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Full circle with the U-turns: Traffic Signals in Metro Manila

October 2010
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Since last week, it seemed as if a ghost of Christmas past has come to haunt me and my colleagues at the NCTS. We had some unexpected visitors from the Traffic Engineering and Management (TEAM) group of the Department of Public Works and Highways (DPWH). They were at the Center to consult about a project being formulated by the group together with the MMDA for new traffic signals for Metro Manila. DPWH-TEAM has a long history with NCTS starting when that unit was created when the Philippines invested on its first coordinated traffic signals in the 1970s.

At that time, the NCTS was still the Transport Training Center (TTC), and was the site of the first traffic control center for signals that were installed along Quezon Avenue. The package was funded by a loan from the Japanese government and hence involved traffic signals manufactured by Mitsubishi. Years and many TEAM project phases later, most of Metro Manila’s major intersections would be signalized and traffic signal control would be under the Traffic Engineering Center, which until 2003, was under the DPWH. In the 1990’s, the TEC and TEAM worked together to acquire the Sydney Coordinated Adaptive Traffic System (SCATS), which at the time was already installed and running in most major intersections in Cebu City.

SCATS was supposed to usher in a new era in traffic control in Metro Manila until some major problems eventually plagued its operation. One of these problems was power. However, this was something everybody else was concerned with because of the power crisis of the early 1990s. It was also something that seemed to be easily solvable with the acquisition and installation of uninterrupted power systems (UPS) and generators that allowed the facility to operate even during blackouts.

Another technical problem cropped up just about the same time when the TEC and TEAM people were trying to solve the power issue. This time, it was something much more complicated and perhaps, what led to the system losing its credibility in Metro Manila and a chain reaction of sorts in as far as reactions go. The communications problem was a critical one and rendered the system practically unreliable for what it was supposed to solve – congestion. SCATS required a reliable network for its controllers and computers to communicate with each other. This communication allowed its software to assess network-wide traffic demand measured by means of detectors embedded in the pavement at each approach lane of an intersection. Data from these detectors are transmitted to computers in the control center, which then compute for  the optimum cycle times for each signalized intersection. The computers determine which intersections need to be coordinated and how (i.e., alternating or simultaneous), and this process allows SCATS to adapt to variations in traffic. Hence, its name which seemed only appropriate given its performance in what is now the expanded network in metropolitan Cebu.

The failure of SCATS in Metro Manila was further hastened by traffic enforcers who were only too eager to intervene. This intervention was more of interference as enforcers started switching the traffic signal controllers to manual mode at the slightest indication that the signals would appear to be non-responsive to changes in the traffic situation. In truth, it takes a few minutes for the detectors to collect data and send it to the computers that will compute for the appropriate cycles and signal settings as well as determine which intersections to “marry” and “divorce” – to borrow terms used by traffic engineers in Cebu City for the process of coordinating intersections throughout the day. Due to this rampant practice by enforcers in Metro Manila, it was only a matter of time before SCATS was declared a failure and claims were made that Metro Manila traffic is so much more complicated than Cebu’s, where SCATS was a success (it still is today).



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