It’s Easy to Quantify Changes in GHG Emissions from Cars and Light Trucks – Right? Presented to: SACOG Panel Discussion April 16, 2009 Presented by: Bob Dulla Sierra Research

2 Background AB 32 AB 1493 SB 375

3 Vehicle GHG Emissions PollutantEnvironmental Concern Carbon Dioxide (CO 2 )Greenhouse gas HFC-134a (from A/C system leaks)Greenhouse gas Methane (CH 4 )Greenhouse gas Nitrous Oxide (N 2 O)Greenhouse gas

4 Greenhouse Gas Emissions from Passenger Cars (Assumes 27.5 mpg) SourceEmissions CO 2 -Equivalent Emissions Exhaust CO 2 during CAFE Testing g/mi Exhaust Methane0.005 g/mi0.12 g/mi Exhaust Nitrous Oxide0.006 g/mi1.78 g/mi Direct HFC-134a Emissions0.007 g/mi9.00 g/mi “Indirect” A/C Emissions (CO 2 )15.40 g/mi TOTAL g/mi CO 2 as a Percent of Total99.99%96.87%

5 Historical and Projected Light-Duty Vehicle Fuel Economy Standards

6 Range of Average Vehicle Class MPG in 2006 Model Year

7 Key Points All vehicles within the same class/model year meet the same criteria pollutant standard Substitution of a small car for a large car has no impact on criteria pollutant emissions Wide diversity in fuel economy (GHG) emissions within same class/model year Substitution of a small car for a large car can significantly reduce GHG emissions Tracking GHG impacts of vehicle substitution requires more detailed information

8 Transportation Options to Reduce GHGs Signal timing improvements Increased carpooling Trip reductions Increased use of transit Greater utilization of existing fuel efficient vehicles Changes in land use Vehicle scrappage ?

9 Traditional Metrics Used to Quantify Motor Vehicle Emissions Travel Models Supply  Trips (starting and evaporative emissions)  Link specific VMT (running emissions)  Link specific speed (running emissions) EMFAC Supplies  Emission rates (g/trip or g/mi) by vehicle class and model year  Correction factors (e.g., speed, temperature, etc.)  Relative share of travel across vehicle classes

10 What Does EMFAC Supply for GHG Calculations? GHG emission rates (g/mi) by vehicle class and model year Speed correction factors for portions of the vehicle fleet Travel activity data (consistent with MPO projections)

11 The Effect of Speed on Gasoline Powered Vehicle Emissions

12 What is Missing? No subclass specific GHG values No forecast of fleet improvements (e.g., CAFE or AB 1493) No GHG speed correction for most HDVs (only HHDDVs)

13 GHG Control Measures that Cannot Be Quantified Increased utilization of fuel efficient vehicles  Shift from truck to car can be quantified  Shift from large car to small car cannot All measures in future years (no forecast of CAFE improvements)

14 What’s Needed to Address this Shortfall? Forecast of annual changes in GHGs by vehicle class Distribution of GHGs within vehicle class/model year Vehicle class specific speed correction factors Information on household vehicle mix

15 How are Statewide GHG Inventories Currently Calculated? EMFAC based CO 2 equivalent EMFAC based fuel consumption Adjustment for EMFAC vs. FHWA tax based fuel consumption estimate

16 Issues to Consider in Estimating GHG Emissions How well do average annual weekday travel estimates translate to annual estimates of GHG emissions?  Weekday vs. weekend  Heavy truck travel activity  Household vehicle utilization rates Can or should GHG emission estimates be developed within the criteria pollutant framework? Is local fuel use ever used to assess or validate local travel estimates? Need for MPO/ARB GHG model coordination