Carbon Footprint of the U.S. Population: Causes and Spatial-Temporal Pattern

1. Carbon Footprint of the U.S. Population: Causes and Spatial-Temporal Pattern VMT and PMT Class Project ME/ENV 449, 2007 Grace D. W. Johnson Instructor: R. Husar

2. Introduction to Causality Factor – VMT and PMT • Two of the statistical criteria used: • Vehicle-Miles Traveled (VMT) – Total miles traveled by vehicles by type of vehicle • Statistical data from odometer readings; accumulated by states; totaled nationally • Passenger-Miles Traveled (PMT) – Total miles traveled by passengers (i.e., occupants) of vehicles by vehicle type • Calculated by multiplying VMT by occupancy per type of vehicle

3. Notes of Interest: • From 1960 to 1969 Other 2-Axle 4-Tire Vehicles are listed with Single Trucks 2-Axle 6-Tire-or-more. • From 1960 to 1969 Motorcycles are listed with Passenger Cars. • Beginning in 1970 both Other 2-Axle 4-Tire Vehicles and Motorcycles are listed separately. • In 1997 FHWA reassigned minivans and SUVs from Passenger Cars to Other 2-Axle 4-Tire Vehicles.

4. Trends of VMT and PMT, 1960 - 2003 • VMT and PMT Totals Normalized to 1990 show consistently increasing growth rate. • VMT and PMT Totals for Air, Car, Heavy Truck, Bus, Rail, and Other reflect the same growth rates with PMT values a multiple of VMT values.

5. VMT and PMT for Air shows a continuous increase in growth but is low compared to data for Passenger Cars. • VMT and PMT for Car shows greatest values at ~2.75 MMiles VMT and ~4.5MMiles PMT with Passenger Cars leading all.

6. VMT for Heavy Truck from 1970 to 2003 shows Truck Combinations to be almost twice the miles as Single Trucks. • VMT for Bus shows erratic growth/decline with an overall increase. PMT for Bus has significant increase due to increase in number of buses registered.

7. VMT and PMT for Rail shows a slump in growth with recovery in 1990 and continuous increase since. Heavy Rail has the most miles for both VMT and PMT.

8. Parameters That Influence Vehicle and Passenger Miles • More people, More cars, More miles driven • As Car VMT increases, Car PMT doubles • As Car PMT increases, Car PMT per Person (per capita) increases • Car PMT per Person is the causality factor!

9. What Influences VMT and PMT? • Trip Purpose • Number of vehicles owned by a household • Type of vehicle • Age and fuel efficiency of vehicle • Household composition • Tourism, cross-country highways, and US-foreign borders • Personal reasons

10. Trip Purpose: • Can be Daily/Local (less than 50 miles) • Family and Personal Business Trips – window shopping or purchase of goods • School/Church – to school, college or university class, or to attend religious activity • Social and recreational – vacation, visit to family or friends, participating in sports, going to movies, or other entertainment • Work – to and from one’s place of work • Work-related – trips to meetings, conferences, or visiting clients

11. The number of family/personal business and social/recreational trips exceed even the number of work and work-related trips.

12. Trip Purpose: • Can be Long Distance (≥ 50 miles) • Business – trips for meetings, conferences, visiting clients, or any other purpose except commute • Commute – to and from work only • Pleasure – vacations, sightseeing excursions, rest & relaxation, visiting family or friends, and family or outdoor recreation • Personal or Family Business – medical visits, shopping, weddings, funerals, etc.

13. The number of pleasure trips is more than three times the number of trips for any other purpose. Note that 12.7% of all long distance trips are for commuting to work.

14. Long distance mean trip length has decreased by 29% from 1977 to 2001, as the number of annual person-trips have increased 402%. The percentage of long distance PMT versus total PMT has almost doubled in this same time period. The increased number of long distance trips has added up to 3.5 times the PMT for long distance as in 1977.

15. Number of vehicles owned by a household: • Higher income enables more people to own personal vehicles, cutting down on occupancy, increasing VMT, and decreasing PMT. • Type of Vehicle: • The more people seated in a vehicle, the more it is driven as social usage increases. • Minivans are driven more than sedans, and minivan and SUV purchases are on the rise. • Age of Vehicle: • Newer vehicles are driven more than older ones due to greater fuel efficiency and reliability.

16. Household composition: • Households with teenagers and higher incomes drive the most miles. • Households whose children have left home drive the least miles. • Household with teenagers drive more than households with young children. • Tourism, cross-country highways, and US-foreign borders: • Impact per capita fuel consumption and give an unrealistic valuation when cross-check with VMT of residents (example: Wyoming)

17. Vehicle-Miles Traveled on Highways, 1975 and 1998 Wyoming, one of the lowest in population, is the nation’s largest in VMT, while New York has one of the lowest VMT!

18. Personal Reasons: • Increased personal income prompts more cars and more travel • Travel for its own sake; can lead to unnecessary and excess driving • Driving as a free-time activity • Residing in the suburbs, far from work in urban area or in another suburb • Reside in sprawling urban area • Public transportation not an option • Drive to shop • Working more frequently or postponing retirement

19. Suggestions To Change Miles Per Vehicle • Use mass transit whenever possible • Increase vehicle occupancy • Purchase vehicles that seat more people • Limit the number vehicles owned • Limit “excess” driving • Reside closer to work