Fuel efficiency in transportation - AbsoluteAstronomy.com

This page describes fuel efficiency
Fuel efficiency
Fuel efficiency is a form of thermal efficiency, meaning the efficiency of a process that converts chemical potential energy contained in a carrier fuel into kinetic energy or work. Overall fuel efficiency may vary per device, which in turn may vary per application, and this spectrum of variance is...

in means of transportation. For the environmental impact assessment
Environmental impact assessment
An environmental impact assessment is an assessment of the possible positive or negative impact that a proposed project may have on the environment, together consisting of the natural, social and economic aspects....

of a given product
Product (business)
In general, the product is defined as a "thing produced by labor or effort" or the "result of an act or a process", and stems from the verb produce, from the Latin prōdūce ' lead or bring forth'. Since 1575, the word "product" has referred to anything produced...

or service throughout its lifespan, see life cycle assessment
Life cycle assessment
A life-cycle assessment is a technique to assess environmental impacts associated with all the stages of a product's life from-cradle-to-grave A life-cycle assessment (LCA, also known as life-cycle analysis, ecobalance, and cradle-to-grave analysis) is a technique to assess environmental impacts...

.

The fuel efficiency in transportation ranges from some hundred kilojoule per kilometre for a bicycle to several megajoule for a helicopter.

Efficiency can be expressed in terms of consumption per unit distance per vehicle, consumption per unit distance per passenger or consumption per unit distance per unit mass of cargo

Cargo

Cargo is goods or produce transported, generally for commercial gain, by ship, aircraft, train, van or truck. In modern times, containers are used in most intermodal long-haul cargo transport.-Marine:...

transported.

Transportation modes

For freight transport, rail

Rail transport

Rail transport is a means of conveyance of passengers and goods by way of wheeled vehicles running on rail tracks. In contrast to road transport, where vehicles merely run on a prepared surface, rail vehicles are also directionally guided by the tracks they run on...

and ship transport

Ship transport

Ship transport is watercraft carrying people or goods . Sea transport has been the largest carrier of freight throughout recorded history. Although the importance of sea travel for passengers has decreased due to aviation, it is effective for short trips and pleasure cruises...

are generally much more efficient than trucking

Truck driver

A truck driver , is a person who earns a living as the driver of a truck, usually a semi truck, box truck, or dump truck.Truck drivers provide an essential service to...

, and air freight is much less efficient.)

Walking

A 140 lb (64 kg) person walking at 3 mi/h (~5 km/h) requires approximately 80 kcal (330 kJ) of food energy
Food energy
Food energy is the amount of energy obtained from food that is available through cellular respiration.Food energy is expressed in food calories or kilojoules...

per mile (~205 kJ/km).
Given that 1 gallon (~3.7854 liter) of gasoline contains about 114,000 BTU (120 MJ) of energy, this converts to roughly 360 MPG (0.65 l/100 km).
The latter figure, however, assumes a 100% conversion of the stored energy in gasoline to mechanical work. To use the example of an actual typical modern gasoline internal combustion engine
Internal combustion engine
The internal combustion engine is an engine in which the combustion of a fuel occurs with an oxidizer in a combustion chamber. In an internal combustion engine, the expansion of the high-temperature and high -pressure gases produced by combustion apply direct force to some component of the engine...

, in which roughly 20% of the energy of combustion does actual work (approximately 70% of the energy is lost as heat, and an additional 10% to parasitic losses and mechanical drag), the above figure converts to about 72 MPG (3.25 l/100km). Some motorcycles
Motorcycle
A motorcycle is a single-track, two-wheeled motor vehicle. Motorcycles vary considerably depending on the task for which they are designed, such as long distance travel, navigating congested urban traffic, cruising, sport and racing, or off-road conditions.Motorcycles are one of the most...

and a handful of very small cars are able to achieve such consumption rates in practice.

Bicycling

As a relatively light and slow vehicle, with low-friction tires, and an efficient chain-driven

Chain drive

Chain drive is a way of transmitting mechanical power from one place to another. It is often used to convey power to the wheels of a vehicle, particularly bicycles and motorcycles...

drivetrain

Powertrain

In a motor vehicle, the term powertrain or powerplant refers to the group of components that generate power and deliver it to the road surface, water, or air. This includes the engine, transmission, drive shafts, differentials, and the final drive...

, the bicycle

Bicycle

A bicycle, also known as a bike, pushbike or cycle, is a human-powered, pedal-driven, single-track vehicle, having two wheels attached to a frame, one behind the other. A person who rides a bicycle is called a cyclist, or bicyclist....

can be an efficient form of transport. A 140 lb (64 kg) cyclist riding at 16 km/h requires about half the energy per unit distance of walking: 43kcal

Calorie

The calorie is a pre-SI metric unit of energy. It was first defined by Nicolas Clément in 1824 as a unit of heat, entering French and English dictionaries between 1841 and 1867. In most fields its use is archaic, having been replaced by the SI unit of energy, the joule...

