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

Highway Transportation:

Trends from 1970 to 2002 and Beyond

By

Scott Kaminski

Instructor

Rudolf B. Husar

Washington University, St. Louis, MO

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)

Emissions

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 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

Th

ou

sa

nd

Sh

ort

To

n

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

•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.

CO Emission Factors (g/gal)

0

1000

2000

3000

4000

5000

6000

7000

1965 1970 1975 1980 1985 1990 1995 2000 2005

Em

issi

on

Fac

tors

(g

/gal

)

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

NOx EmissionsNO Emission

0

2,000

4,000

6,000

8,000

10,000

12,000

14,000

1965 1970 1975 1980 1985 1990 1995 2000 2005

Th

ou

san

d S

ho

rt T

on

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.

•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).

NOx Emisson Factor (g/gal)

0

50

100

150

200

250

1965 1970 1975 1980 1985 1990 1995 2000 2005

Em

isso

n F

acto

r (g

/gal

)

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

VOC EmissionsVOC Emisson Factor (g/gal)

0

50

100

150

200

250

300

350

400

450

500

1965 1970 1975 1980 1985 1990 1995 2000 2005

Em

isso

n F

acto

r (g

/gal

)

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

•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 increases.

•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

VOC Emission

0

2,000

4,000

6,000

8,000

10,000

12,000

14,000

16,000

18,000

1965 1970 1975 1980 1985 1990 1995 2000 2005

Th

ou

san

d S

ho

rt T

on

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

SO2 EmissionsSO2 Emission

0

100

200

300

400

500

600

1965 1970 1975 1980 1985 1990 1995 2000 2005

Th

ou

sa

nd

Sh

ort

To

n

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

•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

SO2 Emission Factor (g/gal)

0

2

4

6

8

10

12

14

16

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

PM-10 EmissionsPM10 Emission Factor (g/gal)

0

2

4

6

8

10

12

14

16

1965 1970 1975 1980 1985 1990 1995 2000 2005

Em

iss

ion

Fa

cto

r (g

/ga

l)

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.

•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.

PM-10 Emissions

0

100

200

300

400

500

600

1965 1970 1975 1980 1985 1990 1995 2000 2005

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

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.