Fuel efficiency in transportation

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Summary
Mode Efficiency
per passenger
Biking 653 mpg
TGV train 506 mpg
Colorado Railcar 328 mpg
Walking 235 mpg
Bus 231 mpg
Airplane 78 mpg
Steamship 18 mpg

This page describes fuel efficiency in means transportation.

  • Humans (see Human-powered transport):
    • walking or running one kilometre requires approximately 70 kcal or 330 kJ of food energy [1]. This equates to about 1 L/100 km or 235 mpg in gasoline energy terms.
    • cycling requires about 120 kJ/km[1] This equates to about 0.36 L/100 km or 653 mpg of gasoline
  • Airplanes: passenger airplanes averaged 4.8 L/100 km per passenger (1.4 MJ/passenger-km) (49 passenger-miles per gallon) in 1998. Efficiencies around 3 L/100 km per passenger are reached by some carriers. [2]. Note that on average 20% of seats are left unoccupied. Aircraft efficiencies are improving: Between 1960 and 2000 there has been a 70% overall fuel efficiency gain. [3]
  • Ships: the RMS Queen Elizabeth 2 gets 49.5 feet per gallon, or 0.009375 mpg, or 18 passenger-miles per gallon (25,000 L/100 km or 13 L/100 km per passenger (3.8 MJ/passenger-km)).[citation needed] 40% of the power produced by the ship engines is used for propulsion, the rest being used to generate electricity for heating, lighting, and other passenger comforts.[citation needed]
  • Trains:
    • Freight: the AAR claims an energy efficiency of over 400 short ton-miles per gallon of diesel fuel in 2004[4] (0.588 L/100 km per tonne or 235 J/(km·kg))
    • Passengers: the East Japan Railway Company claims for 2004 an energy intensity of 20.6 MJ/car-km, or about 0.35 MJ/passenger-km[5]
    • a 1997 EC study[6] on page 74 claims 18.00 kWh/train-km for the TGV Duplex assuming 3 intermediate stops between Paris and Lyon. This equates to 64.80 MJ/train-km. With 80% of the 545 seats filled on average [7] this is 0.15 MJ/passenger-km, or 506 passenger-mpg in gasoline energy equivalent.
    • Actual train consumption depends on gradients, maximum speeds and stopping patterns. Data was produced for the European MEET project (Methodologies for Estimating Air Pollutant Emissions) and illustrates the different consumption patterns over several track sections. The results show the consumption for a German ICE High speed train varied between around 19Kwh/km to 33 Kwh/km. The data also reflects the weight of the train per passenger. For example, the TGV double-deck ‘Duplex’ trains use lightweight materials in order to keep axle loads down and reduce damage to track, this saves considerable energy. [8]
    • a Siemens study of Combino light rail vehicles in service in Basel, Switzerland over 56 days showed net consumption of 1.53 kWh/vehicle-km, or 5.51 MJ/vehicle-km. Average passenger load was estimated to be 65 people, resulting in average energy efficiency of 0.085 MJ/passenger-km. The Combino in this configuration can carry as many as 180 with standees. 41.6% of the total energy consumed was recovered through regenerative braking.[9]
    • a trial of a Colorado Railcar double-deck DMU hauling two Bombardier Bi-level coaches found fuel consumption to be 128 US gallons for 144 miles, or 1.125 mpg. The DMU has 92 seats, the coaches typically have 162 seats, for a total of 416 seats. With all seats filled the efficiency would be 468 passenger-mpg, with 70% filled the efficiency would be 328 passenger-mpg. This latter figure translates to 0.27 MJ/passenger-km.[10]
    • Note that intercity rail in the U.S. reports 3.17 MJ/passenger-km which is several times higher than reported from Japan. Independent transportation researcher David Lawyer attributes this difference to the fact that the losses in electricity generation may not have been taken into account for Japan[11] and that Japanese trains have a larger number of passenger per car. [12]
    • Modern electric trains like the shinkansen use regenerative braking to return current into the catenary while they brake. This method results in significant energy savings, where-as diesel locomotives (in use on unelectrified railway networks) typically dispose of the energy generated by dynamic braking as heat into the ambient air.[citation needed]
    • This Swiss Railroad company SBB-CFF-FFS cites 0.082 kWh per passenger-km for traction, which is equivalent to 279 MPG [13]
    • AEA carried out a detailed study of road and rail for the United Kingdom Department for Transport. Final report
  • Buses:
    • the fleet of 244 1982 New Flyer 40 foot trolley buses in local service with BC Transit in Vancouver, BC, Canada in 1994/95 consumed 35454170 kWh for 12966285 vehicle-km, or 9.84 MJ/vehicle-km. Exact ridership on trolleybuses is not known, but with all 34 seats filled this would equate to 0.32 MJ/passenger-km. It is quite common to see standees on Vancouver trolleybuses. Note that this is a local transit service with many stops per km; part of the reason for the efficiency is the use of regenerative braking.
    • a diesel bus commuter service in Santa Barbara, CA, USA found average diesel bus efficiency of 6.0 mpg (using MCI 102DL3 buses). With all 55 seats filled this equates to 330 passenger-mpg, with 70% filled the efficiency would be 231 passenger-mpg, or 0.34 MJ/passenger-km.[14]
  • Rockets:
    • The NASA space shuttle consumes 1,000,000 kg of solid fuel and 2,000,000 litres of liquid fuel over 8.5 minutes to take the 100,000 kg vehicle (including the 25,000 kg payload) to an altitude of 111 km and an orbital velocity of 30,000 km/h. Due to orbital decay this could not be a one-way trip, however if one supposes it is one-way for the purpose of illustration, this would amount to about 3,300 GJ of energy, or about 100,000 L/100 km or 12 feet per gallon (0.0023 mpg) of gasoline. In reality the shuttle continues to use its velocity to maintain a gradually-decaying orbit (analogous to driving to the top of a very tall mountain and coasting back down a very gentle slope, thus adding many miles to the distance travelled). The space shuttle Atlantis flew approximately 4.9 million miles on the STS-115 mission and this greater distance means much higher fuel efficiency for that particular mission. It's worth noting that a rocket can, in theory, re-entry on any place on Earth, giving it a best-case "ground" distance of 20,000 km. This would amount to 500 L/100 km or about 0.5 mpg.