/mi or 3.1 kWh/100 km. This figure depends on the speed and mass of the rider: greater speeds give higher air drag and heavier riders also consume more energy per unit distance. This converts to about 732 MPG, or 146MPG assuming a 20% conversion rate.

A motorized bicycle

Motorized bicycle

A motorized bicycle, motorbike, cyclemotor, or vélomoteur is a bicycle with an attached motor and transmission used either to power the vehicle unassisted, or to assist with pedaling. Since it always retains both pedals and a discrete connected drive for rider-powered propulsion, the motorized...

such as the Velosolex affords the rider to cycle under human power or with the assistance of a 49 cm³ (3 cu in) engine which equates to a range of 160 to-. Electric pedal assisted bikes run on as little as 1 kWh/100 km, while maintaining speeds in excess of 30 km/h (18.6 mph). These best-case figures rely on a human doing 70% of the work, with around 3.6 MJ/100 km coming from the engine.

Human power

Including the human energy dramatically changes the efficiency of cycles quoted above. As with walking, this would include the increase in food consumption due to caloric efficiency of human muscle and cardio vascular efficiency. However, only the rise in food consumption above the diet of a non-cyclist should be considered.

To be thorough, a comparison must also consider the energy costs of producing, transporting and packaging of fuel (food or fossil fuel), the energy incurred in disposing of exhaust waste, and the energy costs of manufacturing the vehicle. This last can be significant given that walking requires little or no special equipment, while automobiles, for example, require a great deal of energy to produce and have relatively short life-spans. Also any comparison of electric vehicles and liquid-fuelled vehicles must include the fuel consumed in the power station to generate the electricity. In the UK for instance the efficiency of the electricity generation and distribution system is around 0.40.

Automobiles

Automobile fuel efficiency is often expressed in volume fuel consumed per one hundred kilometres (i.e., L/100 km) but in distance per volume fuel consumed (i.e., miles per gallon) in the US. This is complicated by the different energy content of fuels (compare petrol and diesel). The Oak Ridge National Laboratory (ORNL) state that the energy content of unleaded gasoline is 115,000 BTU per US gallon (32 MJ/L) compared to 130,500 BTU per US gallon (36.4 MJ/L) for diesel.

A second important consideration is the energy costs of producing these fuels. Bio-fuels, electricity

Electricity

Electricity is a general term encompassing a variety of phenomena resulting from the presence and flow of electric charge. These include many easily recognizable phenomena, such as lightning, static electricity, and the flow of electrical current in an electrical wire...

and hydrogen

Hydrogen

Hydrogen is the chemical element with atomic number 1. It is represented by the symbol H. With an average atomic weight of , hydrogen is the lightest and most abundant chemical element, constituting roughly 75% of the Universe's chemical elemental mass. Stars in the main sequence are mainly...

, for instance, have significant energy inputs in their production. Because of this, the 50-70% efficiency of hydrogen production

Hydrogen production

Hydrogen production is the family of industrial methods for generating hydrogen. Currently the dominant technology for direct production is steam reforming from hydrocarbons. Many other methods are known including electrolysis and thermolysis...

has to be combined with the vehicle efficiency to yield net efficiency.

A third consideration to take into account is the occupancy rate of the vehicle. As the number of passengers per vehicle increases the consumption per unit distance per vehicle increases. However this increase is slight compared to the reduction in consumption per unit distance per passenger. We can compare, for instance, the estimated average occupancy rate of about 1.3 passengers per car in the San Francisco Bay Area to the 2006 UK estimated average of 1.58.

Finally, vehicle energy efficiency calculations would be misleading without factoring the energy or "fuel" cost of producing the vehicle itself. This initial energy cost can of course be "amortized" over the life of the vehicle to calculate an average energy efficiency over its effective life span. In other words, vehicles that take a lot of energy or fuel to produce and are used for relatively short periods will require a great deal more energy over their effective lifespan than those that do not, and are therefore much less energy efficient than they may otherwise seem. Compare, for example, walking, which requires no special equipment at all, and an automobile, produced in and shipped from another country, and made from parts manufactured around the world from raw materials and minerals mined and processed elsewhere again, and used for a limited number of years.

Example consumption figures

Chevrolet Volt
Chevrolet Volt
The Chevrolet Volt is a plug-in hybrid electric vehicle manufactured by General Motors. The Volt has been on sale in the U.S. market since mid-December 2010, and is the most fuel-efficient compact car sold in the United States, as rated by the United States Environmental Protection Agency...

in full electric mode uses 36 kWh per 100 miles (810 kJ/km), meaning it may be more fuel-efficient than walking for 4 or more passenges. Note that the fuel at the power station is more than this by approximately 2.5 times.
The Daihatsu Charade
Daihatsu Charade
The Daihatsu Charade is a supermini which was first introduced in 1977. Daihatsu considers the Charade a "large compact" car to differentiate it from smaller compacts in its lineup, such as the Daihatsu Mira/Cuore...

