1. OVERVIEW OF METHODS ESTIMATING ROADWAY EMISSIONS Rodney Langston February 24, 2004

2. EPA Approved Method for Estimating Entrained/Re-entrained Road Dust AP- 42 Emission Equation – Revision Published Nov. 2003 Applicable to Paved and Unpaved Roads Developed from Regression Analysis Utilizing 65 Samples

3. AP-42 Emission Equation E = k(sL/2)0.65 (W/3)1.5 - C where: E = PM Emission Factor Having Units Matching Units of k k = A constant dependent on particle Size and Emission Units sL = Road surface silt loading of material smaller than 75  m in g/m2 W = Mean Fleet Vehicle Weight in Tons C = Emission Factor for 1980’s Vehicle Fleet Exhaust, Break Wear, and Tire Wear

5. AP-42 Equation Issues No Mechanistic Basis – A Purely Statistical Model Formulation Wholly Dependent on the Data Set Derived From

6. AP-42 Equation Issues (Continued) Speed Not Accounted For  AP- 42 Equation Assumes 10-55 mph  Speed Is A Huge Factor in Emission Rate Silt Loading Measurements Required  Must Be Collected Manually  Requires Lane Closures  Process Costly – Limited Sampling Feasible

7. AP-42 Equation Issues (Continued) AP- 42 Equation Assumes A Stable Reservoir of Silt Loading  This Is A Physical Impossibility  Many Sources Contribute to Deposition Independent of Vehicle Entrainment  Emissions Estimates Increase In Direct Proportion to VMT  Makes Demonstrating Transportation Conformity or PM Attainment Very Problematic

9. Alternative Approach to AP-42 Vehicle Mounted Assessment Systems – Mounts Samplers on Vehicle Systems Have Been Developed by Desert Research Institute and University of California, Riverside

10. Desert Research Institute “TRACKER”

12. Testing Re-entrained Aerosol Kinetic Emissions from Roads (TRAKER) Front Top View Front Top View Front Side View Front Side View Background Monitor Influence Monitor

13. Sampling Plenum: Can Support Up To Five Sampling Instruments

14. TRACKER Instrumentation Particle Sensors  TSI DustTrack  Grimm Particle Size Analyzer GPS  Ashtech/Magellan Promark X Isokinetic System – Speed Independent

15. Data Acquisition and Processing Lab View program displays and logs data from 6 DustTraks, 3 Grimms, and 1 GPS Uniform time stamp applied to all data for consistent synchronization Data tables are loaded into MS Access for processing

16. Street Survey Data Logging

17. University of California, Riverside CE-CERT On-Board Particle Sensor System

18. CE-CERT Mobile Sensor System

19. Features of the CE-CERT System Samples Emissions Behind Tow Vehicle Adjustable Hitch – 1.4 m to 4.9 m Isokinetic Sampler Probes May Be Adjusted to Different Positions on Trailer

20. Vehicle Configuration

21. Schematic Diagram Isokinetic Sampling Probe

22. Emission Measurements Comparison DRI System Tested Extensively on Unpaved Roads in Idaho  More Calibration Work Needed for Paved Roads  Prototype System – Measured Higher Emissions Than Predicted by AP-42 Equation and Manual Silt Measurements on Paved Roads in Las Vegas

23. Emission Measurements Comparison (continued) CE-CERT System Tested on Paved Roads  Calibrated Emissions Measurements in General Agreement With, But on the Low Side, of Previously Reported Emissions Measurements  Measured Emissions Lower than AP-42 Methodology and California Silt Loadings

24. Advantages of Vehicle Mounted Assessment Systems Reduces Cost – Allows Expanded Sampling of Road Network Allows More Representative Sample Set – Eliminates Sampling Bias Does Not Require Lane Closures for Manual Silt Collection

25. Vehicle Mounted Assessment Systems (continued) Effective Tool for Evaluating Control Measure Effectiveness  Street Sweeping  Track Out Control  Road Improvements

26. Clark County DAQM & RTC Evaluation-Vehicle Mounted Systems Planning A Competitive “Drive Off” Evaluation of Available Systems Consultants will Operate Systems Over Fixed Course & Controlled Conditions RTC Consultant will Evaluate Data & Seek U.S. EPA Approval of Selected System as an Alternative to AP- 42

27. DISCUSSION