C. Terms and Definitions
Term / ISO / ECE (1958 Agreement) / ECE (1998 Agreement) / Japan / India /
aerodynamic drag / resistance of the air to the motion of a vehicle
aerodynamic stagnation point / point on the surface of a vehicle where the wind velocity is equal to zero
chassis dynamometer of coefficient control / chassis dynamometer of which absorption characteristics are determined by giving coefficients of a road-load approximation polynomial
chassis dynamometer of polygonal control / chassis dynamometer of which absorption characteristics are determined by giving load values at several speed points
chassis-dynamometer setting load / load to be set on the power-absorption unit of the chassis dynamometer
delay time / 
means the difference in time between the change of the component to be
measured at the reference point and a system response of 10 per cent of the final reading (t10) with the sampling probe being defined as the reference point. For the gaseous components, this is the transport time of the measured component from the sampling probe to the detector. / not defined
full flow dilution method / 
means the process of mixing the total exhaust flow with dilution air prior to separating a fraction of the diluted exhaust stream for analysis. / The whole exhaust emission emitted from the test vehicle shall be introduced into the CVS system or the dilution tunnel system, after sampling the diluted exhaust gas and dilution air into separate sampling bags of CVS system.
onboard anemometry / measurement of wind speed and direction with an anemometer appropriately installed to the test vehicle
partial flow dilution method / 
means the process of separating a part from the total exhaust flow, then mixing it with an appropriate amount of dilution air prior to the particulate sampling filter. / not defined
reference atmospheric conditions / atmospheric conditions of the following values, to which the road-load measurement results are corrected:
a)  atmospheric pressure: p0 = 100 kPa, unless otherwise specified by regulations;
b)  atmospheric temperature: t0 = 293 K, unless otherwise specified by regulations;
c)  dry air density: ρ0 = 1,189 kg/m3, unless otherwise specified by regulations;
d)  wind speed: 0 m/s.
reference speed / a vehicle speed at which a chassis-dynamometer load is verified. Reference speeds may be continuous speed points covering the complete speed range.
response time / 
means the difference in time between the change of the component to be measured at the reference point and a system response of 90 per cent of the final reading (t90) with the sampling probe being defined as the reference point, whereby the change of the measured component is at least 60 per cent full scale (FS) and takes place in less than 0.1 second. The system response time consists of the delay time to the system and of the rise time of the system. / not defined
rise time / 
means the difference in time the 10 per cent and 90 per cent response of the final reading (t90 – t10). / not defined
road load / general meaning of the force or torque which opposes the movement of a vehicle, including total resistance and/or running resistance
rolling resistance / opposing force in the drive-train, axles and tyres to the motion of a vehicle
running resistance / torque-resisting movement of a vehicle, measured by the torque-meter installed in the drive-train of a vehicle, including the friction torque in the drive-train downstream of the torque-meter
simulated road load / road load to be calculated from measured coastdown data using the least-square regression. See Annex 1 for the calculation procedure.
speed range / range of speed of chassis-dynamometer roller between 15 km/h and maximum reference speed plus 10 km/h, over which the coastdown test is conducted
stationary anemometry / measurement of wind speed and direction with an anemometer at a location and height above road level alongside the test road where the most representative wind conditions will be experienced
target road load / road load to be reproduced on the chassis dynamometer
total resistance / total force-resisting movement of a vehicle, measured either by the coastdown method or by the wind-tunnel/ chassis-dynamometer method, including the friction forces in the drive-train
transformation time / 
means the difference in time between the change of the component to be measured at the reference point and a system response of 50 per cent of the final reading (t50) with the sampling probe being defined as the reference point. The transformation time is used for the signal alignment of different measurement instruments. / not defined
Type I test / means the driving cycle (Parts One and Two) used for emission approvals, as detailed in Annex 4, Appendix 1. / not defined / Verifying the average tailpipe emissions
wind correction / correction of the effect of wind on road load, which is achieved either by stationary or by onboard anemometry