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Vince Bernardin, Jr.

Using GIS to Understand the Spatial Distribution of Mobile Emissions: An Alternative Approach to Air Quality Planning and Conformity Analysis. Vince Bernardin, Jr. Overview. What is air quality conformity analysis? What is AQ+? Why is it better than what we all do now? How does it work?

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Vince Bernardin, Jr.

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  1. Using GIS to Understand the Spatial Distribution of Mobile Emissions: An Alternative Approach to Air Quality Planning and Conformity Analysis Vince Bernardin, Jr. TRB Planning Applications Conference - May 7, 2007

  2. Overview • What is air quality conformity analysis? • What is AQ+? • Why is it better than what we all do now? • How does it work? • How difficult is it to use? • What can we do with it? • What’s next? TRB Planning Applications Conference - May 7, 2007

  3. What is this about? • It all comes from the Clean Air Act of 1970 (amended 1990 & by executive order). • Established National Ambient Air Quality Standards (NAAQS) • six “criteria” pollutants: • SO2, CO, NO2, Pb, O3, PM (10 & now 2.5) • Any area either “attainment” or “non-…” • Required State Implementation Plan (SIP) to achieve attainment TRB Planning Applications Conference - May 7, 2007

  4. What about transportation? • Mobile sources account for • About 50% of O3 precursors (Volatile Organic Compounds (VOC) and NOx) • About 90% of CO emissions • Also a significant contribution to fine PM TRB Planning Applications Conference - May 7, 2007

  5. Breath deeply • Therefore, the SIP includes “budgets” which impose a limit on the amount of each pollutant emitted in particular years from mobile sources from each non-attainment area. TRB Planning Applications Conference - May 7, 2007

  6. What’s “conformity”? • Every MPO in an non-attainment area is legally required demonstrate their long range plan (LRP) and transportation improvement plan (TIP) “conform” to the SIP (budgets). • hence, “conformity analysis” TRB Planning Applications Conference - May 7, 2007

  7. How’s it done? • The U.S. Environmental Protection Agency (EPA) mandates the use of its MOBILE6 emissions factor model. • MOBLE6 produces emissions rates per vehicle mile of travel (for each pollutant/precursor) • Vehicle miles of travel (VMT) are estimated by a travel demand model • Emission rate x VMT = Emissions TRB Planning Applications Conference - May 7, 2007

  8. How’s it (typically) done? • Emission rate x VMT = Emissions • This usually is done in a highly aggregate fashion - perhaps for each of a dozen or so functional classes of roadway - in a spreadsheet program. TRB Planning Applications Conference - May 7, 2007

  9. What is AQ+? • In a breadth: • A program to fully integrate MOBILE6 with a travel demand model in a GIS environment to allow the estimation and analysis of emissions at the link level TRB Planning Applications Conference - May 7, 2007

  10. AQ+: Key Features • Seamlessly combines travel demand model and MOBILE6 in an automated process • Computes emissions at the link level for improved accuracy • Produces regional emissions inventories • Produces link-specific emissions to enable air quality planning at the corridor level TRB Planning Applications Conference - May 7, 2007

  11. What is AQ+? TRB Planning Applications Conference - May 7, 2007

  12. AQ+: History 2003 - Initially developed for Evansville, IN and Lexington, KY 2004 - Adapted for use with the Knoxville, TN model 2005 - Major update for the Evansville version: running vs. non-running emissions, PM 2.5, multiple regions, & multiple seasons TRB Planning Applications Conference - May 7, 2007

  13. Does anyone care? “The tool has far exceeded the TPO’s expectations in terms of the level of air quality modeling capability that was envisioned to be achievable.” - Mike Conger, Knoxville Regional TPO “This is a very powerful easy-to-use tool to help streamline our transportation planning process. . . This module enables us to compare air quality conformity results with SIP budgets every time we test a scenario.” - Max Conyers, Lexington Area MPO TRB Planning Applications Conference - May 7, 2007

  14. Is it better? • In a word: Yes • More common spreadsheet style analysis require considerable aggregation of VMT • This aggregation introduces biases and inaccuracy because emissions rates are nonlinear • AQ+’s link-based disaggregate approach eliminates this aggregation error TRB Planning Applications Conference - May 7, 2007

