40 C.F.R. § 1037.805

Current through October 31, 2024
Section 1037.805 - Symbols, abbreviations, and acronyms

The procedures in this part generally follow either the International System of Units (SI) or the United States customary units, as detailed in NIST Special Publication 811 (incorporated by reference, see § 1037.810 ). See 40 CFR 1065.20 for specific provisions related to these conventions. This section summarizes the way we use symbols, units of measure, and other abbreviations.

(a)Symbols for chemical species. This part uses the following symbols for chemical species and exhaust constituents:

Table 1 to Paragraph (a) of § 1037.805 -Symbols for Chemical Species and Exhaust Constituents

Symbol Species
Ccarbon.
CH4methane.
COcarbon monoxide.
CO2carbon dioxide.
H2 Owater.
HChydrocarbon.
NMHCnonmethane hydrocarbon.
NMHCEnonmethane hydrocarbon equivalent.
NOnitric oxide.
NO2nitrogen dioxide.
NOXoxides of nitrogen.
N2 Onitrous oxide.
PMparticulate matter.
THCtotal hydrocarbon.
THCEtotal hydrocarbon equivalent.

(b)Symbols for quantities. This part 1037 uses the following symbols and units of measure for various quantities:

Table 2 to Paragraph (b) of § 1037.805 -Symbols for Quantities

Symbol Quantity Unit Unit symbolUnit in terms of SI base units
Avehicle frictional loadpound force or newtonlbf or Nkg·m·s-2.
aaxle position regression coefficient
[ALPHA]atomic hydrogen-to-carbon ratiomole per molemol/mol1.
[ALPHA]axle position regression coefficient
[ALPHA]0intercept of air speed correction
[ALPHA]1slope of air speed correction
agacceleration of Earth's gravitymeters per second squaredm/s2m·s-2.
a0intercept of least squares regression
a1slope of least squares regression
Bvehicle load from drag and rolling resistancepound force per mile per hour or newton second per meterlbf/(mi/hr) or N·s/mkg·s-1.
baxle position regression coefficient
[BETA]atomic oxygen-to-carbon ratiomole per molemol/mol1.
[BETA]axle position regression coefficient
[BETA]0intercept of air direction correction
[BETA]1slope of air direction correction
Cvehicle-specific aerodynamic effectspound force per mile per hour squared or newton-second squared per meter squaredlbf/mph2 or N·s2/m2kg·m-1.
caxle position regression coefficient
ciaxle test regression coefficients
Ciconstant
[DELTA]CdAdifferential drag areameter squaredm2m2.
CdAdrag areameter squaredm2m2.
Cddrag coefficient
CFcorrection factor
Crrcoefficient of rolling resistancenewton per kilonewtonN/kN10-3.
Ddistancemiles or metersmi or mm.
emass-weighted emission resultgrams per ton-mileg/ton-mig/kg-km.
Effefficiency
Fadjustment factor
Fforcepound force or newtonlbf or Nkg·m·s-2.
fnangular speed (shaft)revolutions per minuter/min [PI]·30·s-1.
Groad gradepercent%10-2.
ggravitational accelerationmeters per second squaredm/s2m·s-2.
helevation or heightmetersmm.
iindexing variable
kadrive axle ratio1.
kdtransmission gear ratio
ktopgearhighest available transmission gear
Lload over axlepound force or newtonlbf or Nkg·m·s-2.
mmasspound mass or kilogramlbm or kgkg.
Mmolar massgram per moleg/mol 10-3·kg·mol-1.
Mvehicle masskilogramkgkg.
Mevehicle effective masskilogramkgkg.
Mrotatinginertial mass of rotating componentskilogramkgkg.
Ntotal number in series
nnumber of tires
namount of substance ratemole per secondmol/smol·s-1.
PpowerkilowattkW 103·m2·kg·s- 3.
ppressurepascalPa kg·m-1·s-2.
[RHO]mass densitykilogram per cubic meterkg/m3kg·m-3.
PLpayloadtonstonkg.
[PHI]directiondegrees°°.
[PSI]directiondegrees°°.
rtire radiusmetermm.
r2coefficient of determination
Re#Reynolds number
SEEstandard error of the estimate
Astandard deviation
TRPMtire revolutions per milerevolutions per miler/mi
TRRLtire rolling resistance levelnewton per kilonewtonN/kN10-3.
Tabsolute temperaturekelvinKK.
TCelsius temperaturedegree Celsius°CK-273.15.
Ttorque (moment of force)newton meterN·m m2·kg·s-2.
ttimehour or secondhr or ss.
[DELTA]ttime interval, period, 1/frequencysecondss.
UFutility factor
vspeedmiles per hour or meters per secondmi/hr or m/sm·s-1.
wweighting factor
wwind speedmiles per hourmi/hrm·s-1.
Wworkkilowatt-hourkW·hr 3.6·m2·kg·s-1.
wCcarbon mass fractiongram per gramg/g1.
WRweight reductionpound masslbmkg.
xamount of substance mole fractionmole per mole mol/mol1.

