Discussing what form of transport is the most fuel efficient and economical.
The energy efficiency in transport is the useful travelled distance, of passengers, goods or any type of load; divided by the total energy put into the transport propulsion means. The energy input might be rendered in several different types depending on the type of propulsion, and normally such energy is presented in liquid fuels, electrical energy or food energy. The energy efficiency is also occasionally known as energy intensity. The inverse of the energy efficiency in transport is the energy consumption in transport.
Energy efficiency in transport is often described in terms of fuel consumption, fuel consumption being the reciprocal of fuel economy. Nonetheless, fuel consumption is linked with a means of propulsion which uses liquid fuels, whilst energy efficiency is applicable to any sort of propulsion. To avoid said confusion, and to be able to compare the energy efficiency in any type of vehicle, experts tend to measure the energy in the International System of Units, i.e., joules.
Therefore, in the International System of Units, the energy efficiency in transport is measured in terms of metre per joule, or m/J, while the energy consumption in transport is measured in terms of joules per metre, or J/m. The more efficient the vehicle, the more metres it covers with one joule (more efficiency), or the fewer joules it uses to travel over one metre (less consumption). The energy efficiency in transport largely varies by means of transport. Different types of transport range from some hundred kilojoules per kilometre (kJ/km) for a bicycle to tens of megajoules per kilometre (MJ/km) for a helicopter.
Via type of fuel used and rate of fuel consumption, energy efficiency is also often related to operating cost ($/km) and environmental emissions (e.g. CO2/km).
Units of measurement.
In the International System of Units, the energy efficiency in transport is measured in terms of metre per joule, or m/J. Nonetheless, several conversions are applicable, depending on the unit of distance and on the unit of energy. For liquid fuels, normally the quantity of energy input is measured in terms of the liquid's volume, such as litres or gallons. For propulsion which runs on electricity, normally kWh is used, while for any type of human-propelled vehicle, the energy input is measured in terms of Calories. It is typical to convert between different types of energy and units.
For passenger transport, the energy efficiency is normally measured in terms of passengers times distance per unit of energy, in the SI, passengers metres per joule (pax.m/J); while for cargo transport the energy efficiency is normally measured in terms of the mass of transported cargo times distance per unit of energy, in the SI, kilograms metres per joule (kg.m/J). Volumetric efficiency with respect to vehicle capacity may also be reported, such as passenger-mile per gallon (PMPG), obtained by multiplying the miles per gallon of fuel by either the passenger capacity or the average occupancy. The occupancy of personal vehicles is typically lower than capacity by a considerable degree and thus the values computed based on capacity and on occupancy will often be quite different.
Liquid fuels.
Energy efficiency is expressed in terms of fuel economy:
Energy consumption (reciprocal efficiency) is expressed terms of fuel consumption:
Electricity.
Electricity consumption:
Producing electricity from fuel requires much more primary energy than the amount of electricity produced.
Food energy.
Energy consumption:
Land Passenger Transport.
Table Overview.
In the following table the energy efficiency and energy consumption for different types of passenger land vehicles and modes of transport, as well as standard occupancy rates, are presented. The sources for these figures are in the correspondent section for each vehicle, in the following article. The conversions amongst different types of units, are well known in the art.
For the conversion amongst units of energy in the following table, 1 litre of petrol amounts to 34.2 MJ, 1 kWh amounts to 3.6 MJ and 1 kilocalorie amounts to 4184 J. For the car occupation ratio, the value of 1.2 passengers per automobile was considered. Nonetheless, in Europe this value slightly increases to 1.4. The sources for conversions amongst units of measurements appear only of the first row.
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Land transport means.
Walking.
A person walking at requires approximately of food energy per hour, which is equivalent to 4.55 km/MJ. of petrol contains about of energy, so this is approximately equivalent to .
Velomobile.
Velomobiles (enclosed recumbent bicycles) have the highest energy efficiency of any known mode of personal transport because of their small frontal area and aerodynamic shape. At a speed of , the velomobile manufacturer WAW claims that only 0.5 kWh (1.8 MJ) of energy per 100 km is needed to transport the passenger (= 18 J/m). This is around ;templatestyles src="Fraction/styles.css" / ;1⁄5 (20%) of what is needed to power a standard upright bicycle without aerodynamic cladding at same speed, and ;templatestyles src="Fraction/styles.css" / ;1⁄50 (2%) of that which is consumed by an average fossil fuel or electric car (the velomobile efficiency corresponds to 4700 miles per US gallon, 2000 km/L, or 0.05 L/100 km). Real energy from food used by human is 4–5 times more. Unfortunately their energy efficiency advantage over bicycles becomes smaller with decreasing speed and disappears at around 10 km/h where power needed for velomobiles and triathlon bikes are almost the same.
Bicycle.
A standard lightweight, moderate-speed bicycle is one of the most energy-efficient forms of transport. Compared with walking, a cyclist riding at requires about half the food energy per unit distance: 27 kcal/km, per 100 km, or 43 kcal/mi. This converts to about . This means that a bicycle will use between 10 and 25 times less energy per distance travelled than a personal car, depending on fuel source and size of the car. This figure does depend on the speed and mass of the rider: greater speeds give higher air drag and heavier riders consume more energy per unit distance. In addition, because bicycles are very lightweight (usually between 7–15 kg) this means they consume very low amounts of materials and energy to manufacture. In comparison to an automobile weighing 1500 kg or more, a bicycle typically requires 100–200 times less energy to produce than an automobile. In addition, bicycles require less space both to park and to operate and they damage road surfaces less, adding an infrastructural factor of efficiency.
