Emissions

					Fuel Consumption
                          Data Consistency
• “Number of vehicles”, “miles        • “Emissions” data given in
  driven”, and “fuel consumption”       four categories by EPA:2
  data given in six categories by the
  FHWA:1                                 – Light Duty Gas Vehicles and
   –   Passenger Cars                                   Motorcycles (LDGV&MC)
   –   Buses                                          – Light Duty Gas Trucks (LDGT)
   –   Motorcycles                                    – Heavy Duty Gas Vehicles
   –   Other 2-Axle, 4-Tire Vehicles                    (HDGV)
   –   Single Unit Trucks                             – Diesels
   –   Combination Trucks

  Categories from FHWA converted to EPA Categories through:3

  •LDGV&MC = .9864 (Passenger Cars) + Motorcycles

  •LDGT = .9918 (Other 2-axle, 4-tire vehicles)

  •HDGV = .1028 (Buses) + .7994 (Other Single Unit Trucks)

  •Diesels = .0136 (Passenger Cars) + .0082 (Other 2-axle, 4-tire vehicles) + .8972 (Buses)
  +.2006 (Other Single Unit Trucks) + 1.0000 (Combination Trucks)
   Comparison between Fuel Consumption and
             Miles Driven Trends
                                   Fuel Consumption                                                                             Miles Driven

                                                                                            3,000,000
  180000
  160000                                                                                    2,500,000

  140000                                                                                    2,000,000
  120000
                                                                                            1,500,000
  100000
   80000                                                                                    1,000,000

   60000                                                                                     500,000
   40000
                                                                                                   0
   20000




                                                                                                    70

                                                                                                    72

                                                                                                    74

                                                                                                    76

                                                                                                    78

                                                                                                    80

                                                                                                    82

                                                                                                    84

                                                                                                    86

                                                                                                    88

                                                                                                    90

                                                                                                    92

                                                                                                    94

                                                                                                    96

                                                                                                    98

                                                                                                    00

                                                                                                    02
                                                                                                  19

                                                                                                  19

                                                                                                  19

                                                                                                  19

                                                                                                  19

                                                                                                  19

                                                                                                  19

                                                                                                  19

                                                                                                  19

                                                                                                  19

                                                                                                  19

                                                                                                  19

                                                                                                  19

                                                                                                  19

                                                                                                  19

                                                                                                  20

                                                                                                  20
       0
       1965       1970      1975     1980   1985     1990      1995       2000       2005               Total                             Light-Duty Gas Vehicles & Motorcycles
                                                                                                        Light-Duty Gas Trucks             Heavy-Duty Gas Vehicles
           Total                                   Light-Duty Gas Vehicles & Motorcycles
           Light-Duty Gas Trucks                   Heavy-Duty Gas Vehicles                              Diesels
           Diesels




•Dips in “miles driven” (1974, 1978-1980 total; 1990-1994 LDGV&MC) correspond to
decreases in “fuel consumption” but there are additional dips and longer dips in “fuel
consumption” (1974 -75, 1978-1984, 1989-1992 total; 1990 - 2002 LDGV&MC).

•Thus, there is not a one-to-one correlation between “miles driven” and “fuel consumption”
      MPG per Model Year5 Compared to National
                Vehicle Fleet MPG
                          FIGURE 1                                                        Miles Per Gallon Trend
       FUEL ECONOMY OF U.S. VEHICLES BY MODEL YEAR
                                                           25



                                                           20



                                                           15




                                                     MPG
                                                           10



                                                           5



                                                           0
                                                           1965        1970      1975        1980    1985      1990      1995         2000     2005

                                                                  HIGHWAY VEHICLES (Tier 1 - 11)            Light-Duty Gas Vehicles & Motorcycles
                                                                  Light-Duty Gas Trucks                     Heavy-Duty Gas Vehicles
SOURCE: EPA                                                       Diesels




•Increase in fuel economy for MY 1975-86 vehicles corresponds to the increase
in national vehicle fleet fuel economy from 1980 to 1991
•Leveling off of national vehicle fleet fuel economy after 1991 corresponds to
slight decrease in fuel economy after 1986
•Lag occurs because vehicle turnover is not instantaneous (average vehicle
age is 7-8 years)6
       Fuel Consumption Summary

• Fuel consumption trends are the result of a competition between
  vehicle use and fuel economy.

• Vehicle use depends on many factors, including traffic congestion
  and personal driving habits. However, “miles driven” shows that the
  general trend is an almost continuous increase.

