Traffic management can be one of the more expensive and complex issues facing municipal managers. And if something goes wrong, the town or city is sure to hear about it. Even simple traffic systems can be difficult to monitor, maintain, and repair.
Without clear visibility into the status of each traffic light’s control box, lights can fail before municipal managers are aware, risking collisions and expensive repairs. So, municipal managers turn to SCADA traffic control monitoring to keep their traffic flowing smoothly.
Supervisory control and data acquisition, or SCADA, allows municipal employees to monitor the status of their traffic lights, whether there are two in town or two million.
Supervisory control and data acquisition, or SCADA, allows municipal employees to monitor the status of their traffic lights, whether there are two in town or two million. SCADA itself isn’t a product—it’s a concept—a system in which distant pieces of hardware communicate with a central node.
SCADA enables employees to watch and, in some cases, control every traffic light in the city from the same chair. Depending on the municipality, different SCADA traffic control strategies can be used to improve traffic flow, reduce malfunctioning lights, and lower maintenance costs.
Simple SCADA Traffic Control Monitoring
The simplest and most direct application of the SCADA concept to municipal traffic control is system monitoring, which—more specifically—is a system of effective equipment monitoring.
Traffic lights have equipment cabinets, usually located at their feet or corners of intersections. If the equipment in the cabinet is working, so is the traffic light.
By monitoring equipment cabinets, municipalities can:
- See when a traffic light goes down.
- Detect a traffic light failure before it happens.
- Repair a traffic light before it fails, heading off collisions in an uncontrolled intersection.
- Make sure networks are up and running for first responders in the event of an emergency.
So how is it done? By adding a monitoring device, known as an RTU (remote terminal unit) to each equipment cabinet—RTUs can track environmental conditions inside equipment cabinets, warning municipal managers if temperature or humidity threatens the operation of traffic lights.
RTUs can track environmental conditions inside equipment cabinets, warning municipal managers if temperature or humidity threatens the operation of traffic lights.
RTUs can be used to detect other issues, such as flooding, unauthorized physical entry, or voltage deviations. If an issue is detected, RTUs transmit the information to the appropriate responder. This represents the “Data Acquisition” portion of SCADA.
Increasing Complexity in SCADA Traffic Control Monitoring
For small traffic grids—with a dozen lights or less—RTUs can directly inform the maintenance crew leads of problems. Once grids become larger and more complex than this, it becomes more efficient to route alarms to a master station.
A central master station sorts, prioritizes, and informs dispatchers and managers of problems by order of importance.
Large cities may further subdivide their traffic grids into multiple regions—each watched over by an individual master station. This allows regions to deal with problems locally. By transmitting information to a central master station—which displays it in a browser—city-level managers can:
- Enjoy total system oversight.
- Use centralized data to plan strategically.
- Respond tactically to widespread emergent situations like earthquakes or hurricanes.
This represents the “Supervisory Control” portion of SCADA:
Supervisory control visibility gives managers time to dispatch maintenance services to correct the problem. Situations to consider include:
- Overheating of Equipment. If equipment is overheating, technicians can be sent to repair or install HVAC equipment. Police are dispatched when there’s unauthorized entry.
- Flooding or Natural Disasters. For flooding and other natural disasters, SCADA provides the added benefit of a working real-time, street-level map, which can inform emergency services and establish a historical record.
- Emergency Telecom Equipment. If emergency telecom equipment is also located in traffic control equipment cabinets, the RTUs can monitor those communications as well.
Enhanced Supervisory Control in SCADA Traffic Management
SCADA architecture is like the Roman roads—they all go to Rome. As described previously, anything that happens in the network transmits to a central control station: “Rome.”
Well, roads go two ways. In more advanced SCADA systems:
- The flow of information can be reversed.
- Commands from central control are obeyed by equipment dispersed throughout the city.
- Commands are issued to the RTUs themselves. For example:
If summer heat threatens equipment function, the RTU can be commanded to turn on the AC. But once the roads have been laid and the network architecture is in place, commands can also go to the traffic lights themselves.
RTUs within a SCADA system allow city managers to alter traffic patterns at need, in response to accidents, large events like concerts, or dangerous situations like a fire or flood. This is another facet of the “Supervisory Control” portion of SCADA.
SCADA and Emerging Traffic Control Technology
While central traffic control may sound appealing, in reality, responding to changing traffic needs at every light 24/7/365 takes more employees than can possibly be assigned. At that point, the city might as well just give up on traffic lights and send policemen with flags and radios to every intersection. So, traffic patterns are largely automated with emerging technologies as outlined below.
- Visual, Radar, and LIDAR Recognition Systems. The latest in traffic management is the deployment of visual, radar, and LIDAR recognition systems to count vehicles at each intersection. Vehicle-to-infrastructure communication will follow.
- Smart Traffic Control. Some trends are overwriting the use of pressure plates although many municipalities still use legacy systems. Programmable Logic Controller (PLC) technology measures traffic density by the number of vehicles and weight sensors. Then, traffic lights react accordingly to help control the congestion and flow of traffic.
- Keeping an Eye on Artificial Intelligence (AI). Whether visual or somatic, these tracking systems inform all traffic controllers. Controllers can then adjust lights and traffic patterns as needed, based on historical patterns and the current situation.
In this instance, SCADA is used to keep an eye on artificial intelligence (AI). While not actively changing traffic patterns themselves, retaining the ability to do so and override AI decisions helps city managers prevent or reverse unwise decisions made by autonomous-thinking machines.
With all the added hardware involved in AI control—like cameras, pressure plates, and the computers themselves, RTUs become even more important.
With all the added hardware involved in AI control—like cameras, pressure plates, and the computers themselves, RTUs become even more important. RTUs help monitor and maintain the functionality of simpler SCADA systems. RTUs also enable managers to receive alarms about potential problems and dispatch technicians to repair hardware issues.
The Benefits of SCADA and RTUs in Traffic Control and Automation
By using SCADA architecture and implementing a traffic control monitoring system of RTUs, municipalities can reduce costs and improve service. Traffic flow improves, repair costs are lowered, and accidents are prevented through monitoring and automation.
Image courtesy Unsplash, Roberto Junior