Like many agencies, the Utah Department of Transportation (UDOT) has concluded that it cannot always build its way out of transportation problems. Innovation, creativity, risk, and increased transparency are necessary to meet a growing society’s transportation needs.

In 2011, UDOT senior leaders challenged the traffic signal program to become “World Class” because of the large return on investment it expected from improved signal operations. Performance measurement, which historically has been a labor intensive and cost prohibitive means of gathering data, was identified as a necessary component of a world class signal operation.

About this same time, UDOT partnered with Dr. Darcy Bullock, professor of Civil Engineering at Purdue University and director of the Joint Transportation Research Program who, along with the Indiana Department of Transportation (INDOT), pioneered the efforts of real-time traffic signal performance measures outside of proprietary central traffic management systems. Purdue University and INDOT accomplished this goal by defining various enumerations and working with signal controller manufactures to provide a data logger built into controller firmware to collect high-resolution data. A file transfer protocol (FTP) connection is made frequently from a central server to the traffic signal controller to retrieve the data files. Once collected, the data files are translated into a database, where they are used to generate a series of visual metrics and archived for comparative analysis.

UDOT staff wrote an Automated Traffic Signal Performance Metrics (SPMs) program and a web interface with over a dozen metrics. The website does not require special software or firewall permissions so everyone has the opportunity to view the information, thus helping UDOT reach one of its goals of increased transparency. UDOT’s SPM website is at: http://udottraffic.utah.gov/signalperformancemetrics/. SPMs include visual displays such as: the actual time used by each phase, the percentage of vehicles arriving on green and red, turning movement volume counts, the frequency of pedestrian actuations, green time failure, how various approaches terminate when the light changes from green to yellow, and summary reporting.  SPMs can also be used to determine whether detectors are working properly. The program generates daily emails about potentially problematic locations so technicians can fix the malfunction before the public is significantly inconvenienced, helping UDOT meet their goal of being proactive instead of reactive. In addition, the SPMs can operate as a human-in-the-loop adaptive system, helping to maintain timing plans more effectively.

As with most new processes and technology, there are some challenges.  SPMs require resources to set up, calibrate and troubleshoot; a large amount of server storage is needed to archive the data; and additional records are created that may be subject to subpoenas. However, the advantages that SPMs provide far outweigh the challenges.

With this technology, UDOT has used its resources more effectively to improve mobility and increase safety. SPMs have changed standard operating procedures for their signal retiming process. Signal timings are now updated more frequently and more accurately than before. UDOT no longer relies solely on limited snapshot-view retiming methods using manual data collection and traffic models to optimize traffic signals and signalized corridors. UDOT now directly measures what previously could only be estimated and modeled.

AASHTO awards a few Group Focus awards each year to transportation organizations that utilize innovative technologies that have the potential to modernize the industry. Impressed with the technology behind SPMs, UDOT was awarded one of three 2013 Group Focus awards, which gave UDOT the opportunity to share innovations, ideas and successes with other agencies. To help promote adoption of the technology, UDOT’s SPM software is available for free to other agencies, vendors, and consultants. As of September 2015, ten agencies in nine states are using SPMs, and in Utah alone, SPMs are active at 1500 of the states 1950 traffic signals.