SURTRAC Smart Traffic System

Millions of cars pass through a large city every day. This of course results in a large amount of traffic congestion and air pollution from engine emissions. One approach cities have taken to try and reduce traffic congestion is the installation of smart traffic signal control systems. These systems are designed to reduce congestion through smarter control of when traffic lights should be green or red. By using a computer to control traffic signals, congestion can be reduced.

The SURTRAC System

One system that is currently in use is called Scalable Urban Traffic Control or SURTRAC. This is an intelligent traffic signal control system developed by Rapid Flow Tech. They were a pilot program of the Traffic21 research institute of Carnegie Mellon University. Traffic21 is a research institute that is looking into how technology can help solve problems in transportation systems, especially those in the Pittsburg region. SURTRAC was led by Stephen Smith, a research professor at Carnegie Mellon, who eventually licensed the technology to create Rapid Flow Tech. SURTRAC was trialed in Pittsburgh, PA, and has since expanded to other cities.

The main idea behind SURTRAC is that it uses cameras, radar, and other sensors to detect vehicle activity at intersections and bases its decisions off how to best get vehicles through the intersection. There are 4 main steps:

1. Surtrac will use cameras or other sensors installed at intersections to determine what is going on.
2. Surtrac processes the information and creates a plan to optimize the traffic flow based on the current situation.
3. Surtrac will send commands to the traffic controller so that it can act on the plan.
4. Surtrac will finally send information to neighboring intersections so that they can factor that into making their own plans.

Overview of the Surtrac System. Source

Adaptability is one of the core ideas behind SURTRAC. The system is designed to be easily implemented and scalable. Surtrac is called a decentralized control system. Unlike other traffic control systems, there might be a central server that processes traffic data across the entire city and then makes decisions for all the city’s traffic signals, each Surtrac intersection will control its own traffic flow independently with only data about its neighbors. The benefit of this is that it is easy to implement and scale. A city can start with only a few intersections and gradually add more and more. Also, due to having to only process and optimize its own intersection, decisions can be made and updated in seconds to quickly adapt to changes in traffic.

SURTRAC can be integrated with nearly any type of traffic signal controller and vehicle detector. This means that cities can use their existing infrastructure with SURTRAC without the need to replace them. This again contributes to making Surtrac easier to setup than a centralized traffic control system.

SURTRAC turns optimization of traffic flow into a scheduling plan. Each intersection has a scheduler which will compute a schedule that minimizes the wait time for vehicles traveling through the intersection. At its most basic, it takes information from neighboring intersections as well as vehicle information from its sensors and runs that data through an algorithm that will determine the best timing of green and red traffic signals. For more detailed information, here is the study about the SURTRAC pilot program.

SURTRAC is also looking into improving safety and travel times for pedestrians. Bike and pedestrian options can be added to SURTRAC which could reduce travel times as well. The problem here is that there is not always a way to detect people and bikes in the same way there is for cars. This means there may not be a way to implement these features without adding new hardware.

Surtrac optimizes the timing of the signals at intersections for faster passing.

Surtrac Pros and Cons

Surtrac was installed at 9 intersections in Pittsburg in 2012. After a series of tests were conducted, it was concluded that the system provided great improvements over the existing system with an about a 25% decrease in travel times, 40% decrease in wait times, and 21% decrease in estimated vehicle emissions. These results were promising enough that Pittsburgh had installed SURTRAC at over 50 intersections by 2016 and stilled planned on adding more. The Department of Transportation (DOT) awarded Pittsburg $11 million to expand Surtrac to an additional 150 intersections across the city by 2020. (Just a side note: There are over 700 intersections in Pittsburgh according to this listing.)

Overall, SURTRAC has improved the traffic situation in Pittsburg. It has even done good for the environment by reducing emissions from vehicles because of its actions. What SURTRAC provides over other smart traffic systems is that its decentralized nature makes it easy to implement and scale. Due to the ease of integration with existing infrastructure, SURTRAC is also easy to implement. It also is faster at adapting to rapid changes in traffic due to its decentralized nature as opposed to more central systems.

SURTRAC was designed for dense urban traffic centers. There could be a chance it would not perform as well or that better options exist in less congestion areas. The decentralized nature of SURTRAC can potentially make it difficult to find out problems as opposed to a large, centralized network. A suboptimal performance of an intersection could be masked by the fact that it is just one node of many. There could be potential problems that arise out of the decentralized nature of the system. While neighboring nodes can communicate with one another, each intersection only really knows about its own area. This means it cannot see the big picture and make short sighted signaling decisions that might not be the most beneficial.

Thoughts on the Future of Smart Traffic Technologies

Smart traffic systems like SURTRAC have done a lot to reduce traffic congestion and travel times in modern cities. These systems rely on a combination of hardware and software to read oncoming traffic and make intelligent decisions about how to best time traffic signals. There are many systems like SURTRAC that have been tested and installed all around the world. A few examples include SCATS in Sydney, Australia and Sierra Transportation Technologies in the United States. As this technology improves it will be more and more widespread and hopefully greatly improve the transportation system.