(c)Superscripts. This part uses the following superscripts for modifying quantity symbols:

Table 3 to § 1037.805 -Superscripts

Superscript Meaning
overbar (such as y)arithmetic mean.
Double overbar (such as y)arithmetic mean of arithmetic mean.
overdot (such as y)quantity per unit time.

(d)Subscripts. This part uses the following subscripts for modifying quantity symbols:

Table 4 to Paragraph (d) of § 1037.805 -Subscripts

Subscript Meaning
±6±6° yaw angle sweep.
AA speed.
airair.
aeroaerodynamic.
altalternative.
actactual or measured condition.
airair.
axleaxle.
BB speed.
brakebrake.
CC speed.
Ccombdrycarbon from fuel per mole of dry exhaust.
CDcharge-depleting.
circuitcircuit.
CO2 DEFCO2 resulting from diesel exhaust fluid decomposition.
CO2 PTOCO2 emissions for PTO cycle.
coastdowncoastdown.
compcomposite.
CScharge-sustaining.
cycletest cycle.
drivedrive axle.
drive-idleidle with the transmission in drive.
driverdriver.
dynodynamometer.
effectiveeffective.
endend.
engengine.
eventevent.
fuelfuel.
fullfull.
gradegrade.
H2 OexhaustdryH2 O in exhaust per mole of exhaust.
hihigh.
ian individual of a series.
idleidle.
ininlet.
incincrement.
lolow.
lossloss.
maxmaximum.
measmeasured quantity.
medmedian.
minminimum.
movingmoving.
outoutlet.
Ppower.
pairpair of speed segments.
parked-idleidle with the transmission in park.
partialpartial.
plosspower loss.
plug-inplug-in hybrid electric vehicle.
powertrainpowertrain.
PTOpower take-off.
ratedrated speed.
recordrecord.
refreference quantity.
RLroad load.
rotatingrotating.
segsegment.
speedspeed.
spinaxle spin loss.
startstart.
steersteer axle.
ttire.
testtest.
ththeoretical.
totaltotal.
tractraction.
trac10traction force at 10 mi/hr.
trailertrailer axle.
transienttransient.
TRRtire rolling resistance.
UFutility factor.
ureaurea.
vehvehicle.
wwind.
wawind average.
yawyaw angle.
ysyaw sweep.
zerozero quantity.

(e)Other acronyms and abbreviations. This part uses the following additional abbreviations and acronyms:

Table 5 to Paragraph (e) of § 1037.805 -Other Acronyms and Abbreviations

Acronym Meaning
ABTaveraging, banking, and trading.
AECDauxiliary emission control device.
AESautomatic engine shutdown.
APUauxiliary power unit.
CDcharge-depleting.
CFDcomputational fluid dynamics.
CFRCode of Federal Regulations.
CITTcurb idle transmission torque.
CScharge-sustaining.
DOTDepartment of Transportation.
EPAEnvironmental Protection Agency.
FELFamily Emission Limit.
GAWRgross axle weight rating.
GCWRgross combination weight rating.
GEMgreenhouse gas emission model.
GVWRgross vehicle weight rating.
Heavy HDEheavy heavy-duty engine (see 40 CFR 1036.140 ).
Heavy HDVheavy heavy-duty vehicle (see § 1037.140 ).
HVACheating, ventilating, and air conditioning.
ISOInternational Organization for Standardization.
Light HDElight heavy-duty engine (see 40 CFR 1036.140 ).
Light HDVlight heavy-duty vehicle (see § 1037.140 ).
Medium HDEmedium heavy-duty engine (see 40 CFR 1036.140 ).
Medium HDVmedium heavy-duty vehicle (see § 1037.140 ).
NARANational Archives and Records Administration.
NHTSANational Highway Transportation Safety Administration.
PTOpower take-off.
RESSrechargeable energy storage system.
SAESAE International.
SEEstandard error of the estimate.
SKUstock-keeping unit.
Spark-ignition HDEspark-ignition heavy-duty engine (see 40 CFR 1036.140 ).
TRPMtire revolutions per mile.
TRRLtire rolling resistance level.
U.S.CUnited States Code.
VSLvehicle speed limiter.

(f)Constants. This part uses the following constants:

Table 6 to Paragraph (f) of § 1037.805 -Constants

Symbol Quantity Value
ggravitational constant9.80665 m·-2.
Rspecific gas constant287.058 J/(kg·K).

(g)Prefixes. This part uses the following prefixes to define a quantity:

Table 7 to Paragraph (g) of § 1037.805 -Prefixes

Symbol Quantity Value
[MICRO]micro10-6
mmilli10-3
ccenti10-2
kkilo103
Mmega106

40 C.F.R. §1037.805

81 FR 74048 , Oct. 25, 2016, as amended at 86 FR 34492 , June 29, 2021; 87 FR 64864 , Oct. 26, 2022; 88 FR 4654 , Jan. 24, 2023; 89 FR 29790 , Apr. 22, 2024
81 FR 74048, 10/25/2016, as amended at 86 FR 34492, 6/29/2021; 87 FR 64864, 10/26/2022; 88 FR 4654, 3/27/2023; 89 FR 29792, 6/24/2024