February 17, 2021
As many transportation agencies face insufficient funding to address vehicular congestion, signal timing optimization continues to evolve and grow in importance. In addition to saving motorists time, signal timing adjustments can improve safety by reducing the number of stops drivers make on daily commutes. Shorter travel times and fewer stops also reduce fuel consumption and air pollution.
However, signal timing can be complex and involve an unfortunate amount of fine-tuning in the field. Traditional signal timing methods require developing signal timing plans in Synchro, collecting turning movement counts, making adjustments in the field, and in some cases reoptimizing back at the office. The time and money agencies expend to obtain satisfactory results often cuts down the ROI of the effort.
Through a methodology built around the combination of three unique tools, Maricopa Association of Governments (MAG) in Arizona is improving its Signal Timing Optimization Program (TSOP). Keep reading to learn more about it, starting with an introduction to an app called TranSync.
TranSync: An Efficient Way to Optimize Signals
TranSync is an app that enables users to develop virtual signal timing plans in the office and then run the same timing plans on a mobile device in the field. Once signal timings are loaded into the app and clocks are synced with the controllers, TranSync will show what the signal indications should be showing at every point in time. Timing Adjustments do not have to be evaluated in the office but can be quickly assessed within the app. Additionally, TranSync enables staff to record video clips to use in before-and-after performance evaluations.
In 2016, MAG funded a project with the Arizona Department of Transportation (ADOT) and the City of Phoenix to study traffic signal timing at the I-17 interchanges with Indian School Road and Camelback Road in Phoenix. Indian School Road and Camelback Road are major east to west arterials that provide important east-west connection across I-17. The use of TranSync in developing several signal timing plans resulted in substantial reductions in travel time and delay for east-west travel. A before-and-after study conducted by an independent firm indicated that travel times were reduced by approximately 60% in the peak direction of travel on both corridors crossing I-17. Adding up the estimated time saved and its dollar value for a project, motorists are expected to save 350,000 hours of travel time, worth $6.2 million per year, because of this work.
Motorists are expected to save 350,000 hours of travel time on Indian School Road and Camelback Road, worth $6.2 million per year, because of signal timing optimization.
Combining TranSync With INRIX Data
TranSync is one piece of a cost-effective methodology that we have been excited to develop with the MAG Traffic Signal Optimization Program (TSOP), a program that provides vital traffic engineering assistance for refining signal operations across the MAG region. Building off the methods used in the Indian School Road and Camelback Road project, MAG has based its new performance evaluation guidelines on a combination of three tools: TranSync software, INRIX data, and a custom Performance Evaluation Spreadsheet.
INRIX probe data is collected daily from multiple sources, including commercial vehicles, connected automobiles, and mobile applications. It provides robust data that is quickly accessible through an online portal. INRIX has an agreement with the Federal Highway Administration (FHWA) and the Arizona State Departments of Transportation to provide traffic data for monitoring and measuring mobility performance at various levels.
The Performance Evaluation Spreadsheet is a custom tool we developed for MAG to calculate travel time improvements along the study corridors and report them in easy-to-use summaries. This spreadsheet calculates three reliability performance measures:
- Travel Time Index – this performance measure represents the average additional time required during peak times to travel the corridor as compared to times of light traffic.
- Travel Time Buffer Index – this performance measure represents the extra buffer time (or time cushion) that most travelers add to their average travel time when planning trips along the evaluated corridor to ensure on-time arrival.
- Planning Time Index – this performance measure represents the total travel time that should be planned for the evaluated corridor when an adequate buffer time is included.
More importantly, the spreadsheet also estimates the benefit/cost ratio to demonstrate the return that MAG is getting on every dollar spent on signal timing optimization in the region.
Case Study: Grand Avenue Signal Timing Optimization
Grand Avenue is a key state route that connects downtown Phoenix with the northwest metro area. The corridor posed several challenges, including atypical signalized intersections (within the study limits, half of the intersections are five- or six-legged intersections), a railroad crossing within 150 feet of intersections, and coordination required among four agencies: ADOT, City of Phoenix, City of Glendale, and City of Peoria. Due to this corridor’s complexity, previous signal timing optimization efforts resulted in long cycle lengths and high delay on cross-streets.
We were tasked with signal timing optimization for a 14-mile segment of Grand Avenue, including 19 signalized intersections.
To carry out this project, we began by developing a Synchro model and using it to develop draft timing plans. We then introduced a new approach by integrating TranSync and Inrix data. TranSync was used to optimize intersection offsets and verify consistency among the proposed plans and the actual timings. Additionally, it collected travel times and video of the corridor operations to assess the plans. INRIX data enabled us to monitor the corridor performance and provide a comprehensive before and after evaluation.
This project’s results, indicated in the performance evaluation spreadsheet, included improved traffic progression and reduced delay for vehicles approaching Grand Avenue, with much less time spent finetuning than if we were going in and out of the field to make adjustments. The benefit/cost ratio was 28.9, meaning for every dollar MAG spent, they got $28.90 in return.
The benefit/cost ratio of this signal timing optimization project was 28.9, meaning for every dollar MAG spent, they got $28.90 in return.
Future Applications
In summary, there is significant opportunity to improve the efficiency and ROI of signal timing efforts. We have found this combination of tools to be effective in cutting down efforts while increasing the efficiency of signal timing plans. Instead of the traditional methods requiring extensive data collection, we can pull robust probe data immediately into the program, make refinements from an tablet rather than from the office, and use the spreadsheet tool to provide a clear summary of information that agencies can use to evaluate how they want to move forward. We are grateful to work with agencies like MAG who are innovators in their methodologies, and believe this type of approach holds promise for agencies across the country.
To talk more about this work, feel free to reach out to me directly at fladron@kittelson.com.