Fuel Consumption

Data Consistency• “Number of vehicles”, “miles

driven”, and “fuel consumption” data given in six categories by the FHWA:1

– Passenger Cars– Buses– Motorcycles– Other 2-Axle, 4-Tire Vehicles– Single Unit Trucks– Combination Trucks

• “Emissions” data given in four categories by EPA:2

– Light Duty Gas Vehicles and Motorcycles (LDGV&MC)

– Light Duty Gas Trucks (LDGT)– Heavy Duty Gas Vehicles

(HDGV)– Diesels

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

•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”

Fuel Consumption

0

20000

40000

60000

80000

100000

120000

140000

160000

180000

1965 1970 1975 1980 1985 1990 1995 2000 2005

Total Light-Duty Gas Vehicles & MotorcyclesLight-Duty Gas Trucks Heavy-Duty Gas VehiclesDiesels

Miles Driven

0

500,000

1,000,000

1,500,000

2,000,000

2,500,000

3,000,000

1970

1972

1974

1976

1978

1980

1982

1984

1986

1988

1990

1992

1994

1996

1998

2000

2002

Total Light-Duty Gas Vehicles & Motorcycles

Light-Duty Gas Trucks Heavy-Duty Gas Vehicles

Diesels

MPG per Model Year5 Compared to NationalVehicle Fleet MPG

FUEL ECONOMY OF U.S. VEHICLES BY MODEL YEAR

FIGURE 1

SOURCE: EPA

Miles Per Gallon Trend

0

5

10

15

20

25

1965 1970 1975 1980 1985 1990 1995 2000 2005

MP

G

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

Light-Duty Gas Trucks Heavy-Duty Gas Vehicles

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 EmissionsCO Emission

0

20,000

40,000

60,000

80,000

100,000

120,000

140,000

160,000

180,000

1965 1970 1975 1980 1985 1990 1995 2000 2005

HIGHWAY VEHICLES (Tier 1 - 11)Light-Duty Gas Vehicles & MotorcyclesLight-Duty Gas TrucksHeavy-Duty Gas VehiclesDiesels

• Overall emission trends determined by LDGV&MC emission trends

• Lower emissions for HDGV, LDGT, and Diesels because of less use, as shown in “miles driven”.

• The effect of the increase in LDGT use is minimized because the increase comes a few years after the emissions 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 EmissionsNO Emission

0

2,000

4,000

6,000

8,000

10,000

12,000

14,000

1960 1970 1980 1990 2000 2010

HIGHWAY VEHICLES (Tier 1 - 11) Light-Duty Gas Vehicles & MotorcyclesLight-Duty Gas Trucks Heavy-Duty Gas VehiclesDiesels

• Overall emissions trends determined by LDGV&MC and Diesels

• Reduction after 1987 in overall emissions is lessened by increase in emissions from diesel vehicles

•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 EmissionsVOC Emission

0

2,000

4,000

6,000

8,000

10,000

12,000

14,000

16,000

18,000

1960 1970 1980 1990 2000 2010

HIGHWAY VEHICLES (Tier 1 - 11) Light-Duty Gas Vehicles & MotorcyclesLight-Duty Gas Trucks Heavy-Duty Gas VehiclesDiesels

• Overall emissions trends determined by LDGV&MC

• Lower emissions for HDGV, LDGT, and Diesels because of less use, as shown in “miles driven”.

• The effect of the increase in LDGT use is minimized because the increase comes a few years after the emissions 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 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

0

100

200

300

400

500

600

1965 1970 1975 1980 1985 1990 1995 2000 2005HIGHWAY VEHICLES (Tier 1 - 11)Light-Duty Gas Vehicles & MotorcyclesLight-Duty Gas TrucksHeavy-Duty Gas VehiclesDiesels

• Overall emissions trends determined by Diesels

• Increased relative contribution of LDGT corresponding to increase in use of LDGT.

•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

0

100

200

300

400

500

600

1965 1970 1975 1980 1985 1990 1995 2000 2005HIGHWAY VEHICLES (Tier 1 - 11)Light-Duty Gas Vehicles & MotorcyclesLight-Duty Gas TrucksHeavy-Duty Gas VehiclesDiesels

• Overall emissions trends determined by LDGV&MC and Diesels

• The effect of the increase in LDGT use is minimized because the increase comes a few years after the emissions control improvements of 1980/81.

•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)

•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.

VOC Emisson Factor (g/gal)

0

50

100

150

200

250

300

350

400

450

500

1960 1970 1980 1990 2000 2010

Em

isso

n F

acto

r (g

/gal

)

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

Light-Duty Gas Trucks Heavy-Duty Gas VehiclesDiesels

NOx Emisson Factor (g/gal)

0

50

100

150

200

250

1960 1970 1980 1990 2000 2010

Em

isso

n F

acto

r (g

/gal

)

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

Light-Duty Gas Trucks Heavy-Duty Gas Vehicles

Diesels

Emissions Factor (g/mile)

•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.

NOx Emission Factor (g/mile)

0

5

10

15

20

25

30

35

1965 1970 1975 1980 1985 1990 1995 2000 2005

Em

issi

on F

acto

r (g

/mile

)

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

Light-Duty Gas Trucks Heavy-Duty Gas Vehicles

Diesels

VOC Emission Factor (g/mile)

0

10

20

30

40

50

60

70

80

1965 1970 1975 1980 1985 1990 1995 2000 2005

Em

issi

on F

acto

r (g

/mile

)

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

Light-Duty Gas Trucks Heavy-Duty Gas Vehicles

Diesels

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.

References1. 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/b1ab9f485b098972852562e7004dc686/0b8d5154df6d30a18525684e0077437d?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.