------- Cam 3 <
                                                         --- Main Yellow

The 4th, 5th and 6th cams can control another 4-way signal or left turn and/or ped movements.

  Relay Logic Controllers

The main part of the collection is designed to eventually appear like a series of intersections. I designed a master controller using relay logic so that the signals would change in synchronized sequence from closest to most distant. The master controller board handles 5 "intersections." Each intersection is controlled by a series of time delay relays and each intersection synchronizes the next intersection my means of an adjustable time delay relay.

The first intersection (Marbelite) has a doghouse left turn for the cross street. (This intersection is actually behind the camera.)

The second intersection (GE) is a simple 2-phase display with a button operated ped movement.

The third intersection (Crouse-Hinds) is a 2-phase display with opposing protected left turns.

The fourth intersection (Eagle) is a simple 2-phase display with railroad preempt.

The fifth intersection (assorted polys) has an arterial left turn overlap and fixed time ped movements. (The signals for this intersection still have to be hung.)

The controller board - mostly completed.

If an intersection falls out of synch (such as a railroad preempt holding up a signal,) that particular intersection will limit cross traffic to "minimum green time" until that intersection is once again fully in synch with the previous intersection.

Here's what the progression looks like. From the angle of the photos, the coordinated signals run back and to the right of the GE 4-way in the foreground.

GE intersection turns green.
C-H intersection turns green.
"Back wall" intersection turns green.
C-H intersection permits left turn.
Eagle intersection turns green.
Cycle starts all over.

View a video of the green wave on YouTube.

A detailed illustration of real on-the-street electromechanical controllers as well as central computer signal controls in Toronto can be viewed in a production by Acme School on YouTube.

View Individual Signal Sequences

Return to Signals Page