993cc Turbo diesel (1987–1993) won the most fuel efficient vehicle award for going round the UK doing an average 100MPG. It was only surpassed recently by the VW Lupo 3L which gives about 102MPG. Both cars are surprisingly rare to find on the popular market.
The Volkswagen Polo 1.4 TDI Bluemotion and the SEAT Ibiza 1.4 TDI Ecomotion, both rated at 3.8 L/100 km (combined) are the most fuel efficient cars on sale in the UK as of 22 March 2008.

Honda Insight
Honda Insight
The Honda Insight is a hybrid electric vehicle manufactured by Honda and the first production vehicle to feature Honda's Integrated Motor Assist system. The first-generation Insight was produced from 1999 to 2006 as a three-door hatchback...

- achieves 48 mpgU.S. (20.4 km/L) under real-world conditions.
Honda Civic Hybrid
Honda Civic Hybrid
The Civic hybrid, based on the seventh generation Civic, was first introduced to the Japanese market in December 2001. Honda claimed it was the most fuel efficient 5-passenger gasoline-powered production vehicle in the world at the time. It was introduced to the U.S. in spring 2002 as a 2003 model...

- regularly averages around 45 mpgU.S. (19.1 km/L).
Toyota Prius
Toyota Prius
The Toyota Prius is a full hybrid electric mid-size hatchback, formerly a compact sedan developed and manufactured by the Toyota Motor Corporation...

- According to the US EPA's revised estimates, the combined fuel consumption for the 2008 Prius is 46 mpgU.S. (19.6 km/L), making it the most fuel efficient US car of 2008 according to the EPA. In the UK, the official fuel consumption figure (combined) for the Prius is 4.3 L/100 km.
The General Motors EV1
General Motors EV1
The General Motors EV1 was an electric car produced and leased by the General Motors Corporation from 1996 to 1999. It was the first mass-produced and purpose-designed electric vehicle of the modern era from a major automaker, and the first GM car designed to be an electric vehicle from the...

was rated in a test with a charging efficiency of 373 Wh-AC/mile or 23 kWh/100 km (translates approximately to 2.6L/100 km).
The four passenger GEM
Global Electric Motorcars
Global Electric Motorcars , a wholly owned subsidiary of Polaris Industries, is a U.S. manufacturer in the low-speed vehicle category, producing neighborhood electric vehicles since 1998 and has sold more than 45,000 GEM battery-electric vehicles worldwide as of December 2010.Until June 2011, GEM...

NER
Neighborhood electric vehicle
A Neighborhood Electric Vehicle is a U.S. denomination for battery electric vehicles that are legally limited to roads with posted speed limits as high as depending on the particular laws of the state, usually are built to have a top speed of , and have a maximum loaded weight of 3,000 lbs...

also uses 169 Wh/mile or 10.4 kWh/100 km, which equates to 2.6 kWh/100 km per person when fully occupied, albeit at only 24 mph (38.6 km/h). All these electric vehicle figures are overoptimistic though, taking into account the coal, oil or natural gas consumed in the power station due to modern high density fossil fuel electricity generating plants 67% thermal efficiency of converting fuel into electricity at best.

Aircraft

A principal determinant of fuel consumption in aircraft is drag

Drag (physics)

In fluid dynamics, drag refers to forces which act on a solid object in the direction of the relative fluid flow velocity...

, which must be opposed by thrust for the aircraft to progress. Drag is proportional to the lift

Lift (force)

A fluid flowing past the surface of a body exerts a surface force on it. Lift is the component of this force that is perpendicular to the oncoming flow direction. It contrasts with the drag force, which is the component of the surface force parallel to the flow direction...

required for flight, which is equal to the weight of the aircraft. However, beginning at transonic

Transonic

Transonic speed is an aeronautics term referring to the condition of flight in which a range of velocities of airflow exist surrounding and flowing past an air vehicle or an airfoil that are concurrently below, at, and above the speed of sound in the range of Mach 0.8 to 1.2, i.e. 600–900 mph...

speeds of around Mach 0.85, shockwaves form increasing drag. For supersonic flight, it is difficult to achieve a lift to drag ratio greater than five and fuel consumption is increased in proportion.

As induced drag increases with weight, mass reduction, with improvements in engine efficiency and reductions in aerodynamic drag, has been a principal source of efficiency gains in aircraft, with a rule-of-thumb being that a 1% weight reduction corresponds to around a .75% reduction in fuel consumption. Flight altitude affects both parasitic drag and engine efficiency. Jet-engine efficiency increases at altitude up to the tropopause

Tropopause

The tropopause is the atmospheric boundary between the troposphere and the stratosphere.-Definition:Going upward from the surface, it is the point where air ceases to cool with height, and becomes almost completely dry...

