ANNEX B4

Road load and dynamometer setting

1. Scope

This annex describes the determination of the road load of a test vehicle and the transfer of that road load to a chassis dynamometer.

2. Terms and definitions

2.1. For the purpose of this document, the terms and definitions given in paragraph 3. of this Regulation shall have primacy. Where definitions are not provided in paragraph 3. of this Regulation, definitions given in ISO 3833:1977 "Road vehicles – Types – Terms and definitions" shall apply.

2.2. Reference speed points shall start at 20 km/h in incremental steps of 10 km/h and with the highest reference speed according to the following provisions:

(a) The highest reference speed point shall be 130 km/h or the reference speed point immediately above the maximum speed of the applicable test cycle if this value is less than 130 km/h. In the case that the applicable test cycle contains less than the 4 cycle phases (Low, Medium, High and Extra High) and at the request of the manufacturer and with approval of the responsible authority, the highest reference speed may be increased to the reference speed point immediately above the maximum speed of the next higher phase, but no higher than 130 km/h; in this case road load determination and chassis dynamometer setting shall be done with the same reference speed points;

(b) If a reference speed point applicable for the cycle plus 14 km/h is more than or equal to the maximum vehicle speed vmax, this reference speed point shall be excluded from the coastdown test and from chassis dynamometer setting. The next lower reference speed point shall become the highest reference speed point for the vehicle.

2.3. Unless otherwise specified, a cycle energy demand shall be calculated according to paragraph 5. of Annex B7 over the target speed trace of the applicable drive cycle.

2.4. f0, f1, f2 are the road load coefficients of the road load equation F = f0 + f1 × v + f2 × v2 determined according to this annex.

f0 is the constant road load coefficient and shall be rounded according to paragraph 6.1.8. of this Regulation to one place of decimal, N; f1 is the first order road load coefficient and shall be rounded according to paragraph 6.1.8. of this Regulation to three places of decimal, N/(km/h); f2 is the second order road load coefficient and shall be rounded according to paragraph 6.1.8. of this Regulation to five places of decimal, N/(km/h)2.

Unless otherwise stated, the road load coefficients shall be calculated with a least square regression analysis over the range of the reference speed points.

2.5. Rotational mass

2.5.1. Determination of mr

mr is the equivalent effective mass of all the wheels and vehicle components rotating with the wheels on the road while the gearbox is placed in neutral, in kilograms (kg). mr shall be measured or calculated using an appropriate technique agreed upon by the responsible authority. Alternatively, mr may be estimated to be 3 per cent of the sum of the mass in running order and 25 kg.

2.5.2. Application of rotational mass to the road load

Coastdown times shall be transferred to forces and vice versa by taking into account the applicable test mass plus mr. This shall apply to measurements on the road as well as on a chassis dynamometer.

2.5.3. Application of rotational mass for the inertia setting

If the vehicle is tested on a dynamometer in 4WD operation, the equivalent inertia mass of the chassis dynamometer shall be set to the applicable test mass.'

Otherwise, the equivalent inertia mass of the chassis dynamometer shall be set to the test mass plus either the equivalent effective mass of the wheels not influencing the measurement results or 50 per cent of mr.

2.6. Additional masses for setting the test mass shall be applied such that the weight distribution of that vehicle is approximately the same as that of the vehicle with its mass in running order. In the case of Category N vehicles or passenger vehicles derived from Category N vehicles, the additional masses shall be located in a representative manner and shall be justified to the responsible authority upon their request. The weight distribution of the vehicle shall be recorded and shall be used for any subsequent road load determination testing.

3. General requirements

The manufacturer shall be responsible for the accuracy of the road load coefficients and shall ensure this for each production vehicle within the road load family. Tolerances within the road load determination, simulation and calculation methods shall not be used to underestimate the road load of production vehicles. At the request of the responsible authority, the accuracy of the road load coefficients of an individual vehicle shall be demonstrated.

3.1. Overall measurement accuracy, precision, resolution and frequency

The required overall measurement accuracy shall be as follows:

(a) Vehicle speed accuracy: ±0.2 km/h with a measurement frequency of at least 10 Hz;

(b) Time: min. accuracy: ±10 ms; min. precision and resolution: 10 ms;

(c) Wheel torque accuracy: ±6 Nm or ±0.5 per cent of the maximum measured total torque, whichever is greater, for the whole vehicle, with a measurement frequency of at least 10 Hz;

(d) Wind speed accuracy: ±0.3 m/s, with a measurement frequency of at least 1 Hz;

(e) Wind direction accuracy: ±3°, with a measurement frequency of at least 1 Hz;

(f) Atmospheric temperature accuracy: ±1 °C, with a measurement frequency of at least 0.1 Hz;

(g) Atmospheric pressure accuracy: ±0.3 kPa, with a measurement frequency of at least 0.1 Hz;

(h) Vehicle mass accuracy measured on the same weighing scale before and after the test: ±10 kg (±20 kg for vehicles > 4,000 kg);

(i) Tyre pressure accuracy: ±5 kPa;

(j) Wheel rotational speed accuracy: ±0.05 s-1 or 1 per cent, whichever is greater.

