My History With Traffic Controllers

I started in this business near the end of the electro mechanical era of traffic control, at least for where I worked. During my career, systems have advanced through transistors, integrated circuits, microprocessors and into the advanced traffic control era. Below is a list of some of the systems.


Fixed timer: This consisted of a switching cam which was advanced by one to three interval timers. When I started in this business, we had one of these in each cabinet as an emergency replacement controller.

Electro-mechanical: These come in many forms. We used various models.

Automatic Signal #1826: A three phase controller that provided gap timing in addition to basic minimum maximum, and yellow timing.

Automatic Signal #1022: A two phase controller that provided added initial and three types of gap reduction in addition to basic timing.

Automatic Signal #1033: A three phase controller that provided added initial and gap reduction in addition to basic timing.

All of these utilized a switching cam to control the outputs. The cam was advanced based on timing intervals controlled by adjusting a potentiometer (knob) that varied the rate of charge of a capacitor. When the voltage on the capacitor reached the set voltage, the capacitor would be discharged and the cam would advance.

To make up a useful system, other equipment needed to be utilized.

Automatic Signal #MM3 (Minor Movement 3): This was a split phase device that received inputs from a phase (parent) of the above controllers (1826, 1022, or 1033) and provided some additional timing for an additional phase and control of the outputs of that additional phase and the parent phase.

Automatic Signal #PT2 (Pedestrian Timer 2): This device had a timer driven adjustable cam that provided “walk” and “don’t walk” outputs.

Automatic Signal #TM27 and TM30: These devices were similar to a fixed timer but had three interval timers with offset synchronization adjustment capability. They were used to coordinate adjacent intersection controllers in a coordinated system.

Automatic Signal #TM1: This device was used to determine the traffic volume on the roadway and select a cycle length and offset command for the system. Basically, the settings were used to set the charge rate of a capacitor that was charged by each actuation if the input. There were two channels one for each direction on the main road. The charge levels at the end of a sample period determined how the outputs for cycle length and offset were set. These commands were then sent to the TM27 (or TM30) at each intersection.

Each of the above pieces of equipment needed to be completely disassembled, cleaned, inspected and reassembled, then adjusted every six months. In addition to the controllers, there were numerous relays used in the cabinet to provide various control functions and to drive the field indications. They also need to be cleaned, inspected and adjusted as well. A standard van could carry enough to replace the equipment at two locations. It took about four hours for two people to change out the equipment and check operation at the two locations. Solid state and microprocessor controllers eliminated all that work.

Transistor based.

Automatic Signal MF80 (or #T1055): This was a transistor based traffic controller. It provided up to eight phases in one box but basically worked the same as the earlier controllers, just that it was solid state and didn’t utilize relays. This controller provided added initial and gap reduction along with pedestrian and max two capabilities for each phase. For our systems, the TM1 and TM30’s were still used to coordinate the controllers. It was a modular controller allowing configurations based on the number of phases to be controlled up to eight.

Integrated circuit based.

Econolite D8000: This controller utilized the first integrated circuits (Diode Transistor Logic DTL). It was quite sophisticated. But basically mimicked the operation of the MF80 controller. It did utilize digital timing rather than the analog timing used on the MF80. The timing was set using decimal dial switches. It was a modular controller allowing configurations based on the number of phases to be controlled up to eight.

Econolite D7000: This was a local coordinator used with the D8000 system. The D7000 was much more sophisticated than the older coordination system. In addition to standard cycle and offset control, it provided two pedestrian permissive periods and split adjustment based on queue length on the side street.

Econolite D9000: This master controller used either volume or occupancy to determine a cycle and offset. Our system had one of each along with a programming matrix to determine the cycle and offset for the system based on both volume and occupancy. This was one of the most sophisticated coordination systems I’ve ever seen, and not a microprocessor in sight.

Automatic Signal Series 90: This controller was unique in that it utilized wire wrapped circuitry using TTL logic and was programmed utilizing punched paper cards for each phase. It was not microprocessor based. It basically replaced the MF80 controller in an Automatic Signal system.

Microprocessor based.

Econolite EMC8000: The first single board microprocessor based controller. This uses dip switches like the SPC8000 with the interval settings in binary as well.

Econolite EMC7000: A local controller of similar design to the EMC8000 controller with most of the functionality of the older D7000. Basically the queue functions were missing. Replaced with more control of the cycles and offsets.

Econolite EMC10000: This master controller provided most of the functionality of the dual D9000 masters with the program matrix. A rather effective master controller.

Econolite SPC8000: I believe this was our first microprocessor based controller.The timing intervals were set using binary numbers with dip switches on the front panel of the modules. It was a modular controller allowing configurations based on the number of phases to be controlled up to eight. This controller included a special coordination module specific for our use called the Platoon Progression module. It basically provided a non cycle based coordination method that effectively could do mini preemptions to the main street to allow the passage of identified platoons approaching the intersection. Some people traveling the road said it worked well. Others didn’t think so? This was also a closed loop system in that all controllers could communicate to a centrally located master near the center of the 18 intersection in the system . There was some remote monitoring capabilities.

KMC8000: A microprocessor Based controller that was keyboard or system programmed using a keyboard or through system communications. Real timeclock and coordination functions were included in the controller.

KMC10000: A master controller constructed much like the KMC8000 controller used as the master to several KMC8000’s in a coordinated system.

Multisonics 720?: This controller was microprocessor based and utilized program pins to make timing adjustments. It was a modular controller allowing configurations based on the number of phases to be controlled up to eight. We had two of these controller. They were used in stand alone locations.

Traconex 290: These were microprocessor based controllers. A unique feature was the case which was similar to an apple computers construction, not the usual sheet metal construction. There was a numeric keypad for programming in addition to downloading programming. It provided normal eight phase control with real time and system control.

Traconex 390: This master controller provided a full closed loop system, our first. The computer used as the central computer was the KayPro computer, later utilizing IBM PC’s.

Eagle Marc 300?: Another microprocessor based controller much like the Traconex. It provided some powerful coordination capabilities not present in the Traconex 390. We were able to utilize this system to allow non stop runs through our eight mile 18 intersection system. Utilizing lead/lag left turns and metered entrance to the system. Quite an effective system.

Naztec 900: This Advanced Controller provides all the standard functions of a secondary controller (controller and local coordinator). The same controller is used as the Primary or master controller as well with only a downloaded program difference. At the master location, there was only one box doing all functions local controller and coordinator and master controller. This controller provided many advanced coordination capabilities. In addition, there was a burnout lamp detection system utilizing the controller that could identify a single burned out lamp including identification of phase and color. It might have been very useful except for the advent of LED signal displays which made burnout detection totally obsolete. In 1988 I wrote a very detailed specification for this controller. My intent was the ultimate controller. Naztec did an outstanding job of providing all of the specified features by developing the 900 series controller. It is still possibly one of the most advanced controllers available.

There have been quite a few changes over the years. There are many other types, makes and models of traffic control devices. These are the main ones I have worked with over the years. Probably 80% of our intersections were part of coordinated systems. Most locations were 5-8 phases. This was true no matter which of the above systems were utilized. The last of the electro-mechanical controllers disappeared in the late 70’s. The last of the non microprocessor based controllers in the early 80’s. Our entire controller base was upgraded to the Naztec controllers in 1989-1990. Naztec controllers are still utilized though there have been a few upgrades and replacements.

This is how I remember it. It may or may not all be true but I’m sticking to the story until proved otherwise.