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					 Class Project Report, May 2005
 ME/ChE 449 Sustainable Air Quality

      Highway Transportation:
Trends from 1970 to 2002 and Beyond


              Scott Kaminski

                Rudolf B. Husar
       Washington University, St. Louis, MO
                          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)
            Important Emission Improvements
•   1968 – Tailpipe emission standards first implemented for new cars to reduce VOC
    and CO emissions.1

•   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.2

•   1971 - New cars have to meet evaporative emission standards for the first time and
    charcoal canisters are introduced to collect VOC vapors.2,3

•   1972 - Exhaust gas recirculation valves are implemented to reduce NOx emissions.2
•   1975 – Most new cars have catalytic converters to reduce VOC and CO emissions.3
    Unleaded gasoline introduced (with a 13% market share) since lead inactivates the
    catalytic converters. Market share climbs to 50% in 1982 and 100% in 1996.4

•   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.2
•   1983 – Passenger Vehicles are first required to undergo testing for “malfunctioning
    emission control systems”.2
•   1990 – CAA Amendments passed including increasing testing requirements.1 Limit
    on diesel fuel sulfur content (to reduce SO2 and PM emissions) is set by EPA to take
    effect in 1993.2
•   1991 – Lower tailpipe standards set for VOC and NOx emissions to be phased in
    beginning in 1994.1 NOx and PM emissions standards for new trucks and buses cut
    in half.3
•   1992 – Limits for CO emissions at cold temperatures are set to be phased in
    beginning in 1994.1
•   1994 – The PM emissions standard for trucks and buses is cut by 60%.3
•   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).1 Standard for sulfur content in gasoline is reduced to take effect in 2005.4
•   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.5
                            CO Emissions

•Overall emission trends determined by LDGV&MC emission trends.
•Steeper drop after 1987 because by then average vehicle age (7.6 years)1
suggests that the average car was purchased after the 1980/81 improvements.
•Leveling off after 1996 in LDGV&MC due to aging of fleet (average vehicle age
8.5 years) prior to replacement with MY 1994 and later vehicles and continued
increase in vehicle use.
•The similarity in 2002 emissions per gallon (LDGT 4.2% better grams/gal
emissions factor than LDGV&MC) is deceiving because LDGV&MC have a
26.1% better MPG than LDGT and so LDGV&MC will produce less emissions
for the same trip.
                          NOx Emissions

•Overall emissions trends determined by LDGV&MC and Diesels.
•Rise in Diesel emissions due to increased use and nearly constant
emission factor.1 Decrease after 1998 due to stricter MY 1991 emissions
standards for truck and buses (average truck age 8.3 years).2
•NOx emissions can be significantly reduced by improving Diesel NOx
emission technology: Diesel NOx emission factor is 7 times that of the
overall NOx emission factor and absolute Diesel NOx emissions are greater
than the other three vehicle categories (46% of total).
                           VOC Emissions

•Overall emission trends determined by LDGV&MC emission trends.

•Lower absolute emissions for HDGV, LDGT, and Diesels because of less use, as
shown in miles driven. Higher relative absolute LDGT emissions as use
•Continuous decrease in emissions factors because of continual improvements in
emission technology and vehicle turnover.
•The greater reduction in VOC emission factors over NOx emissions factors (85.2
% to 77.1 % LDGV&MC) can be attributed to improvements in evaporation
emission technology as well as exhaust emission technology.1
                            SO2 Emissions

•Overall emissions trends determined by Diesels: Overall SO2 emissions minor
compared to NOx (26.8 times in 2002) and VOC emissions (16.5 times).
•Large emissions factor prevails over a lesser amount of Diesel vehicle use.
•Drop after 1990 in both absolute emissions and emissions factors corresponds
to desulphurization of diesel fuel.
•Little change in LDGV&MC over time since this emission source is minor and
has yet to be dealt with for LDGV&MC.1
                           PM-10 Emissions

•Overall emissions trends determined by LDGV&MC and Diesels.
•Incline of emission factor from 1980 – 1987 can be attributed to an aging vehicle
fleet (average truck age goes from 7.1 years to 8.0 years)1 and lack of significant
technological improvement or stringent emissions standards.2,3
•Drop after 1990 in both absolute emissions and emissions factors corresponds to
desulphurization of diesel fuel and, later on, to stricter emissions standards for MY
1991 trucks and buses.
                    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 decrease in emission factors for each pollutant shows that
  emission technology is working.

• The decrease in absolute emissions shows that emission
  technology is progressing faster than the increase in vehicle usage.

•   Difference between improvements in emissions factors and
    absolute emissions (ex. 85.2 % decrease to 73.1% decrease for
    overall VOC) is the increase in vehicle use .

• Full advantage of emission technology can only be achieved
  through halting upward trend in vehicle use.

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