• Increases in the national vehicle fleet fuel economy create short
  reductions in ”fuel consumption”, but the near continuous increase
  in “miles driven” causes the “fuel consumption” to trend upward
Emissions
            Important Emission Improvements
•   1968 – Tailpipe emission standards first implemented for new cars to reduce VOC
    and CO emissions.6

•   1970 – Congress passes the Clean Air Act which calls for a 90% reduction in
    emissions by 1975. This deadline is later extended to 1980 for VOC and 1981 for
    NOx and CO emissions.7

•   1971 - New cars have to meet evaporative emission standards for the first time and
    charcoal canisters are introduced to collect VOC vapors.7,8

•   1972 - Exhaust gas recirculation valves are implemented to reduce NOx emissions.7
•   1975 – Most new cars have catalytic converters to reduce VOC and CO emissions.8
    Unleaded gasoline introduced (with a 13% market share) since lead inactivates the
    catalytic converters. Market share climbs to 50% in 1982 and 100% in 1996.9

•   1980/81 – In response to implementation of CAA emission standards, new cars are
    equipped with three-way catalysts that optimize the efficiency of catalytic converters
    and reduce NOx emissions.7
•   1983 – Passenger Vehicles are first required to undergo testing for “malfunctioning
    emission control systems”.7
•   1990 – CAA Amendments passed including increasing testing requirements.7 Limit
    on diesel fuel sulfur content (to reduce SO2 and PM emissions) is set by EPA to take
    effect in 1993.9
•   1991 – Lower tailpipe standards set for VOC and NOx emissions to be phased in
    beginning in 1994.7 NOx emissions standards for new trucks and buses cut in half.10
•   1992 – Limits for CO emissions at cold temperatures are set to be phased in
    beginning in 1994.7
•   1993 – The Diesel PM standard for urban buses is reduced. This standard is further
    reduced in 1994 and 1996.11
•   1999 – SUV’s subject to same emissions standards as other vehicles for the first
    time. More restrictive standard for VOC, CO, NOx, and PM begin to be phased in
    (end 2008).7 Standard for sulfur content in gasoline is reduced to take effect in
    2005.12
•   2000 –Standard for sulfur content of diesel fuel is again reduced to be phased in
    between in 2007 – 2010. By cleaning up the fuel, emission control technologies can
    finally be implemented in Diesel vehicles.13
                                                    CO Emissions
                           CO Emission

180,000
                                                                         •   Overall emission trends determined by
160,000                                                                      LDGV&MC emission trends
140,000
120,000
100,000                                                                  •   Lower emissions for HDGV, LDGT,
 80,000                                                                      and Diesels because of less use, as
 60,000
 40,000                                                                      shown in “miles driven”.
 20,000
     0
     1965   1970    1975    1980    1985   1990    1995    2000   2005
                                                                         •   The effect of the increase in LDGT use
                                                                             is minimized because the increase
                   HIGHWAY VEHICLES (Tier 1 - 11)
                   Light-Duty Gas Vehicles & Motorcycles
                   Light-Duty Gas Trucks
                                                                             comes a few years after the emissions
                   Heavy-Duty Gas Vehicles
                   Diesels                                                   control improvements of 1980/81.

•Continuous reduction in overall emissions due to improvements in control
emission technology
•Steeper drop after 1987 because by then average vehicle age (7-8 years)6
suggests that the average car was purchased after the 1980/81 improvements.
• Leveling off after 1996 in LDGV&MC due to aging of fleet prior to replacement
with MY 1994 and later vehicles and continued increase in vehicle use.
•Decreased reduction in overall emissions after 1996 also due to the increased
relative emissions of LDGT.
                                             NOx Emissions
                        NO Emission


14,000

12,000

10,000                                                             •     Overall emissions trends determined
 8,000                                                                   by LDGV&MC and Diesels
 6,000

 4,000
                                                                   •     Reduction after 1987 in overall
 2,000
                                                                         emissions is lessened by increase in
    0
                                                                         emissions from diesel vehicles
    1960       1970       1980        1990    2000       2010

     HIGHWAY VEHICLES (Tier 1 - 11)            Light-Duty Gas Vehicles & Motorcycles
     Light-Duty Gas Trucks                     Heavy-Duty Gas Vehicles
     Diesels



•Overall emissions decrease because of increased emission control
technology in LDGV&MC.
•Emissions from LDGV&MC level off after 1998 due to increased use and
failure of MY 1994 improvements to have a significant impact yet.
•Rise in Diesel emissions due to increased use and lack of emission
technology for vehicles. Decrease after 1998 due to stricter MY 1991
emissions standards for truck and buses.
                                             VOC Emissions
                       VOC Emission


18,000                                                      •    Overall emissions trends
16,000                                                           determined by LDGV&MC
14,000
12,000                                                      •    Lower emissions for HDGV,
10,000                                                           LDGT, and Diesels because of
 8,000                                                           less use, as shown in “miles
 6,000
                                                                 driven”.
 4,000
 2,000
                                                            •             The effect of the increase in LDGT
    0
    1960       1970       1980        1990    2000        2010
                                                                          use is minimized because the
                                                                          increase comes a few years after
     HIGHWAY VEHICLES (Tier 1 - 11)
     Light-Duty Gas Trucks
                                                                          the emissions control
                                               Light-Duty Gas Vehicles & Motorcycles
                                               Heavy-Duty Gas Vehicles
     Diesels                                                              improvements of 1980/81.

