The units of measurement in transportation describes the unit of measurement used to express various transportation quantities, as used in statistics, planning, and their related applications.
The currently popular units are:
Passenger-distance is the distance (km or miles) travelled by passengers on transit vehicles; determined by multiplying the number of unlinked passenger trips by the average length of their trips.
See main article: Passengers per hour per direction.
Passengers per hour per direction (pphpd) measures the maximum route capacity of a transport system.
A system may carry a high number of passengers per distance (km or mile) but a relatively low number of passengers per bus hour if vehicles operate in congested areas and thus travel at slower speed.
A transit system serving a community with a widely dispersed population must operate circuitous routes that tend to carry fewer passengers per distance (km or mile). A higher number is more favorable.
Freight is measured in mass-distance. A simple unit of freight is the kilogram-kilometre (kgkm), the service of moving one kilogram of payload a distance of one kilometre.
1 t = (1/0.907) short tons = 1.102 short tons.
The metric units (pkm and tkm) are used internationally. (In aviation where United States customary units are widely used, the International Air Transport Association (IATA) releases its statistics in the metric units.)
In the US, sometimes United States customary units are used.
The dimension of the measure is the product of the payload mass and the distance transported.
A semi truck traveling from Los Angeles to Chicago (approximate distance 2,015 miles) carrying 14 short tons of cargo delivers a service of 14 * 2,015 = 28,210 ton-miles of freight (equal to about 41,187 tkm).
Intermodal container traffic is commonly measured in twenty-foot equivalent units (TEUs), rather than cargo weight, e.g. a TEU-km would be the equivalent of one twenty-foot container transported one kilometer.[6]
Transportation density can be defined as the payload per period, say passenger / day or tonne / day. This can be used as the measure of intensity of the transportation on a particular section or point of transportation infrastructure, say road or railway. This can be used in comparison with the construction, running costs of the infrastructure.
Fatalities by VMT (vehicle miles traveled) is a unit for assessing road traffic fatalities. This metric is computed by dividing the fatalities by the estimated VMT.
Usually, transport risk is computed by reference to the distance traveled by people, while for road traffic risk, only vehicle traveled distance is usually taken into account.[7]
In the United States, the unit is used as an aggregate in yearly federal publications, while its usage is more sporadic in other countries. For instance, it appears to compare different kind of roads in some publications as it had been computed on a five-year period between 1995 and 2000.[8]
In the United States, it is computed per 100 million miles traveled, while internationally it is computed in 100 million or 1 billion kilometers traveled.
According to the Minnesota Department of Public Safety, Office of Traffic Safety
Energy efficiency in transport can be measured in L/100 km or miles per gallon (mpg). This can be normalized per vehicle, as in fuel economy in automobiles, or per seat, as for example in fuel economy in aircraft.
MacNeal 1994[9] discusses the history of this topic, exploring such units and how humans developed the current state of logically recognizing and naming them.