The concept of vehicle-specific power (VSP) is a formalism used in the evaluation of

vehicle emissions Vehicle emissions control is the study of reducing the emissions produced by motor vehicles, especially internal combustion engines. Types of emissions Emissions of many air pollutants have been shown to have variety of negative effects on publi ...

. The idea was first developed by J. L. Jiménez at the

Massachusetts Institute of Technology The Massachusetts Institute of Technology (MIT) is a Private university, private Land-grant university, land-grant research university in Cambridge, Massachusetts. Established in 1861, MIT has played a key role in the development of modern t ...

. Informally, it is the sum of the loads resulting from aerodynamic drag, acceleration,

rolling resistance Rolling resistance, sometimes called rolling friction or rolling drag, is the force resisting the motion when a body (such as a ball, tire, or wheel) rolls on a surface. It is mainly caused by non-elastic effects; that is, not all the energy ...

, and hill climbing, all divided by the mass of the vehicle. Conventionally, it is reported in

kilowatt The watt (symbol: W) is the unit of power or radiant flux in the International System of Units (SI), equal to 1 joule per second or 1 kg⋅m2⋅s−3. It is used to quantify the rate of energy transfer. The watt is named after Jame ...

s per

tonne The tonne ( or ; symbol: t) is a unit of mass equal to 1000 kilograms. It is a non-SI unit accepted for use with SI. It is also referred to as a metric ton to distinguish it from the non-metric units of the short ton ( United State ...

, the

instantaneous power In physics, power is the amount of energy transferred or converted per unit time. In the International System of Units, the unit of power is the watt, equal to one joule per second. In older works, power is sometimes called ''activity''. Power ...

demand of the vehicle divided by its mass. VSP, combined with

dynamometer A dynamometer or "dyno" for short, is a device for simultaneously measuring the torque and rotational speed ( RPM) of an engine, motor or other rotating prime mover so that its instantaneous power may be calculated, and usually displayed by t ...

and remote-sensing measurements, can be used to determine vehicle emissions. The

United States Environmental Protection Agency The Environmental Protection Agency (EPA) is an independent executive agency of the United States federal government tasked with environmental protection matters. President Richard Nixon proposed the establishment of EPA on July 9, 1970; it ...

held a "modelling shootout" in 2001, to help with the development of its (then) new MOVES (motor vehicle emissions simulator) vehicle emissions model. Two of the four modelling metholodogies in the shootout, one from

North Carolina State University North Carolina State University (NC State) is a public land-grant research university in Raleigh, North Carolina. Founded in 1887 and part of the University of North Carolina system, it is the largest university in the Carolinas. The universi ...

and one internal to the EPA, used vehicle-specific power metrics. MOVES was eventually implemented using vehicle-specific power as its primary metric. (See for the EPA MOVES draft VSP specification.)

Formulae

Jiménez's own formula is: :

\mathrm = \frac = \frac

VSP can be simplified using typical coefficient values. Haibo Zhai of

provides the following formula for transit buses: : where: ;''v'':vehicle speed (in metres per second) ;''a'':vehicle acceleration (in metres per second per second) ;''g'':acceleration due to gravity ( gee, in metres per second per second) ;''φ'':road grade ;''ψ'':rolling resistance coefficient (metres per second per second) ;''ζ'':drag coefficient (reciprocal metres)

References

Cross-reference

Sources used

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Formulae

References

Cross-reference

Sources used

Further reading