•Continuous reduction in overall emissions due to improvements in control
emission technology.
•Steeper drop after 1987 because by then average vehicle age (7-8 years)6
suggests that the average car was purchased after the 1980/81 improvements.

•Leveling off in 1997 and 1998 in LDGV&MC due to aging of fleet prior to
replacement with MY 1994 and later vehicles and continued increase in vehicle
use.
                                                     SO2 Emissions
                         SO2 Emission

600                                                                    •   Overall emissions trends
500                                                                        determined by Diesels
400

300                                                                    •   Increased relative contribution of
200                                                                        LDGT corresponding to increase
100                                                                        in use of LDGT.
 0
 1965   1970   1975    1980    1985     1990   1995      2000   2005
                   HIGHWAY VEHICLES (Tier 1 - 11)
                   Light-Duty Gas Vehicles & Motorcycles
                   Light-Duty Gas Trucks
                   Heavy-Duty Gas Vehicles
                   Diesels



 •Increase in diesel emissions until 1990 because of increased use and little
 improvement in emission control technology.
 •Drop after 1990 corresponds to desulphurization of diesel fuel.
 •Level off after 1996 due to increased relative contribution of LDGT and
 LDGV&MC.
 •Little change in LDGV&MC over time since this emission source is minor and
 thus has yet to be dealt with for LDGV&MC.
                                                PM-10 Emissions
                      PM-10 Emissions
                                                                       •   Overall emissions trends
 600                                                                       determined by LDGV&MC and
 500                                                                       Diesels
 400

 300
                                                                       •   The effect of the increase in LDGT
 200
                                                                           use is minimized because the
 100
                                                                           increase comes a few years after
  0
                                                                           the emissions control
  1965   1970   1975    1980    1985     1990
                 HIGHWAY VEHICLES (Tier 1 - 11)  1995
                 Light-Duty Gas Vehicles & Motorcycles
                                                         2000   2005
                                                                           improvements of 1980/81.
                 Light-Duty Gas Trucks
                 Heavy-Duty Gas Vehicles
                 Diesels




•Decrease in LDGV&MC corresponds to initial improvements in emission control
technology.
•Increase in diesel emissions until 1990 because of increased use and little
improvement in emission control technology.
•Drop after 1990 corresponds to desulphurization of diesel fuel.
                                                            Emission Factors (g/gal)
                                             NOx Emisson Factor (g/gal)                                                                             VOC Emisson Factor (g/gal)


                         250                                                                                                   500
                                                                                                                               450
                         200                                                                                                   400
Emisson Factor (g/gal)




                                                                                                      Emisson Factor (g/gal)
                                                                                                                               350
                         150                                                                                                   300
                                                                                                                               250
                         100                                                                                                   200
                                                                                                                               150
                         50                                                                                                    100
                                                                                                                                50
                          0                                                                                                      0
                          1960          1970         1980     1990         2000          2010                                    1960         1970          1980       1990         2000          2010
                         HIGHWAY VEHICLES (Tier 1 - 11)       Light-Duty Gas Vehicles & Motorcycles                            HIGHWAY VEHICLES (Tier 1 - 11)         Light-Duty Gas Vehicles & Motorcycles
                         Light-Duty Gas Trucks                Heavy-Duty Gas Vehicles                                          Light-Duty Gas Trucks                  Heavy-Duty Gas Vehicles
                         Diesels                                                                                               Diesels




•Decrease in Diesel NOx emission factor after 1998 corresponds to decrease
in overall level of Diesel NOx emissions.
• Almost continuous decrease in emissions factors for all three gasoline
categories shows that emission reduction technology is working.
                                                                   Emissions Factor (g/mile)
                                                    NOx Emission Factor (g/mile)                                                                                         VOC Emission Factor (g/mile)

                           35                                                                                                                   80

                           30                                                                                                                   70
Emission Factor (g/mile)




                                                                                                                     Emission Factor (g/mile)
                           25                                                                                                                   60

                                                                                                                                                50
                           20
                                                                                                                                                40
                           15
                                                                                                                                                30
                           10
                                                                                                                                                20
                           5                                                                                                                    10

