What are all those roadway devices?

Not that I’m suggesting any distracted driving, but have you ever driven around and spotted what I call high-tech “highway hardware” and wondered exactly what it all does?

I was driving up Santa Fe the other day in Englewood and saw these two gnarly looking antennae pointing down at me from the traffic signal mast arm at Dartmouth Avenue. I knew antennae such as these were used to transmit data and control to signals where hard-wiring by fiber optic cable isn’t available.

But those are usually mounted high on a vertical pole off to the side. This was a double-array pointed right down at me as I waited for the light to turn green.

So I went out on a picture-taking expedition and then asked the Colorado Department of Transportation to give me the Dewars profile on these devices. Intelligent Transportation Systems experts Ken DePinto and Matthew Rickard provided the answers.

So it’s time to get all geeky with a picture primer on the roadside devices that are part of the effort to keep traffic moving both smoothly and safely.

Omni-Directional Antenna

Used for wireless communication link between devices or equipment. CDOT and other agencies use these antennas to transfer data between various traffic control devices such as traffic signals, ramp metering, school flashers etc. They are also used for some cell phone antennas to improve reception signal strength in remote locations (highway call boxes)

Red Light Activation Terminal

Its more common name is Tattle Tale Light. Indicates when a particular direction of a traffic signal is red. These units are installed and maintained by the local police agencies; they are attached to the signal wiring and will turn on a blue light when the traffic signal turns red for the direction that this unit is installed for. This allows the police department to sit beyond the signal while monitoring for red light runners. This keeps the police from needing to run the red light in order to pull over violators.

Emergency Vehicle Preemption Receiver

Also known as Opticom. It allows local emergency vehicles (Fire/ Paramedics) to preempt a traffic signal and turn opposing directions red and the direction of travel for the emergency vehicle green. Local fire departments install these units on traffic signals on major roadways to improve response time to emergencies. The fire department installs a special coded emitter device in their vehicles that trigger the Emergency Vehicle Preemption receiver on the traffic signal, changing the current operation of the signal and allowing the emergency vehicle to have a green light and proceed through the signal. ONLY Fire departments have use/ operation of this device, not even the police departments can use them.

Yagi Antenna

Used for wireless communication link between devices or equipment. CDOT and other agencies use these antennas to transfer data between various traffic control devices such as traffic signals, ramp metering, school flashers, etc. They are also used for some cell phone antennas to improve reception signal strength in remote locations such as roadside call boxes.

Red Light Activation Terminal

Another example of the “Tattle Tale Light.” Indicates when a particular direction of a traffic signal is red. These units are installed and maintained by the local police agencies; they are attached to the signal wiring and will turn on a blue light when the traffic signal turns red for the direction that this unit is installed for. This allows the police department to sit past the signal and monitor red light runners. This keeps the police from needing to run the red light to pull over a red light violator.

Panasonic Pan Tilt Zoom Camera (PTZ)

Full-function camera that can be controlled from a remote location. Used by various agencies to monitor road surface conditions, traffic volume, traffic incidents and any other situations in the range of the camera. Main use is to monitor traffic flow and alert drivers of possible slow down and or accidents. Capable of 360 degree pan, tilt and zoom functionality and low light image display. CDOT uses these devices to post images of road conditions on Cotrip.org.

2.4 GHz Planar Array Antenna

Used for wireless communication link between devices or equipment in areas where CDOT does not have fiber or hardwire communication available and can use the microwave system to send the data to a location that is connected to fiber or hardwire communication. Used by CDOT to transmit various types of data from one device to another in short spans from each other. It transmits data from traffic data collection equipment such as Side Fire Radar (SFR) units, Toll Tag Identifiers (TTI) and traffic counting loops. Also used to transmit video and control from a remote camera to a base unit.

Toll Tag Identifier (TTI) 916 MHz Yagi Antennas

Collects ExpressToll tag identification numbers. CDOT uses these devices to read the numbers, which are encrypted and can be matched from detection of the same tag at a different TTI location. Average vehicle speed and travel time can then be calculated from the matched tags. This data is combined with other traffic counting devices to produce Trip Travel Time messages and speed map alerts for traffic slowdowns.

Fixed Directional Tube Camera

This style of camera can do one of two things. Some models can perform vehicle detection and other models are just a fixed image camera with no control. Agencies use the camera for both applications. Traffic Detection Camera are used for traffic signal vehicle detection. They use the image from the camera to detect vehicle presence at an intersection, telling the signal controller that a vehicle is waiting for a green light or green left turn arrow. The fixed image camera is used for traffic management similar to the Panasonic pan tilt zoom camera, but the fixed tube has no control. It shows only the image it was aimed for at installation.

EIS RTMS Radar Device

RTMS units send out radar wavelengths and detect vehicles speed, size and how long it occupies an area. CDOT uses this device for various applications, most commonly traffic management. It works with the Toll Tag Identifiers/Wavetronix in calculating the flow of traffic in a specific stretch of roadway. This data is used to calculate trip travel times and alerts the Colorado Traffic Management Center of a slow section of roadway so it can advise of traffic problems. These devices are also used for traffic signal detection to indicate a vehicle is waiting for a green light. This device is also used for counting vehicle on a stretch of roadway for transportation planning. It records number of vehicles, types of vehicles (Semi-trucks, cars, box trucks, etc.), and if vehicles are slow in a stretch of roadway on a regular basis.

Wavetronix Radar Device

Uses digital wave radar for traffic detection, detect vehicles speed, size and how long it occupies an area. CDOT uses this device for various applications, most commonly traffic management. It works with the Toll Tag Identifiers/Wavetronix in calculating the flow of traffic in a specific stretch of roadway. This data is used to calculate trip travel times and alerts the Colorado Traffic Management Center of a slow section of roadway so it can advise of traffic problems. These devices are also used for traffic signal detection to indicate a vehicle is waiting for a green light. This device is also used for counting vehicles on a stretch of roadway for transportation planning. It records number of vehicles, types of vehicles (Semi-trucks, cars, box trucks, etc.), and if vehicles are slow in a stretch of roadway on a regular basis.

Read the full story at Kevin Flynn’s Inside Lane.

Longtime journalist Kevin Flynn was the transportation beat writer for the Rocky Mountain News.