Electric motors are used to drive vehicles because they can be finely controlled, they deliver power efficiently and they are mechanically very simple. Electric motors often achieve 90% conversion efficiency over the full range of speeds and power output and can be precisely controlled. Electric motors can provide high torque while an EV is stopped, unlike internal combustion engines, and do not need gears to match power curves. This removes the need for gearboxes and torque converters. Electric motors also have the ability to convert movement energy back into electricity, through regenerative braking. This can be used to reduce the wear on brake systems and reduce the total energy requirement of a trip.

[edit] Transport comparison:

  • The UK DfT state the following figures for public transport in 2005 [15]:
UK Public transport
Transport mode Load factor (passengers per vehicle) Fuel consumption (Miles per gallon per passenger)
Buses (national) 9 98
Passenger rail (diesel) 90 182
Air short haul 100 40
Air long haul 300 66
  • The US Transportation Energy Data Book states the following figures for Passenger transportation in 2003 [16]:
US Passenger transportation
Transportation mode Load factor (passengers per vehicle) Fuel consumption (BTUs per passenger mile)
Cars 1.57 3,549
Personal Trucks 1.72 4,008
Motorcycles 1.22 2,049
Buses (Transit) 8.7 4,160
Air N/A 3,587
Rail (Intercity Amtrak) 17.2 2,935
Rail (Transit Light & Heavy) 21.7 3,228
Rail (Commuter) 33.4 2,571

Note: The actual MPG figure for each mode depends on the percentage of seats filled per vehicle, or load factor. Commuter rail and bus generally have lower load factors than air because of their 'walk on' nature, whereas long distance rail and airlines use yield management techniques which raise loads, typically 71% for TGV services in France and 80-90% for Airlines. The overall load factor on UK railways is 33% or 90 people per train [17]:

  • The US Transportation Energy book states the following figures for Freight transportation in 2003 [18]: [19]: [20]:
US Freight transportation
Transportation mode Fuel consumption (BTUs per ton mile)
Heavy Trucks 3,357
Class 1 Railroads 344
Air freight 9,600 (aprox)
Domestic Waterbourne 417
  • An independent compilation of real-world efficiency statistics, with references, can be found at strickland.ca/efficiency.html. The author welcomes further substantiated data references.
  • ECCM Study for rail, road and air journeys between main UK cities [3]

[edit] Footnotes

  1. ^ a b [1]
  2. ^ IATA - Fuel efficiency, IATA
  3. ^ National Aerospace Laboratory
  4. ^ Railroads: Building a Cleaner Environment, Association of American Railroads
  5. ^ Environmental Goals and Results, JR-East Sustainability Report 2005
  6. ^ Estimating Emmissions from Railway Traffic
  7. ^ European Environment Agency Occupancy Rates, page 3
  8. ^ Commission for integrated transport, Short haul air v High speed rail
  9. ^ Combino - Low Floor Light Rail Vehicles Tests, Trials and Tangible Results
  10. ^ Colorado Railcar: "DMU Performs Flawlessly on Tri-Rail Service Test"
  11. ^ Fuel Efficiency of Travel in the 20th Century, Appendix
  12. ^ Fuel Efficiency of Travel in the 20th Century
  13. ^ SBB Environmental Report 2002/2003
  14. ^ Demonstration of Caterpillar C-10 Duel-Fuel Engines in MCI 102DL3 Commuter Buses
  15. ^ Hansard, Commons Answers
  16. ^ Transportation Energy Data Book, 2006
  17. ^ [2] ATOC
  18. ^ Transportation Energy Data Book, 2006
  19. ^ US Environmental protection, 2006
  20. ^ EIA
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