  15. Example of Aggregation Error TRB Planning Applications Conference - May 7, 2007

  16. Example of Aggregation Error TRB Planning Applications Conference - May 7, 2007

  17. Is it better? Emissions Rates by Speed: Vanderburgh County, 2000 TRB Planning Applications Conference - May 7, 2007

  18. Example of Aggregation Error TRB Planning Applications Conference - May 7, 2007

  19. Example of Aggregation Error TRB Planning Applications Conference - May 7, 2007

  20. Example of Aggregation Error 34% Error! TRB Planning Applications Conference - May 7, 2007

  21. Aggregation Error • Errors can under or over predict emissions • Errors from aggregating over speed, time-of-day, facility type, etc. • Aggregation over speed alone results in underestimating emissions • But, aggregation over speed and time of day can lead to overestimation, depending on the region TRB Planning Applications Conference - May 7, 2007

  22. Aggregation Error • Thankfully, the law of large numbers helps and there is considerable canceling of errors • Typical errors at the county level have generally been on the order of 5% • However, errors in the calculation of impacts can be considerably larger TRB Planning Applications Conference - May 7, 2007

  23. Example of Aggregation Error TRB Planning Applications Conference - May 7, 2007

  24. Example of Aggregation Error TRB Planning Applications Conference - May 7, 2007

  25. Emissions Rates Emissions Rates by Speed: Vanderburgh County, 2000 TRB Planning Applications Conference - May 7, 2007

  26. Example of Aggregation Error 13% Error TRB Planning Applications Conference - May 7, 2007

  27. Example of Aggregation Error 300% Error! TRB Planning Applications Conference - May 7, 2007

  28. Aggregation Error • IMPORTANT IMPLICATIONS • the traditional aggregate approach will tend to underestimate emissions benefits of speed improvements - even to the point of showing false disbenefits TRB Planning Applications Conference - May 7, 2007

  29. Aggregation Error • An experiment using a proposed new freeway showed increased VOC by either method, but the traditional aggregate methodology showed a 23% higher increase in emissions than the disaggregate approach in one county TRB Planning Applications Conference - May 7, 2007

  30. How does it work? • Step 1: Volumes and speeds • Link speeds and volumes by time of day (AM, PM, OP) are taken from the travel demand model • Distributions are used to disaggregate volumes and generate average speeds for each hour • VMT is apportioned into upper and lower speed bins taking the average as the harmonic mean TRB Planning Applications Conference - May 7, 2007

  31. How does it work? • Step 2: Calculation of emissions rates • AQ+ runs MOBILE6 for each: • County (vehicle fleet mix, climate, etc.) • Time of year (July, summer, winter) • Facility type (freeways, arterials, locals, ramps) • Speed bin (14) • For the Evansville region, for each AQ+ run, 270 MOBILE6 scenarios are run generating as many as 17,820 emission factors TRB Planning Applications Conference - May 7, 2007

  32. How does it work? • Step 3: VMT adjustments and application of emissions rates • Factors are applied to bring the total VMT for each facility type for each county into line with HPMS estimates • For freeways and arterials, emissions rates by speed are applied for each hour on each link • Emissions rates for locals & ramps are applied to their adjusted total VMT TRB Planning Applications Conference - May 7, 2007

  33. How does it work? • Step 4: Reporting emissions • AQ+ generates an emissions inventory report to facilitate easy conformity determinations for each region in the area • AQ+ writes the running emissions on each link to network fields for easy display, map making and further analysis TRB Planning Applications Conference - May 7, 2007

  34. How difficult is it to use? • Not difficult at all - the computer does all the work • Graphical user interface • No manual calculations • Easier than spreadsheet methods TRB Planning Applications Conference - May 7, 2007

  35. Step 1: General Settings TRB Planning Applications Conference - May 7, 2007

  36. Step 2: Seasonal Inputs TRB Planning Applications Conference - May 7, 2007

  37. Step 3: Regional Inputs TRB Planning Applications Conference - May 7, 2007

  38. Step 4: Run Options TRB Planning Applications Conference - May 7, 2007

  39. Conformity Report TRB Planning Applications Conference - May 7, 2007

  40. Link by Link Emissions TRB Planning Applications Conference - May 7, 2007

  41. Easy Map Making TRB Planning Applications Conference - May 7, 2007

  42. Corridor Level Analysis TRB Planning Applications Conference - May 7, 2007

  43. Corridor Level Analysis • Air quality was considered in the decision to increase speed limits in one corridor in Evansville • Last fall, state air quality officials in Indiana indicated the appropriateness of AQ+ as a method of identifying / prioritizing CMAQ projects to target problematic corridors in an MPO TRB Planning Applications Conference - May 7, 2007

  44. What’s Next? • Further flexibility of inputs • Emissions rates by time-of-day • Node (intersection) emissions • Looking ahead to MOVES TRB Planning Applications Conference - May 7, 2007

  45. QUESTIONS? TRB Planning Applications Conference - May 7, 2007

  46. THANK YOU! TRB Planning Applications Conference - May 7, 2007

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