, the temperature minimum of the atmosphere; at lower temperatures, the Carnot efficiency is higher. Jet engine efficiency is also increased at high speeds, but above about Mach 0.85 the airframe aerodynamic losses increase faster.
Passenger airplanes averaged 4.8 L/100 km per passenger (1.4 MJ/passenger-km) (49 passenger-miles per gallon) in 1998. Note that on average 20% of seats are left unoccupied. Jet aircraft efficiencies are improving: Between 1960 and 2000 there was a 55% overall fuel efficiency gain (if one were to exclude the inefficient and limited fleet of the DH Comet 4 and to consider the Boeing 707 as the base case). Most of the improvements in efficiency were gained in the first decade when jet craft first came into widespread commercial use. Compared to the most advanced turboprop aircraft of the 1950s, the modern aircraft is only marginally more efficient per passenger-mile. Between 1971 and 1998 the fleet-average annual improvement per available seat-kilometre
was estimated at 2.4%. As over 80% of the fully laden take-off weight of a modern aircraft such as the Airbus A380

Airbus A380

The Airbus A380 is a double-deck, wide-body, four-engine jet airliner manufactured by the European corporation Airbus, a subsidiary of EADS. It is the largest passenger airliner in the world. Due to its size, many airports had to modify and improve facilities to accommodate it...

is craft and fuel, there remains considerable room for future improvements in efficiency.

Airbus
Airbus
Airbus SAS is an aircraft manufacturing subsidiary of EADS, a European aerospace company. Based in Blagnac, France, surburb of Toulouse, and with significant activity across Europe, the company produces around half of the world's jet airliners....

state that their A380
Airbus A380
The Airbus A380 is a double-deck, wide-body, four-engine jet airliner manufactured by the European corporation Airbus, a subsidiary of EADS. It is the largest passenger airliner in the world. Due to its size, many airports had to modify and improve facilities to accommodate it...

consumes fuel at the rate of less than 3 L/100 km per passenger. CNN reports that the fuel consumption figures provided by Airbus for the A380, given as 2.9 L/100 km per passenger, are "slightly misleading", because they assume a passenger count of 555, but do not allow for any luggage or cargo. Typical occupancy figures are unknown at this time.

NASA and Boeing are conducting tests on a 500 lb (226.8 kg) "blended wing
Blended wing body
Blended Wing Body aircraft have a flattened and airfoil shaped body, which produces most of the lift, the wings contributing the balance. The body form is composed of distinct and separate wing structures, though the wings are smoothly blended into the body...

" aircraft. This design allows for greater fuel efficiency since the whole craft produces lift, not just the wings.

The Sikorsky S-76C++
Sikorsky S-76
The Sikorsky S-76 is an American medium-size commercial utility helicopter. The S-76 is powered by two turboshaft engines, which drive both the main and tail rotors, each with four blades...

twin turbine helicopter gets about 1.65 mpgU.S. (0.70148707695 km/L) at 140 knots (76.2 m/s) and carries 12 for about 19.8 passenger-miles per gallon (11.9 litres per 100 passenger-kilometres).

The Bell 407 single-engine turbine helicopter burns 51 gallons per hour at 120 knots carrying one pilot and six passengers. 2.35 NM per gal for 14.1 passenger-miles per gallon. If the pilot is counted as a passenger, it's 16.4 people-miles per gallon. Increased altitudes can yield better fuel rates. It has operated at 47 gal/hr.

Concorde
Concorde
Aérospatiale-BAC Concorde was a turbojet-powered supersonic passenger airliner, a supersonic transport . It was a product of an Anglo-French government treaty, combining the manufacturing efforts of Aérospatiale and the British Aircraft Corporation...

the supersonic transport
Supersonic transport
A supersonic transport is a civilian supersonic aircraft designed to transport passengers at speeds greater than the speed of sound. The only SSTs to see regular service to date have been Concorde and the Tupolev Tu-144. The last passenger flight of the Tu-144 was in June 1978 with its last ever...

managed about 17 miles to the gallon per passenger; similar to a business jet, but much worse than a subsonic turbofan aircraft.

Related to fuel efficiency is the impact of aviation emissions on climate.

Small Aircraft

Small aircraft equipped with atmospheric piston engines can't be compared to jet air passenger aircraft. They're low power, low altitude, low speed, low capacity aerial vehicles.
Motor-gliders made of composite materials can reach an extremely low fuel consumption for cross-country flights, using thermal air currents and winds. Under continuous motorised flight at 225 km/h, a Pipistrel Sinus burns 11 liters of fuel per flight hour. Carrying 2 people aboard, it operates at 0.6 Gal/100 p.km (2.4 l/100p.km). Old generation World War II aircraft can be up to 50 l/100p.km.

Ships

Cunard
Cunard Line
Cunard Line is a British-American owned shipping company based at Carnival House in Southampton, England and operated by Carnival UK. It has been a leading operator of passenger ships on the North Atlantic for over a century...

states that their liner, the RMS Queen Elizabeth 2
RMS Queen Elizabeth 2
Queen Elizabeth 2, often referred to simply as the QE2, is an ocean liner that was operated by Cunard from 1969 to 2008. Following her retirement from cruising, she is now owned by Istithmar...

