1. Energy III:
Methods for Measuring Transport Energy Use
Class #5
I. How to Measure and Evaluate Energy Use?
II. Framework for Analyzing Energy Use
III. Factors Affecting Operating Energy
IV. How to Lie With Statistics

2. I. How to measure and evaluate energy
use?
Answer: Energy input per unit of output
A. What units?
Output units? VMT, VKT, pass-miles (PMT), seat-miles, trip, ton-miles of cargo, ton-
mile of capacity, etc.
Energy inputs: Btu, joules, kilocalories, kilowatts, gallons, barrels,etc
Btu = energy to raise temp of 1 lb of water 1°F
1 Btu = 1055 joules; 1015 Btu = 1 quad
120,000 BTU = 1 gallon gasoline (10% more btu/gallon for diesel)
1 bbl = 42 gallon
B. Key Measure: Energy-intensiveness -- energy used per unit of
output
But how broadly does one measure amount of energy used? Typical
measurement of energy used is only energy used for propulsion (easy to compute
and understand, based on easily available aggregate data, convenient for
comparing vehicles or modes).
Is this a useful or accurate method?

3. Modes
Basic energy components Measures of energy use
Energy
• Propulsion energy per vehicle-mile intensive-
• Average number of occupants ness Line-
haul
• Station and maintenance energy energy
Modal
• Construction energy energy
• Vehicle manufacturing energy
• Mode of access
• Fraction of trip devoted to access
• Circuity
Source: Congressional Budget Office, Committee on Environment and Public Works (1977)

4. II. Framework for Analyzing Energy Use
Sample Breakdowns
Air
RR Cargo BART Energy Component Measures of Energy Use
39 91 40 Propulsion energy Operating energy
(per unit of output (ie, energy Line
eg, ton-mile) intensiveness) haul
energy
10 3 16 Terminal & maintenance energy
12 4 44 Guideway construction Modal
5 1 ? Vehicle manufacturing energy Energy
? ? - Energy Used in Access
34 5 ? Circuity (including empty backhauls)
100% 100% 100%
Terminology:
Direct energy = propulsion energy
Indirect energy = construction, maintenance, & operation of
guideways and terminals, and construction of vehicles

5. III. Factors affecting operating energy
 Gradient (600% difference between –7% and +7% grade)
 Curvature of road
 # stops/unit distance (2 stops/mile => 56% more fuel than at steady 40
mph)
 Load factor (trucks empty 8% of time, rail 40%)
 Pavement condition: good pavement provides 40% (1 vs 1.7) better fuel
economy than gravel road and 33% better than broken pavements)
 Speed: at 80mph, vehicles consume ~50% more energy than at 50 mph
 Temp: 15% more fuel consumed at –20 degrees C than at +20 degrees C
 Trip length (hot/cold start): ~4 times more energy used (per km) for very
short trip vs longer trip of 30 km.
 Vehicle characteristics: aerodynamics (air friction), vehicle weight, tire
type (rolling friction), engine, transmission friction, regenerative
braking

6. IV. How to Lie With Statistics

7. Flaw #1: What about upstream energy use?
Feedstock recovery Fuel recovery Vehicle operation
Analysis on previous slide based only on tank-to-wheels
efficiency (ignores upstream well-to-tank energy use)!
Analysis of well-to-wheels energy use (and emissions) is generally referred
to as lifecycle analysis (LCA)
When are upstream emissions more important?
The GREET Model (Greenhouse Gases, Regulated Emissions, and Energy Use in Transportation) is
extremely useful for analyzing energy use and GHGs for lifecycle analysis and can be found at:
http://www.transportation.anl.gov/software/GREET/index.html

8. Petroleum Fuel Pathway
Battery EV Pathway

9. Greenhouse Gas Emissions per Km, Relative to Gasoline-
Powered ICE, Full Energy Cycle
Fuel/Feedstock % Change
Fuel Cells, Hydrogen with Solar Power -90 to –85
Ethanol from Wood -90 to –40
BEVs, Natural Gas Plants -60 to –25
Hybrid EV (Prius) -40 to -30
Diesel -25 to -15
CNG from NG -20 to 0
Methanol from NG -10 to +8
BEVs, current U.S. power mix -20 to 0
Gasoline -
BEVs, new coal plant 0 to +10
Actual impacts could vary considerably. These estimates reflect a large number of
assumptions and should be treated as illustrative.

10. Flaw #2: Energy intensiveness measures are average rates that
ignore or simplify differences in:
1. Vehicle characteristics (size, engine, aerodynamics, etc)
2. Vehicle loads (car with 1 pass vs 5 pass)
3. Operating conditions (speed, pavement, temp, weather)
4. Energy required for construction of vehicles, guideways,
terminals, and for maintenance of facilities
5. Circuity
6. Access energy

11. Is Transit More Energy Efficient Than Cars?
4500
4000
3500
Btu/passenger-mile
3000 Cars
2500 Light Trucks
Light Trucks
Rail Transit
2000 Bus
1500 Rail Transit
Cars
Bus
These are averages for US.
1000 Actual intensities vary
500 dramatically across time of
day, routes, and regions
0 (and by trip purpose for
cars).
Source: US DOE and ORNL, Transportation Energy Data Book, Edition 26, 2007

12. More EI Estimates for Vehicles (US)
Energy Intensity of U.S. Passenger Travel, 2007
5000
Btu/Passenger Mile
4500
4000
3500
3000
2500
2000
1500
1000
500
0
source: Davis, et al, 2009

13. CO2e Emissions by Mode Per Passenger Mile
NATIONAL AVERAGE* Energy Intensities Load CO2e
Factor
(Btu or (Estimated
(Btu or kWhr kWhr per Pounds CO2e
per vehicle passenger Persons Per Per Passenger
mile) mile) Vehicle Mile)
Cars 5,489 3,496 1.57 0.58
Personal Trucks 7,447 4,329 1.72 0.71
Motorcycles 2,500 2,272 1.1 0.37
Vanpool 8,226 1,294 6.4 0.21
Transit Bus 38,275 4,318 8.7 0.71
Electric Trolley Bus** 5.18 0.39 13.4 0.52
Intercity Rail (Amtrak)*** 51,948 2,760 17.9 0.39
Light and Heavy Rail Transit*** 70,170 2,750 22.4 0.39
Commuter Rail*** 91,525 2,569 32.9 0.36
Walking or Biking 0 0 1.0 0.00
REGIONAL EXAMPLE Energy Intensities Load CO2e

14. Flaw #3: Other associated impacts ignored. Need to determine
what is real goal.
How important is energy use analysis?
• Why measure only petroleum?
• More important than carbon emissions?
• What about other benefits and costs?
 Other transit benefits??