3.2. Wind tunnel criteria

3.2.1. Wind velocity

The wind velocity during a measurement shall remain within ±2 km/h at the centre of the test section. The possible wind velocity shall be at least 140 km/h.

3.2.2. Air temperature

The air temperature during a measurement shall remain within ±3 °C at the centre of the test section. The air temperature distribution at the nozzle outlet shall remain within ±3 °C.

3.2.3. Turbulence

For an equally-spaced 3 by 3 grid over the entire nozzle outlet, the turbulence intensity, Tu, shall not exceed 1 per cent. See Figure A4/1.

Figure A4/1

Turbulence intensity

where:

Tu is the turbulence intensity; u' is the turbulent velocity fluctuation, m/s; U∞ is the free flow velocity, m/s.

3.2.4. Solid blockage ratio

The vehicle blockage ratio εsb expressed as the quotient of the vehicle frontal area and the area of the nozzle outlet as calculated using the following equation, shall not exceed 0.35.

where:

εsb is the vehicle blockage ratio; Af is the frontal area of the vehicle, m2; Anozzle is the nozzle outlet area, m2.

3.2.5. Rotating wheels

To properly determine the aerodynamic influence of the wheels, the wheels of the test vehicle shall rotate at such a speed that the resulting vehicle velocity is within ±3 km/h of the wind velocity.

3.2.6. Moving belt

To simulate the fluid flow at the underbody of the test vehicle, the wind tunnel shall have a moving belt extending from the front to the rear of the vehicle. The speed of the moving belt shall be within ±3 km/h of the wind velocity.

3.2.7. Fluid flow angle

At nine equally distributed points over the nozzle area, the root mean square deviation of both the pitch angle α and the yaw angle β (Y-, Z-plane) at the nozzle outlet shall not exceed 1°.

3.2.8. Air pressure

At nine equally distributed points over the nozzle outlet area, the standard deviation of the total pressure at the nozzle outlet shall be less than or equal to 0.02.

where:

σ is the standard deviation of the pressure ratio ; ΔPt is the variation of total pressure between the measurement points, N/m2; q is the dynamic pressure, N/ m2.

The absolute difference of the pressure coefficient cp over a distance 3 metres ahead and 3 metres behind the centre of the balance in the empty test section and at a height of the centre of the nozzle outlet shall not deviate more than ± 0.02.

where:

cp is the pressure coefficient.

3.2.9. Boundary layer thickness

At x = 0 (balance center point), the wind velocity shall have at least 99 per cent of the inflow velocity 30 mm above the wind tunnel floor.

δ99(x = 0 m) ≤ 30 mm

where:

δ99 is the distance perpendicular to the road where 99 per cent of free stream velocity is reached (boundary layer thickness).

3.2.10. Restraint blockage ratio

The restraint system mounting shall not be in front of the vehicle. The relative blockage ratio of the vehicle frontal area due to the restraint system, εrestr, shall not exceed 0.10.

where:

εrestr is the relative blockage ratio of the restraint system; Arestr is the frontal area of the restraint system projected on the nozzle face, m2; Af is the frontal area of the vehicle, m2.

3.2.11. Measurement accuracy of the balance in the x-direction

The inaccuracy of the resulting force in the x-direction shall not exceed ± 5 N. The resolution of the measured force shall be within ± 3 N.

3.2.12. Measurement precision

The precision of the measured force shall be within ± 3 N.

4. Road load measurement on road

4.1. Requirements for road test

4.1.1. Atmospheric conditions for road test

Atmospheric conditions (wind conditions, atmospheric temperature and atmospheric pressure) shall be measured according to paragraph 3.1. of this annex. Only those atmospheric conditions measured during coastdown time measurements and/or torque measurement shall be used for checking data validity and corrections.

4.1.1.1. Permissible wind conditions when using stationary anemometry and on-board anemometry

4.1.1.1.1. Permissible wind conditions when using stationary anemometry The wind speed shall be measured at a location and height above the road level alongside the test road where the most representative wind conditions will be experienced. In cases where tests in opposite directions cannot be performed at the same part of the test track (e.g. on an oval test track with an obligatory driving direction), the wind speed and direction shall be measured at the opposite parts of the test track. The wind conditions during run pairs shall meet all of the following criteria: (a) Wind speed shall be less than 5 m/s over a 5 second moving average period; (b) Peak wind speeds shall not exceed 8 m/s for more than 2 consecutive seconds; (c) The arithmetic average of the vector component of the wind speed across the test road shall be less than 2 m/s. The wind correction shall be calculated according to paragraph 4.5.3. of this annex.

4.1.1.1.2. Permissible wind conditions when using on-board anemometry For testing with an on-board anemometer, a device as described in paragraph 4.3.2. of this annex shall be used. The wind conditions during run pairs shall meet all of the following criteria: (a) The arithmetic average of the wind speed shall be less than 7 m/s; (b) Peak wind speeds shall not exceed 10 m/s for more than 2 consecutive seconds; (c) The arithmetic average of the vector component of the wind speed across the test road shall be less than 4 m/s.