                           0                                                                                                                    0
                           1965       1970      1975     1980     1985      1990      1995       2000         2005                              1965       1970      1975     1980     1985      1990      1995       2000         2005

                                HIGHWAY VEHICLES (Tier 1 - 11)        Light-Duty Gas Vehicles & Motorcycles                                          HIGHWAY VEHICLES (Tier 1 - 11)        Light-Duty Gas Vehicles & Motorcycles
                                Light-Duty Gas Trucks                 Heavy-Duty Gas Vehicles                                                        Light-Duty Gas Trucks                 Heavy-Duty Gas Vehicles
                                Diesels                                                                                                              Diesels




                            •2002 levels (LDGV&MC - 1.19 g/m NOx, 1.37 g/m VOC) are still
                            significantly greater than 1996 emission standards (.41 NOx g/m and .25
                            g/m VOC)11.
                            •Thus, emissions can be greatly reduced by replacing older cars with
                            newer cars.
                    Emissions Summary

• The trends are a result of the competition between the effectiveness
  of the emission control technology in the national vehicle fleet and
  vehicle use.

• The improvements in emission control technology are effective
  enough to overcome the increase in vehicle usage.

• NOx emissions can be significantly reduced by improving Diesel
  NOx emission technology since NOx emission factors for Diesel
  vehicles are 7 times that emission factor for all vehicles and Diesel
  NOx emissions are greater than the other three vehicle categories.
                                   References
1.   United States. Office of Highway Policy Information. Highway Statistics Summary to 1995 (Historical
     Summary to 1995): Table VM-201a. April 1997. http://www.fhwa.dot.gov/ohim/summary95/vm201a.pdf
     23 March 2005.

2.   United States. Environmental Protection Agency. 1970 - 2002 Average annual emissions, all criteria
     pollutants. January 2005. ttp://www.epa.gov/ttn/chief/trends/trends02/trendsreportallpollutants010505.xls
     22 March 2005.

3.   Tooly, Rebecca Lee. Procedures Document For National Emission Inventory Criteria Air Pollutants
     1985-1999. United States Office of Air Quality. Environmental Protection Planning and Standards
     Agency. Research Triangle Park. NC March 2001.
     http://www.epa.gov/ttn/chief/trends/procedures/neiproc_99.pdf 22 March 2005.

4.   United States. Environmental Protection Agency. What are Mobile Sources?
     http://www.epa.gov/otaq/invntory/overview/examples.htm#onr 31 March 2005.

5.   Energy Futures, Inc. U.S. VEHICLE FUEL ECONOMY AT 20 YEAR LOW. http://www.energy-
     futures.com/samples/301cfr/g2.htm. 19 April 2005.

6.   Dill, Jennifer. Transportation Research Board. “Older Vehicles and Air Pollution: Insights from the 1995
     NPTS.” http://gulliver.trb.org/publications/circulars/ec026/23_dill.pdf. 17 April 2005.

7.   United States. Environmental Protection Agency. Mobile Source Emissions - Past, Present, and Future:
     Milestones. http://www.epa.gov/otaq/invntory/overview/solutions/milestones.htm. 13 April 2005.
8.    United States. Environmental Protection Agency. Automobile Emission: An Overview.
      http://www.epa.gov/otaq/consumer/05-autos.pdf. 17 April 2005.

9.    United States. Environmental Protection Agency. National Air Pollutant Emission Trends: 1900-
      1998. March 2000. http://www.epa.gov/ttn/chief/trends/trends98/chapter3.pdf. 17 April 2005.

10.   United States. Environmental Protection Agency. Diesel Exhaust in the United States. September
      2002. http://www.epa.gov/otaq/retrofit/documents/f02048.pdf 24 April 2005.

11.   United States. Environmental Protection Agency. Motor Vehicles and the 1990 Clean Air Act.
      http://www.epa.gov/otaq/consumer/11-vehs.pdf. 17 April 2005.

12.   United States. Environmental Protection Agency. EPA National News. “CLEANER CARS AND
      CLEANER FUELS FOR THE 21ST CENTURY.” 21 Dec. 1999.
      http://yosemite1.epa.gov/opa/admpress.nsf/b1ab9f485b098972852562e7004dc686/0b8d5154
      df6d30a18525684e0077437d?OpenDocument. 20 April 2005.

13.   United States. Environmental Protection Agency. Environmental News. “EPA DRAMATICALLY
      REDUCES POLLUTION FROM HEAVY-DUTYTRUCKS AND BUSES; CUTS SULFUR
      LEVELS IN DIESEL FUEL”. 21 Dec. 2000. http://www.epa.gov/otaq/regs/hd2007/frm/r-
      196.pdf 20 April 2005.

				
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