The Influence of Weight

1
The Influence of Weight

• Average model weight of light-duty gas vehicles
  and trucks
• Freight-ton miles per heavy-duty diesel truck

2
Source for Weight Data

• Data comes from Appendix H-1 of the EPA report
  (Ref.1.a)
• Conversion from cars, vans, SUVs, and pickup
  trucks to the light-duty gas vehicles and
  trucks
• Weight of Light-duty gas vehicles data for
  passenger cars only
• Weight of Light-duty gas trucks data for vans,
  SUVs, and pickup trucks only

• Weight data based on inertia weight class
  (ref1.b)
• Curb weight 300lb for vehicles up to and
  including 3000 lb
• (measured at 250 lb increments)
• Curb weight 500 lb for heavier than 3000 lb
  (measured at 500 lb increments)
• Average weight based on fraction of number of
  cars sold (Ni) for a weight class (Wi) out of the
  total number sold that year (NT)
• ?i1(NiWi)/?NT

Ref. 1.a 1.b
3
Analyzing Weight Trends

• 4 main parts to
• Light-duty Gas Weight
• Vehicles and trucks weighed the same in 1975
• Vehicles weighed less than trucks after 1975
• Both vehicles and trucks dropped their respective
  weights in 1980s
• Both vehicles and trucks increased their
  respective weights from the 1990s to current

Fig. 1 Weight data collected from the EPA Ref.
1.a.
4
Difference between light-duty gas vehicles and
trucks

• Vehicles and Trucks weighed the same in 1975
• Initially, light-duty gas vehicles were as heavy
  as trucks because of no standards for safety or
  emissions yet
• 2. Average weight of vehicles lighter than trucks
  after 1975
• Reasons for classification of light-duty gas
  truck
• (as not a light-duty gas vehicle)
• Mainly for commercial and agricultural work
• Few of them
• Significant because regulated less strictly
  under
• Energy Policy and Conservation Act for fuel
  economy
• Clean Air Act for emissions standards

Ref. 2
5
Weight Increase and Decrease

• Influence on weight decrease (1975-late 1980s)
• CAFÉ
• Govt. policy to increase fuel efficiency in
  1975(Ref. 3)
• FMVSS
• no safety changes from 1974 -1986 (Ref. 5)
• Influence on weight increase (late 1980s 2004)
• FMVSS
• Increase in weight of safety equipment (Ref. 5)
• Technology
• Used to increase weight and acceleration (Ref. 4)

6
CAFÉ Corporate Average Fuel Economy
Weight change in cars has little effect on
overall fuel efficiency

• Fuel economy from technology,
• not small cars
• 14 MPG in 1974 to 28.2 MPG in 1994
• 12.4 MPG or 87 results from technological
  improvements to passenger cars
• 1.6 MPG or 11.5 from weight loss
• 0.2 MPG or 1.4 from consumers buying smaller
  cars

• Due to Energy Policy and Conservation Act (EPCA)

Ref. 3
7
FMVSSFederal Motor Vehicle Safety Standards

• Federal Motor Vehicle Safety Standards (FMVSS)
• Reverse engineering to find out how much weight
  was going towards safety
• Safety includes avoiding crashes, fires, and
  other hazards, and regulating crashes.
• Weight in passenger cars changed little from
  1974-1986 because no new FMVSS changes
• Many safety technologies in cars later than in
  light trucks

Ref. 5
8
Technology Improvement Weight Gain

• Technology goes to increase weight and
  acceleration, not fuel economy
• Weight increased 21
• Horsepower increased 79

Ref. 4
If the 2000 model year light vehicle had the same
performance and weight as the 1981 model year,
there would have been a 25 higher fuel
efficiency Engineering improvements go to fuel
injection systems, engines with more valves, etc.
Ref. 3
9
Ton-mpg

• Ton-MPG is the miles per gallon times the weight
  in tons
• Tells ability to move weight
• Also tells about the power train and drive-line
  efficiency

Ref. 1.a.