, travels 49.5 feet per imperial gallon of diesel oil (3.32 m/L or 41.2 ft/US gal), and that it has a passenger capacity of 1777. Thus carrying 1777 passengers we can calculate an efficiency of 16.7 passenger-miles per imperial gallon (16.9 L/100 p·km or 13.9 p·mpg_–US).

Trains

Trains can be an efficient means of transport for freight and passengers. Efficiency varies significantly with passenger loads and, losses incurred in electricity generation and supply (for electrified systems), and, importantly, end-to-end delivery, where stations are not the originating final destinations of a journey.

Actual consumption depends on gradients, maximum speeds, loading and stopping patterns. Data produced for the European MEET project (Methodologies for Estimating Air Pollutant Emissions) illustrate the different consumption patterns over several track sections. The results show the consumption for a German ICE high-speed train varied from around 19 to-. The data also reflects the weight of the train per passenger. For example, the TGV

TGV

The TGV is France's high-speed rail service, currently operated by SNCF Voyages, the long-distance rail branch of SNCF, the French national rail operator....

double-deck ‘Duplex’ trains use lightweight materials which keep axle loads down and reduce damage to track but also save energy.

Freight

Energy consumption estimates for rail freight vary widely, and many are provided by interested parties. Some are tabulated below.

Source	country	year	fuel/tonne	MJ/tonne	ref
Association of American Railroads Association of American Railroads The Association of American Railroads is an industry trade group representing primarily the major freight railroads of North America . Amtrak and some regional commuter railroads are also members...	USA	2007	436 mi/gal Gallon The gallon is a measure of volume. Historically it has had many different definitions, but there are three definitions in current use: the imperial gallon which is used in the United Kingdom and semi-officially within Canada, the United States liquid gallon and the lesser used United States dry... (166 km/l)/short ton Short ton The short ton is a unit of mass equal to . In the United States it is often called simply ton without distinguishing it from the metric ton or the long ton ; rather, the other two are specifically noted. There are, however, some U.S... (907.2 kg)	need MJ
Network Rail Network Rail Network Rail is the government-created owner and operator of most of the rail infrastructure in Great Britain .; it is not responsible for railway infrastructure in Northern Ireland...	UK	Year	87 km/l Litre pic\|200px\|right\|thumb\|One litre is equivalent to this cubeEach side is 10 cm1 litre water = 1 kilogram water The litre is a metric system unit of volume equal to 1 cubic decimetre , to 1,000 cubic centimetres , and to 1/1,000 cubic metre... per tonne of goods	need MJ

Passenger

Source	country	year	Train Efficiency	Per passenger km	ref
East Japan Railway Company East Japan Railway Company is the largest passenger railway company in the world and one of the seven Japan Railways Group companies. The company name is officially abbreviated as JR East in English, and as in Japanese. The company's headquarters are in Yoyogi, Shibuya, Tokyo....	Japan	2004	20.6 MJ/car-km	0.35 MJ/passenger-km
EC European Commission The European Commission is the executive body of the European Union. The body is responsible for proposing legislation, implementing decisions, upholding the Union's treaties and the general day-to-day running of the Union....	EC	1997	18.00 kWh/train-km	64.80 MJ/train-km	TGV Duplex assuming 3 intermediate stops between Paris and Lyon Lyon Lyon , is a city in east-central France in the Rhône-Alpes region, situated between Paris and Marseille. Lyon is located at from Paris, from Marseille, from Geneva, from Turin, and from Barcelona. The residents of the city are called Lyonnais.... .
Colorado Rail	USA	year	1.125 mpgU.S. (0.478286643375 km/L)	468 passenger-miles/US gallon (0.503 L/100 passenger-km)	Colorado Railcar Colorado Railcar Colorado Railcar was a manufacturer of railroad rolling stock, railcars and diesel multiple unit commuter vehicles. Both products come in single- and double-level versions. It shut down in 2008, with its assets being purchased by US Railcar.-History:... double-deck DMU Diesel multiple unit A diesel multiple unit or DMU is a multiple unit train consisting of multiple carriages powered by one or more on-board diesel engines. They may also be referred to as a railcar or railmotor, depending on country.-Design:... hauling two Bombardier Bi-level coaches Bombardier BiLevel Coach Bombardier BiLevel coaches are bilevel passenger cars designed to carry up to 360 passengers for regional railways. These carriages are easily identifiable; they are double-decked and are shaped like elongated octagons.-History:...
SBB-CFF-FFS SBB-CFF-FFS Swiss Federal Railways and SFR are not in official use) is the national railway company of Switzerland headquartered in Bern. Formerly a government institution, it is since 1999 a special stock corporation with all shares held by the Swiss Confederation or the Swiss cantons...	Switzerland	year	0.082 kWh/passenger-km for traction	need coversion	no ref
Siemens Siemens AG Siemens AG is a German multinational conglomerate company headquartered in Munich, Germany. It is the largest Europe-based electronics and electrical engineering company....	Basel, Switzerland	year	1.53 kWh/vehicle-km (5.51 MJ/vehicle-km)	0.085 MJ/passenger-km (0.15 MJ/passenger-km at 80% average load
Amtrak Amtrak The National Railroad Passenger Corporation, doing business as Amtrak , is a government-owned corporation that was organized on May 1, 1971, to provide intercity passenger train service in the United States. "Amtrak" is a portmanteau of the words "America" and "track". It is headquartered at Union...	USA	2005		2,935 BTU/passenger-mile (1.9 MJ/passenger-km)

