INRIX U.S. Signals Scorecard 2022 Annual Summary

Signal Demand and Performance Metrics Generation

The INRIX U.S. Signals Scorecard is created using four steps. The first three steps generate data that powers the INRIX Signal Analytics.^[1] The fourth step extracts and tailor’s data to create findings specifically for the Scorecard. These are the same steps followed in previous editions, with the exception that this edition is based upon 4 weeks of data spread throughout 2022, versus a single week previously.

Ingest sufficient, high-quality GPS data back to top

• INRIX has been ingesting anonymous GPS data from connected cars, commercial vehicles, and mobile devices since 2006.
• INRIX now ingests over 15 BILLION GPS readings daily in the United States alone.
• For Signal Analytics, INRIX analyzes over 85% of those readings from connected vehicles, with the best location accuracy and highest update rates. This ensures each individual vehicle’s movement in and around intersections can be analyzed with high confidence.
• For the four weeks utilized in this 2022 Scorecard, we leveraged more than 13.4 billion daily GPS readings.

Convert GPS readings into Trip Paths back to top

• INRIX Trip Analytics translates GPS readings into discrete trips, with origin, destination, route path, date and time stamps, etc. Data is cleaned, filtered, linked, ordered, and snapped to the road network to enable detailed analysis of trip path from start to end of each trip.
• INRIX Trip Analytics generates more than 130 million daily trips traversing over 1.25 billion miles in the U.S. each day, more than 10 billion miles overall in each week.
• INRIX curated over 1.16 BILLION highest quality trips covering more than 10 BILLION miles traveled across the U.S. over the four data collection weeks, to be used in Steps 3 and 4.

Generate Signal Performance Metrics. back to top

• INRIX Signal Analytics evaluates each individual trip as it moves through a known signalized intersection, creating a log of each vehicle/intersection interaction to enable aggregation of several metrics typically utilized to assess signal performance.
• Key information logged includes day/time stamp, turning movement, stops, and total travel time through the intersection.^[2]
• Signal Analytics presently covers over 253,000 signalized intersections in the U.S., with data at the movement, approach, and intersection level.
• Key for overall analysis and this Scorecard is that this approach enables analysis of all movements and approaches at an intersection and, over enough time, the random samples generated by the INRIX Signal Analytics Fleet will mirror overall demand and performance at the intersection.
• INRIX Signal Analytics aggregates metrics at the movement, approach, and intersection level for each intersection. For this Scorecard, data has been aggregated at the intersection level. The figure below illustrates how movement level metrics results in weighted average intersection level metrics.

Scorecard back to top

• Data was extracted in 15-minute increments for each intersection for the full weeks of March 21-27, June 13-19, September 19-25, and November 1-7, 2022 (a week in each calendar quarter). An average week was then created from these four weeks.
• Thus, for each metric, there were 672 different results (4/hour x 24 hours x 7 days) for each of 242,757 intersections across the U.S (signals for which data is available across all four weeks).
• Metrics extracted and used for this Scorecard are the number of observed vehicle crossings, average control delay per vehicle, arrival on green percentages, and split failure counts and percentages.
• INRIX Volume Profiles^[3] was used to estimate the penetration rate of the observed results at each intersection, to scale up results to represent total estimated intersection average daily traffic.
• Intersection scale factors enable total delay calculations and weighted averages for arrival on green percentage and delay/vehicle calculations for intersections rolled up by state, county and MPO.^[4]
• Data was extracted one state at a time and local time is used in all cases. When a state has more than a single time zone, the prevalent time zone is used for all data across the state (e.g., Florida is computed in Eastern Daylight Time).

https://inrix.com/products/signal-analytics/ An explanation of the processes used to create these metrics is here: https://docs.inrix.com/signals/metrics/ https://inrix.com/products/volume/ MPO boundaries were derived from this file: https://hepgis.fhwa.dot.gov/fhwagis/
Zipfiles/MPO_Boundary_01072022.zip

Signal Delay Emissions and Fuel Use Impact Estimation Methodology back to top

The FHWA Congestion Mitigation and Air Quality Improvement (CMAQ) Program released an Emissions Calculator Toolkit^[5] for use by agencies to estimate air quality benefits. As part of that toolkit, an intersection improvements module was created that uses the emissions rates from national level runs of the EPA Motor Vehicle Emission Simulator (MOVES).^[6] Leveraging the intersections module within the CMAQ toolkit, a green calculator was created to estimate the amount of fuel and CO₂ equivalents produced at signalized intersections due to idling.

The calculator uses the following:

• Assumed Fleet Year - Fleet year used in the EPA Moves Model
• Vehicle Volume - The amount of vehicles that cross an intersection or series of intersections
• Percentage of Heavy-Duty Trucks - The percentage of heavy-duty vehicles
• Initial Average Control Delay - The initial average delay vehicles experience as a result of the signalized intersection(s).
• Final Average Control Delay - The final average delay vehicles experience as a result of the signalized intersection(s).
• Urban or Rural Environment - The location of the signalized intersections of interest

The calculator uses these inputs to determine the following:

• Total Hours Saved - The total vehicle hours impacted by the change in average control delay. Mathematically this is the difference between the initial average control delay and the final average control delay, multiplied by the vehicle volume. This number can be scaled as a daily, weekly, monthly, or annual number.
• Carbon Dioxide Equivalents - The total number of hours saved is used along with the EPA MOVES emissions rates to determine the CO₂ equivalents.
• Total Fuel Savings - The total number of hours saved is used along with the EPA MOVES emissions rates to determine the energy consumption.

The process to estimate standard conversions between delay, emissions, and fuel consumes in the U.S. Signals Scorecard is based on the following assumptions.

• 3.24% Heavy Vehicles - Using the USDOT Bureau of Transportation Statistics approximately 3.24% of VMT outside of interstates could be considered 'heavy duty vehicles'
• 2023 Fleet - The 2023 fleet was used in the EPA MOVES model
• 1 gallon of fuel is equivalent to 120,286 BTU (US Energy Information Administration)

Using these assumptions, with the calculator methodology defined above, it was determined 1 hour of vehicle delay at signalized intersections in the U.S. would amount to 7.43 pounds of CO₂ and approximately 0.37 gallons of fuel.

Toolkit - CMAQ - Air Quality - Environment - FHWA (dot.gov)
Intersection Improvements Module - Toolkit - CMAQ - Air Quality - Environment - FHWA (dot.gov) Documentation of Emissions Data for the Traffic Flow Improvements Tool - Toolkit - CMAQ - Air Quality - Environment - FHWA (dot.gov)
MOVES and Other Mobile Source Emissions Models | US EPA

© INRIX, Inc. 2023