WLTP-10-18e
Road Load Family, GTR draft proposal
v3, 23.03.2015: Added EV criteria as a reference to interpolation family, improvements and
clarifications
v5, 30.03.2015: Text improvements for new paragraph 4.2.1.1.
v6, 07.04.2015: Includes proposals and input of Iddo.
5.7.
Road load family
Unless vehicles are identical with respect to the following characteristics, they shall not be
considered to be part of the same road load family:
(a) Transmission type (e.g. manual, automatic, CVT) and transmission model (e.g. torque
rating, number of gears, number of clutches, etc.);
(b) n/v ratios (engine rotational speed divided by vehicle speed). This requirement shall be
considered fulfilled if, for all transmission ratios concerned, the difference with respect to the
transmission ratios of the most commonly installed transmission type is within 25 per cent;
(c) Number of powered axles;
(d) An interpolation family shall be within one road load family;
(e) If at least one "electric machine" is coupled in the gearbox position "neutral" and the
vehicle is not equipped with a coast down mode (paragraph 4.2.1.5.5. of Annex 4) such, that
the electric machine has no influence on the road load, the criteria from 5.6. (f) shall apply.
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Annex 4
4.2.1.1. Application of the road load family
At the request of the manufacturer and by fulfilling the criteria of paragraph 5.7 of this GTR,
the road load values for the vehicles H and L of an interpolation family are calculated.
HR shall be the vehicle H of a road load family, described in 4.2.1. by replacing all references
to vehicle H by vehicle HR and interpolation family by road load family;
LR shall be the vehicle L of a road load family, described in 4.2.1. by replacing all references
to vehicle L by vehicle LR and interpolation family by road load family;
Instead of the requirements referring to the range of an interpolation family (paragraphs
1.2.3.1. and 1.2.3.2. of Annex 6), the cycle energy demand between HR and LR of the road
load family shall be at least 4% and shall not exceed 35% based on HR over a full WLTC
class 3 cycle.
The road load of HR (respectively LR) is determined according to this Annex.
The road load of vehicles H (and L) of an interpolation family within the road load family is
then calculated according to the paragraphs 3.2.3.2.2.- 3.2.3.2.2.4. of Annex 7, by:
(a) using HR and HL of the road load family instead of H and L as inputs for the equations;
(b) using the road load parameters (i.e. test mass, delta of aerodynamic drag compared to
vehicle LR and tyre rolling resistance) of the vehicle H (or L) of the interpolation family as
inputs for the "individual vehicle";
(c) repeating this calculation for each H and L vehicle of every interpolation family within the
road load family.
The road load interpolation shall only be applied on those road load relevant characteristics
that were chosen to be different between test vehicle LR and HR; for the other road load
relevant characteristic(s) the value of vehicle HR shall apply.