A decentralized adaptive signal control system could reduce fuel consumption by 4.3 million gallons and total emissions by 39K tonnes annually, if deployed city-wide in Pittsburgh.

Results of a real-time, decentralized traffic signal system pilot test in Pittsburgh, PA.

July 2012
East Liberty,Pittsburgh,Pennsylvania,United States

Summary Information

The Robotics Institute at Carnegie Mellon University (CMU) developed an adaptive traffic signal control system, SURTRAC (Scalable URban TRAffic Control), designed specifically for urban road networks, where there are multiple, competing dominant flows that shift dramatically based on time of day. This system is a decentralized system, where each signal independently determines its phasing based on incoming vehicle flows and projected outflows from neighboring signals.

In order to test this system, a pilot of nine intersections in the East Liberty area of Pittsburgh, Pennsylvania was equipped with this technology for a before and after study to analyze the difference in performance for the existing and SURTRAC systems. The test area has an average daily traffic volume of nearly 30,000 vehicles per weekday.

To evaluate the SURTRAC system's performance, a series of timed, drive-through runs of the pilot test were conducted both under existing conditions and with the SURTRAC system enabled. The twelve highest volume routes through the East Liberty pilot test site were chosen for analysis. Tests were conducted for four weekday time periods -- AM-Rush, Midday, PM-Rush, and Evening -- in order to test the performance of the system in multiple conditions. "Before" testing was conducted in March 2012 and "after" testing was conducted in June 2012, with slightly higher (roughly 5%) traffic volumes in June.

Based on reductions in wait times, number of stops and travel times, the CMU team estimated reductions in motor fuel consumption, as well as five types of emissions. The team projects that city-wide expansion could save the city's drivers over four million gallons of fuel and prevent the release of over 39,000 tonnes of emissions annually.

The projected fuel and emissions savings can be found in Table 7 below. The daily and annual figures are calculated for the nine intersections within the test site based on daily vehicle estimates and 261 weekdays per year. These savings are then projected at the city-wide level, assuming that the level of benefit per SURTRAC enabled intersection remains constant as the system expanded to cover all 600 intersections in the City of Pittsburgh.

Fuel Consumption247 gal.64,580 gal.4,305,353 gal.
Carbon Dioxide (CO2) Emissions2253 kg557.8 tonnes38,521 tonnes
Carbon Monoxide (CO) Emissions17.3 kg4.5 tonnes301 tonnes
Nitrogen Oxides (NOx) Emissions3.4 kg0.9 tonnes58 tonnes
Volatile Organic Compounds (VOC)4 kg 1.0 tonnes70 tonnes
Hydrocarbons14.9 kg3.9 tonnes259 tonnes
Total Emissions2253 kg588 tonnes39,209 tonnes
Table 7: Projected Emissions Savings


See also:
Scalable Urban Traffic Control (SURTRAC) - CMU Project Page

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Real-Time Adaptive Traffic Signal Control for Urban Road Networks: The East Liberty Pilot Test

Author: Stephen F. Smith, Gregory J. Barlow, Xiao-Feng Xie, Zachary B. Rubinstein

Source Date: July 2012



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Typical Deployment Locations

Metropolitan Areas


traffic signals, adaptive signals, adaptive signal control, ASC, decentralized signal control, real-time signal control

Benefit ID: 2013-00821