• Even though weight has increased in cars, the
  miles per gallon has also improved.
• This signifies that weight alone does not
  indicate the fuel efficiency of a vehicle

10
Source of Freight-Ton Mile Data

• Data for ton-miles from two different sources
• 1970-1980 Eno Transportation
• 1990-2002 BTS (Bureau of Transportation
  Statistics)
• Measurements taken in 1970, 1980, 1990, and
  1994-2002
• The years in-between two known values and so were
  interpolated.
• Only intercity travel, not all travel over the
  entire USA
• Ton-miles in Millions of Miles
• Careful documentation of freight did not begin
  until the Commodity Flow Survey in 1993

Ref. 6, 7
11
Freight-Ton Miles

• Amount of freight being transported has
  increased every year
• Because the data is interpolated and from the
  intercity travel only, this graph does not
  accurately depict all freight travel in every
  year. However, the graph still reveals that the
  trend of freight-ton miles over time increased.

Ref. 6 7
12
Commodity Flow Survey
Change in fuel economy not due to weight of
heavy-duty diesels from 1990-2000

• Freight energy efficiency decline 6 by 2000
• a result of a slow 2 annual growth rate in
  ton-miles
• rapid annual growth rate of 2.5 in freight
  energy consumption
• There was no increase in ton-miles per vehicle
  mile from 1990 -2000

Ref. 8
The average weight per truck did not increase
much and yet the fuel efficiency went down. This
suggests that the weight carried by the truck is
not the reason for the change in fuel efficiency
from 1990-2000
Ref. 9
13
Conclusions on Weight

• Weight affects fuel economy
• However, the effect of weight changes on fuel
  economy was small compared to technology changes
  for light-duty gas vehicles and trucks.
• More freight is being circulated via trucks in
  2002 compared to 1975, but the weight per truck
  is remaining constant.

14
References

• 1. "Light-Duty Automotive Technology and Fuel
  Economy Trends 1975 Through 2004"
  (EPA420-R-04-001, April 2004)   840 K PDF, 98
  pages. http//www.epa.gov/otaq/fetrends.htm
• 1.a. APPENDIX H - Data Stratified by Weight Class
  121 K PDF (47 pages)
• 1.b. APPENDIX A - Database Details and
  Calculation Methods151 K PDF (15 pages)
• 2. Sport Utlility Vehicles, Mini-Vans and Light
  Trucks An Overview of Fuel Economy and Emissions
  Standards (CRS Report for Congress RS20298,
  January 2001) by Brent Yacobucci.
  lthttp//www.ncseonline.org/NLE/CRSreports/Air/air-
  32.cfm?CFID14609448CFTOKEN91022181Back3gt
• 3. STATEMENT OF CLARENCE M. DITLOW DIRECTOR,
  CENTER FOR AUTO SAFETY Before the SUBCOMMITTEE on
  ENERGY AND POWER HOUSE COMMITTEE on COMMERCE
  Washington DC July 24, 1995 lthttp//www.autosafety
  .org/article.php?did812scid77gt
• 4. EPA Access EPA report number EPA420-S-00-003,
  web www.epa.gov
• 5. Cost and Weight Added by the Federal Motor
  Vehicle Safety Standards for Model Years
  1968-2001 in Passenger Cars and Light Trucks by
  Marcia J. Tarbet (NHTSA Report Number DOT HS 809
  834,December 2004) lthttp//www.nhtsa.dot.gov/cars
  /rules/regrev/evaluate/809834.htmlgt

15
References

• 6. Eno Transportation Foundation, Inc.,
  Transportation in America, 2000 (Washington, DC
  2001), p. 12. lthttp//www.bts.gov/publications/nat
  ional_transportation_statistics/2004/html/table_tr
  uck_profile.htmlgt
• 7. U.S. Department of Transportation, Bureau of
  Transportation Statistics, special tabulation,
  Mar. 11, 2005. http//www.bts.gov/publications/nat
  ional_transportation_statistics/2004/html/table_tr
  uck_profile.html
• 8. Source Department of Transportation, Bureau
  of Transportation Statistics, National
  Transportation Statistics 2002, tables 1-44, 4-6.
  
• 9. Transportation Energy Efficiency Trends in
  the 1990s Department of Transportation, Bureau
  of Transportation Statistics, National
  Transportation Statistics 2002
  lthttp//www.bts.gov/publications/issue_briefs/numb
  er_02/html/transportation_energy_efficiency_trends
  _in_the_1990s.htmlgt