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How Can Smart Traffic Signal Help with Congestion?

To accommodate and support urban growth, one of the biggest challenges is managing congestion and improving traffic flow. Traffic jams are not only frustrating but also impact air quality. If you have ever driven in traffic, one of these scenarios might sound familiar to you: You are sitting at a red light in front of...

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Date

September 17, 2019

To accommodate and support urban growth, one of the biggest challenges is managing congestion and improving traffic flow. Traffic jams are not only frustrating but also impact air quality.

If you have ever driven in traffic, one of these scenarios might sound familiar to you:

  • You are sitting at a red light in front of the stop bar. The signal stays green on the other way even there is no traffic.
  • After waiting, you finally get a green light to go, but all the receiving lanes are still full. When the traffic starts to move, the light turns red again.
  • In order to turn right, you must yield to either the oncoming traffic or the crossing pedestrians, no matter if the light is red or green. It feels like you are stuck in the right turn lane forever.

What caused this inefficient traffic flow management? One of the crucial reasons is that the traffic signal timing cannot self-adjust with the live traffic conditions. The traditional way to control traffic lights is based on the pre-determined signal timing plan which is designed to accommodate a specific traffic flow pattern. Timing plans and time period boundaries are developed based on on-street observations and turning movement counts. As each pre-determined timing plan is activated by the time of the day, it is also called “time of day” operations.

In recent years, smart traffic signal technologies have been developed to improve signal timing efficiency. This new technology can detect and analyze the live traffic to produce the optimal signal timing plan which adapts to traffic demand in real time.

What do smart traffic signal systems need to work?

Detectors and sensors: Traditional traffic signals only have detectors in front of intersections while the smart traffic signals will need more upstream detectors and sensors to collect live traffic data for analysis.

Centralized computer system: A centralized computer system is needed to analyze data and manage traffic signal controllers at each intersection. Unlike the traditional “time of day” operations, the centralized system shall be monitored at all times and all the system issues must be addressed as soon as possible.

Communication network: A reliable communication network is required to exchange data between detectors, traffic controllers, and the centralized computer system.

Compatible Traffic Signal Controller: Each intersection will need to replace or retrofit the traffic controller to accommodate the smart traffic signal system

In Toronto, two smart traffic signal systems (SCATS and InSync) have been implemented across twenty intersections in North York and Scarborough. One of the smart systems, SCATS (Sydney Coordinated Adaptive Traffic System), was first developed in Australia where the majority of signalized intersections (around 11,000) are now SCATS operated. The InSync system was developed by Rhythm Engineering and has been operating at 2,300 traffic signals in the U.S as of November 2015.

Even with smart traffic signal technology, it will take time to make a decision on the most appropriate strategy for congestion management. For example, if the congestion is caused by saturated roadway capacity, smart traffic signals might not be the answer to this problem. More and more municipalities are turning to communication network infrastructure for roadway improvement projects, meaning efforts are being made to get our roads “smart” ready! We are excited to see how the technologies will evolve for our Smart Cities of tomorrow!


Yuqi is a civil engineer specialized in traffic signal and street lighting design with over 10 years’ experience.  Yuqi joined the IBI Toronto office in 2011 for VivaNext Rapid Transit Project and has been collaborating with IBI’s multi-disciplinary teams to deliver various municipal infrastructure design projects in Ontario such as roadway widening, AODA improvements, Transit Rapidway, bicycle lanes and multi-use trails.  Yuqi will be the traffic signal design lead for the Hurontario LRT project to commence in the fall of 2019.