Braking losses

Stopping is a considerable source of inefficiency. Modern electric trains like the Shinkansen
Shinkansen
The , also known as THE BULLET TRAIN, is a network of high-speed railway lines in Japan operated by four Japan Railways Group companies. Starting with the Tōkaidō Shinkansen in 1964, the network has expanded to currently consist of of lines with maximum speeds of , of Mini-shinkansen with a...

(the Bullet Train) use regenerative braking to return current into the catenary

Overhead lines

Overhead lines or overhead wires are used to transmit electrical energy to trams, trolleybuses or trains at a distance from the energy supply point...

while they brake. A Siemens study indicated that regenerative braking might recover 41.6% of the total energy consumed. The Passenger Rail (Urban and Intercity) and Scheduled Intercity and All Charter Bus Industries Technological and Operational Improvements - FINAL REPORT states that "Commuter operations can dissipate more than half of their total traction energy in braking for stops." and that "We estimate hotel power

Hotel Electric Power

Hotel Electric Power is a maritime term referring to electricity generated and used aboard a ship for purposes other than propulsion such as lighting, communications, climate control, refrigeration, water desalination and treatment, entertainment, etc...

to be 35 percent (but it could possibly be as high as 45 percent) of total energy consumed by commuter railways." Having to accelerate and decelerate a heavy train load of people at every stop is inefficient despite regenerative braking which can recover typically around 20% of the energy wasted in braking. Weight is an determinant of braking losses.

Other references

AEA study of road and rail for the United Kingdom Department for Transport: Final report

Buses

In July 2005, the average occupancy for buses in the UK was stated to be 9.

The fleet of 244 40 feet (12.2 m) 1982 New Flyer trolley buses in local service with BC Transit
BC Transit
BC Transit is a provincial crown agency responsible for coordinating the delivery of public transportation within British Columbia, Canada, outside of Greater Vancouver...

in Vancouver, Canada, in 1994/95 consumed 35454170 kW·h 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 people standing on Vancouver trolleybuses. Note that this is a local transit service with many stops per kilometre; part of the reason for the efficiency is the use of regenerative braking.

A diesel bus commuter service in Santa Barbara, California
Santa Barbara, California
Santa Barbara is the county seat of Santa Barbara County, California, United States. Situated on an east-west trending section of coastline, the longest such section on the West Coast of the United States, the city lies between the steeply-rising Santa Ynez Mountains and the Pacific Ocean...

, USA, found average diesel bus efficiency of 6 mpgU.S. (2.6 km/L) (using MCI
Motor Coach Industries
Motor Coach Industries International Inc. is an American bus manufacturer based in Schaumburg, Illinois, and is a leading participant in the North American coach bus industry. It has various operating subsidiaries:...

102DL3 buses). With all 55 seats filled this equates to 330 passenger-mpg, with 70% filled the efficiency would be 231 passenger-mpg. At the typical average passenger load of 9 people, the efficiency is only 54 passenger-mpg and could be half of this figure when many stops are made in urban routes.

Rockets

Unlike other forms of transportation, rockets are commonly designed for putting objects into orbit. Once in sufficiently high orbit, objects have almost negligible air drag, and the orbits decay so slowly that a satellite

Prospero X-3

-External links:* from "Woomera on the Web"* from Encyclopedia Astronautica* in the Global Frequency Database...

can be still orbiting decades after launch. For these reasons rocket and space propulsion efficiency is rarely measured in terms of distance per unit of fuel, but in terms of specific impulse

Specific impulse

Specific impulse is a way to describe the efficiency of rocket and jet engines. It represents the derivative of the impulse with respect to amount of propellant used, i.e., the thrust divided by the amount of propellant used per unit time. If the "amount" of propellant is given in terms of mass ,...

which gives how much change in momentum (i.e. impulse) can be obtained from a unit of propellant.

However, to give a concrete example, NASA

NASA

The National Aeronautics and Space Administration is the agency of the United States government that is responsible for the nation's civilian space program and for aeronautics and aerospace research...