Motorised bicycle.
A motorised bicycle allows human power and the assistance of a engine, giving a range of . Electric pedal-assisted bikes run on as little as per 100 km, while maintaining speeds in excess of . These best-case figures rely on a human doing 70% of the work, with around per 100 km coming from the motor. This makes an electric bicycle one of the most efficient possible motorised vehicles, behind only a motorised velomobile and an electric unicycle (EUC).
Electric kick scooter.
Electric kick scooters, such as those used by scooter-sharing systems like Bird or Lime, typically have a maximum range of under and are commonly limited to a maximum speed of . Intended to fit into a last mile niche and be ridden in bike lanes, they require little skill from the rider. Because of their light weight and small motors, they are extremely energy-efficient with a typical energy efficiency of 1.1 kWh (4.0 MJ) per 100 km (1904 MPGe 810 km/L 0.124 L/100 km), even more efficient than bicycles and walking. However, as they must be recharged frequently, they are often collected overnight with motor vehicles, somewhat negating this efficiency. The lifecycle of electric scooters is also notably shorter than that of bicycles, often reaching only a single digit number of years.
Electric Unicycle.
An electric unicycle (EUC) cross electric skateboard variant called the Onewheel Pint can carry a 50 kg person 21.5 km at an average speed of 20 km/h. The battery holds 148Wh. Without taking energy lost to heat in the charging stage into account, this equates to an efficiency of 6.88Wh/km or 0.688kWh/100 km. Additionally, with regenerative braking as a standard design feature, hilly terrain would have less impact on an EUC compared to a vehicle with friction brakes such as a push bike. This combined with the single wheel ground interaction may make the EUC the most efficient known vehicle at low speeds (below 25 km/h), with the velomobile overtaking the position as most efficient at higher speeds due to superior aerodynamics.
Automobiles.
Automobiles are generally inefficient when compared to other modes of transport, due to the relatively high weight of the vehicle compared to its occupants. 
On a percentage basis, if there is one occupant in an automobile, only about 0.5% of the total energy used is used to move the person in the car, while the remaining 99.5% (about 200 times more) is used to move the car itself.
An important driver of energy consumption of cars per passenger is the occupancy rate of the vehicle. 
Although the consumption per unit distance per vehicle increases with increasing number of passengers, this increase is slight compared to the reduction in consumption per unit distance per passenger. 
This means that higher occupancy yields higher energy efficiency per passenger. 
Automobile occupancy varies across regions. For example, the estimated average occupancy rate is about 1.3 passengers per car in the San Francisco Bay Area, while the 2006 UK estimated average is 1.58.
Due to the efficiency of electric motors, electric cars are much more efficient than their internal combustion engine counterparts, consuming on the order of 38 megajoules (38 000 kJ) per 100 km in comparison to 142 megajoules per 100 km for combustion powered cars. However, depending on the way the electricity is generated, the actual primary energy use may be higher.
Driving practices and vehicles can be modified to improve their energy efficiency by about 15%.
Common efficiency measures.
Automobile fuel efficiency is most commonly expressed in terms of the volume of fuel consumed per one hundred kilometres (l/100 km), but in some countries (including the United States, the United Kingdom and India) it is more commonly expressed in terms of the distance per volume fuel consumed (km/L or miles per gallon). 
This is complicated by the different energy content of fuels such as petrol and diesel. 
The Oak Ridge National Laboratory (ORNL) states that the energy content of unleaded petrol is 115,000 British thermal unit (BTU) per US gallon (32 MJ/L) compared to 130,500 BTU per US gallon (36.4 MJ/L) for diesel.
Life-cycle energy use.
Automobiles have significant energy use in their life cycle, not directly attributable to the running of the vehicle.
An important consideration is the energy costs of producing the energy form used by the automobile. 
Bio-fuels, electricity and hydrogen, for instance, have significant energy inputs in their production. 
Hydrogen production efficiency are 50–70% when produced from natural gas, and 10–15% from electricity.
The efficiency of hydrogen production, as well as the energy required to store and transport hydrogen, must to be combined with the vehicle efficiency to yield net efficiency. 
Because of this, hydrogen automobiles are one of the least efficient means of passenger transport, generally around 50 times as much energy must be put into the production of hydrogen compared to how much is used to move the car.
Another important factor is the energy needed to build and maintain roads is an important consideration, as is the energy returned on energy invested (EROEI). 
Between these two factors, roughly 20% must be added to the energy of the fuel consumed, to accurately account for the total energy used.
Finally, vehicle energy efficiency calculations would be misleading without factoring the energy cost of producing the vehicle itself. 
This initial energy cost can of course be depreciated 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 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. Hybrid and electric cars use less energy in their operation than comparable petroleum-fuelled cars but more energy is used to manufacture them, so the overall difference would be less than immediately apparent. 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.
According to the French energy and environment agency ADEME, an average motor car has an embodied energy content of 20,800 kWh and an