Transcript Automobiles and the Environment, a Progress Report

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
Background
 AB 32
 AB 1493
 SB 375
2
Vehicle GHG Emissions
Pollutant
Environmental Concern
Carbon Dioxide (CO2)
Greenhouse gas
HFC-134a (from A/C system leaks)
Greenhouse gas
Methane (CH4)
Greenhouse gas
Nitrous Oxide (N2O)
Greenhouse gas
3
Greenhouse Gas Emissions
from Passenger Cars
(Assumes 27.5 mpg)
Source
Emissions
CO2-Equivalent
Emissions
Exhaust CO2 during CAFE Testing
322.48 g/mi
322.48 g/mi
Exhaust Methane
0.005 g/mi
0.12 g/mi
Exhaust Nitrous Oxide
0.006 g/mi
1.78 g/mi
Direct HFC-134a Emissions
0.007 g/mi
9.00 g/mi
“Indirect” A/C Emissions (CO2)
15.40 g/mi
15.40 g/mi
TOTAL
337.90
348.78 g/mi
CO2 as a Percent of Total
99.99%
96.87%
4
Historical and Projected Light-Duty Vehicle
Fuel Economy Standards
1978-2020
40
CAFE Fuel Economy Standard (mpg)
Passenger Cars
35
Light-Duty Trucks
Light-Duty Vehicles
30
25
20
15
10
1975
1980
1985
1990
1995
2000
2005
2010
2015
2020
Model Year
5
Range of Average Vehicle Class MPG
in 2006 Model Year
6
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
7
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
 ?
8
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

9
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)
10
The Effect of Speed on Gasoline
Powered Vehicle Emissions
3.5
ROG
CO
3.0
NOx
Emission Factor Relative to 45 mph EF
CO2
2.5
2.0
Per mile emission factors for all pollutants are lowest at
approximately 45 mph
1.5
1.0
CO2 curve is generally flatter at low & high speeds than HC,
CO & NOx
0.5
Source: EMFAC2007-derived factors for the calendar year 2007
0.0
20
25
30
35
40
45
50
55
60
65
70
Speed (m ph)
11
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)
12
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)

13
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
14
How are Statewide GHG Inventories
Currently Calculated?
 EMFAC based CO2 equivalent
 EMFAC based fuel consumption
 Adjustment for EMFAC vs. FHWA tax based fuel
consumption estimate
15
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
16