's space shuttle

Space Shuttle

The Space Shuttle was a manned orbital rocket and spacecraft system operated by NASA on 135 missions from 1981 to 2011. The system combined rocket launch, orbital spacecraft, and re-entry spaceplane with modular add-ons...

fires its engines for around 8.5 minutes, consuming 1,000 tons of solid propellant (containing 16% aluminium) and an additional 2,000,000 litres of liquid propellant (106,261 kg of liquid hydrogen

Liquid hydrogen

Liquid hydrogen is the liquid state of the element hydrogen. Hydrogen is found naturally in the molecular H2 form.To exist as a liquid, H2 must be pressurized above and cooled below hydrogen's Critical point. However, for hydrogen to be in a full liquid state without boiling off, it needs to be...

fuel) to lift the 100,000 kg vehicle (including the 25,000 kg payload) to an altitude of 111 km and an orbital velocity

Velocity

In physics, velocity is speed in a given direction. Speed describes only how fast an object is moving, whereas velocity gives both the speed and direction of the object's motion. To have a constant velocity, an object must have a constant speed and motion in a constant direction. Constant ...

of 30,000 km/h. With a specific energy

Specific energy

Specific energy is defined as the energy per unit mass. Common metric units are J/kg. It is an intensive property. Contrast this with energy, which is an extensive property. There are two main types of specific energy: potential energy and specific kinetic energy. Others are the gray and sievert,...

of 31MJ per kg for aluminum and 143 MJ/kg for liquid hydrogen, this means that the vehicle consumes around 5 TJ of solid propellant and 15 TJ of hydrogen fuel.

Once in orbit at 200 km and around 7.8 km/s velocity, the orbiter requires no further fuel. At this altitude and velocity, the vehicle has a kinetic energy of about 3 TJ and a potential energy of roughly 200 GJ. Given the energy input of 20 TJ, the Space Shuttle is about 16% energy efficient at launching the orbiter and payload just 4% efficiency if the payload alone is considered.
If the Space Shuttle were used to transport people or freight from a point to another on the Earth, using the theoretical largest ground distance (antipodal) flight of 20,000 km, energy usage would be about 40 kJ/km/kg of payload.

Other

NASA
NASA
The National Aeronautics and Space Administration is the agency of the United States government that is responsible for the nation's civilian space program and for aeronautics and aerospace research...

's Crawler-Transporter
Crawler-Transporter
The crawler-transporters are a pair of tracked vehicles used to transport spacecraft from NASA's Vehicle Assembly Building along the Crawlerway to Launch Complex 39. They were originally used to transport the Saturn IB and Saturn V rockets during the Apollo, Skylab and Apollo–Soyuz programs....

is used to move the Shuttle from storage to the launch pad. It uses diesel and has one of the highest fuel consumption rates on record, 150 USgal/mi.

UK Public transport

Rail and bus are generally required to serve 'off peak' and rural services, which by their nature have lower loads than city bus routes and inter city train lines. Moreover, due to their 'walk on' ticketing it is much harder to match daily demand and passenger numbers. As a consequence, the overall load factor on UK railways is 35% or 90 people per train:

Conversely, Air services work on point-to-point networks between large population centres and are 'pre-book' in nature. Using Yield management

Yield management

Revenue management is the process of understanding, anticipating and influencing consumer behavior in order to maximize yield or profits from a fixed, perishable resource...

overall loads can be raised to around 70-90%. However, recently intercity train operators have been using similar techniques, with loads reaching typically 71% overall for TGV

TGV

The TGV is France's high-speed rail service, currently operated by SNCF Voyages, the long-distance rail branch of SNCF, the French national rail operator....

services in France and a similar figure for the UK's Virgin trains

Virgin Trains

Virgin Trains is a train operating company in the United Kingdom. It operates long-distance passenger services on the West Coast Main Line between London, the West Midlands, North West England, North Wales and Scotland...

services.

For emissions, the electricity generating source needs to be taken into account. Up to date figures for the UK can be found here:

http://www.atoc-comms.org/admin/userfiles/Energy20%&%20Emissions%20Statement%20-%20web%20version.pdf

(Bad link)

http://www.aef.org.uk/downloads//Grams_CO2_transportmodesUK.pdf

US Passenger transportation

The US Transportation Energy Data Book states the following figures for
Passenger transportation in 2006:

Transport mode	Average passengers per vehicle	BTU per passenger-mile
Vanpool	6.1	1322 BTU/mi
Efficient Hybrid	1.57	1659 BTU/mi
Motorcycles	1.2	1855 BTU/mi
Rail (Intercity Amtrak Amtrak The National Railroad Passenger Corporation, doing business as Amtrak , is a government-owned corporation that was organized on May 1, 1971, to provide intercity passenger train service in the United States. "Amtrak" is a portmanteau of the words "America" and "track". It is headquartered at Union... )	20.5	2650 BTU/mi
Rail (Transit Light & Heavy)	22.5	2784 BTU/mi
Rail (Commuter)	31.3	2996 BTU/mi
Air	96.2	3261 BTU/mi
Cars	1.59	3512 BTU/mi
Personal Trucks	1.72	3944 BTU/mi
Buses (Transit)	8.8	4235 BTU/mi

US Freight transportation

The US Transportation Energy book states the following figures for Freight transportation in 2004:

Transportation mode	Fuel consumption
Transportation mode	BTU per short ton mile	kJ per tonne kilometre
Class 1 Railroads	341
Domestic Waterborne	510
Heavy Trucks	3,357
Air freight (approx)	9,600

Compare:

Space Shuttle used to transport freight to the other side of the Earth (see above): 40,000 kJ per tonne kilometre.
Net energy for lifting: 10,000 kJ per tonne kilometre.

Caveats

Comparing fuel efficiency in transportation is like comparing apples and oranges. Here are a few things to consider. Traction energy Metrics produced by the UK Rail and Safety Standards Board is also a useful review of the problem of comparison http://www.rssb.co.uk/pdf/reports/research/T618_traction-energy-metrics_final.pdf

There is a distinction between vehicle MPGe and passenger MPGe. Most of these entries cite passenger MPGe even if not explicitly stated. It is important not to compare energy figures that relate to unsimilar journeys. An airline jet cannot be used for an urban commute so when comparing aircraft with cars the car figures must take this into account.

There is currently no agreed upon method of comparing electric vehicle
Electric vehicle
An electric vehicle , also referred to as an electric drive vehicle, uses one or more electric motors or traction motors for propulsion...

efficiency to heat engine
Heat engine
In thermodynamics, a heat engine is a system that performs the conversion of heat or thermal energy to mechanical work. It does this by bringing a working substance from a high temperature state to a lower temperature state. A heat "source" generates thermal energy that brings the working substance...

(fossil fuel
Fossil fuel
Fossil fuels are fuels formed by natural processes such as anaerobic decomposition of buried dead organisms. The age of the organisms and their resulting fossil fuels is typically millions of years, and sometimes exceeds 650 million years...

) vehicle efficiency. However, current typical emissions and thermal energy consumption can be compared. Vehicle speed is also an important parameter, and a peer-reviewed evaluation which convolves these criteria may be found at http://www.bentham.org/open/toefj/articles/V001/11TOEFJ.pdf

If the issue is rapid investment in new electric mass transit it is important to use emissions associated with the most polluting fuel because increased demand for electricity increases the use of polluting fuel used in generation for the immediate future, as well as low emissions fuels in the case of some countries.

Systems that re-use vehicles like trains and buses can't be directly compared to vehicles that get parked at their destination. They use energy to return (less full) for more passengers and must sometimes run on schedules and routes with little patronage. These factors greatly affect overall system efficiencies. The energy costs of accumulating load need to be included. In the case of most mass transit distributing and accumulating load over many stops means that passenger kilometres are inherently a small proportion of vehicle kilometres see Transport Energy Metrics, Lessons from the west Coast Main line Modernisation and figures for London Underground in transport statistics for Great Britain 2003. Lessons from the west coast mainline modernisation suggest that long passenger rail should operate at less than 40% capacity utilisation and for London underground the figure is probably less than 15%.

Most cars run at less than full capacity, with the usual average load being between 1 and 2. Cars are also subject to inefficiencies because of congestion and the need to negotiate road junctions. The impact of transport road building to reduce congestion should always be considered as should the improving efficiency of cars see http://www.hm-treasury.gov.uk/media/9/5/pbr_csr07_king840.pdf,

Vehicles are not isolated systems. They usually form a part of larger systems whose design inherently determines energy consumption. Judging the value of transport systems by comparing the performance of their vehicles alone can be misleading. For instance, metro
Rapid transit
A rapid transit, underground, subway, elevated railway, metro or metropolitan railway system is an electric passenger railway in an urban area with a high capacity and frequency, and grade separation from other traffic. Rapid transit systems are typically located either in underground tunnels or on...

systems may have a poor energy efficiency per passenger kilometre, but their high throughput and low physical footprint makes the existence of high urban population densities
Urban density
Urban density is a term used in urban planning and urban design to refer to the number of people inhabiting a given urbanized area. As such it is to be distinguished from other measures of population density. Urban density is considered an important factor in understanding how cities function...

viable. Total energy consumption per capita declines sharply as population density increases, since journeys become shorter.
See also Logistics and Transport Focus (the Journal of the Charter Institute of Transport)vol 9 number10 through volume 10 number 6 for a series of articles debating the general issues of fuel efficiency in transportation in the context of impact on climate change.

External links

ECCM Study for rail, road and air journeys between main UK cities http://www.businesstravelshow.com/ExhibitorLibrary/127/VirginTrainsEmissionsComparison.pdf
Flight Emission Calculator
Transport Energy Consumption Discussion Paper 2004 - Prof. Roger Kemp
Traction Summary Report 2007- Prof. Roger Kemp
Transportation Energy Data Book (US)
Fuel Consumption Ratings

The source of this article is wikipedia, the free encyclopedia. The text of this article is licensed under the GFDL.