4.1.1.2. Atmospheric temperature

The atmospheric temperature should be within the range of 5 °C up to and including 40 °C.

At the option of the manufacturer, coastdowns may be performed between 1 °C and 5 °C.

If the difference between the highest and the lowest measured temperature during the coastdown test is more than 5 °C, the temperature correction shall be applied separately for each run with the arithmetic average of the ambient temperature of that run.

In that case, the values of the road load coefficients f0, f1 and f2 shall be determined and corrected for each run pair. The final set of f0, f1 and f2 values shall be the arithmetic average of the individually corrected coefficients f0, f1 and f2 respectively.

4.1.2. Test road

The road surface shall be flat, even, clean, dry and free of obstacles or wind barriers that might impede the measurement of the road load, and its texture and composition shall be representative of current urban and highway road surfaces, i.e. no airstrip-specific surface. The longitudinal slope of the test road shall not exceed ± 1 per cent. The local slope between any points 3 metres apart shall not deviate more than ±0.5 per cent from this longitudinal slope. If tests in opposite directions cannot be performed at the same part of the test track (e.g. on an oval test track with an obligatory driving direction), the sum of the longitudinal slopes of the parallel test track segments shall be between 0 and an upward slope of 0.1 per cent. The maximum camber of the test road shall be 1.5 per cent.

4.2. Preparation

4.2.1. Test vehicle

Each test vehicle shall conform in all its components with the production series, (e.g. side mirrors shall be same position as during normal vehicle operation, body gaps shall not be sealed), or, if the vehicle is different from the production vehicle, a full description shall be recorded.

4.2.1.1. Requirements for test vehicle selection

4.2.1.1.1. Without using the interpolation method A test vehicle (vehicle H) with the combination of road load relevant characteristics (i.e. mass, aerodynamic drag and tyre rolling resistance) producing the highest cycle energy demand shall be selected from the family (see paragraphs 6.3.2. and 6.3.3. of this Regulation). If the aerodynamic influence of the different wheels within one interpolation family is not known, the selection shall be based on the highest expected aerodynamic drag. As a guideline, the highest aerodynamic drag may be expected for wheels with (a) the largest width, (b) the largest diameter, and (c) the most open structure design (in that order of importance). The wheel selection shall be performed additional to the requirement of the highest cycle energy demand.

4.2.1.1.2. Using an interpolation method At the request of the manufacturer, an interpolation method may be applied. In this case, two test vehicles shall be selected from the family complying with the respective family requirement. Test vehicle H shall be the vehicle producing the higher, and preferably highest, cycle energy demand of that selection, test vehicle L the one producing the lower, and preferably lowest, cycle energy demand of that selection. All items of optional equipment and/or body shapes that are chosen not to be considered when applying the interpolation method shall be identical for both test vehicles H and L such that these items of optional equipment produce the highest combination of the cycle energy demand due to their road load relevant characteristics (i.e. mass, aerodynamic drag and tyre rolling resistance). In the case where individual vehicles can be supplied with a complete set of standard wheels and tyres and in addition a complete set of snow tyres (marked with 3 Peaked Mountain and Snowflake – 3PMS) with or without wheels, the additional wheels/tyres shall not be considered as optional equipment.

4.2.1.1.2.1. The following requirements between vehicles H and L shall be fulfilled for the road load relevant characteristics: (a) To allow extrapolating road load coefficients: (i) If f0_ind is below f*0_L or above f0_H as defined in paragraph 3.2.3.2.2.4. of Annex B7 while performing the calculation in paragraph 3.2.3.2.2.4. of Annex B7, the following minimum differences between H and L are required: Rolling resistance of at least 1.0 kg/tonne and a mass of at least 30 kg; in case of RR between 0 and 1.0, the minimum of the mass difference is replaced with 100 kg instead of 30 kg; (ii) If f2_ind is below f*2_L or above f2_H as defined in paragraph 3.2.3.2.2.4. of Annex B7 while performing the calculation in paragraph 3.2.3.2.2.4. of Annex B7, the following minimum difference between H and L is required: Aerodynamic drag (CD × Af) of at least 0.05 m2. If the manufacturer can demonstrate that the results after an extrapolation are still rational, the minimum criteria in points (i) to (iii) above can be waived. (b) For each road load characteristic (i.e. mass, aerodynamic drag and tyre rolling resistance) as well as for the road load coefficients f0 and f2, the value of vehicle H shall be higher than that of vehicle L, otherwise the worst case shall be applied for that road load relevant characteristic. At the request of the manufacturer and upon approval by the responsible authority the requirements of this point can be waived.

4.2.1.1.2.2. To achieve a sufficient difference between vehicle H and vehicle L on a particular road load relevant characteristic, or in order to fulfil criteria of paragraph 4.2.1.1.2.1. of this annex, the manufacturer may artificially worsen vehicle H, e.g. by applying a higher test mass.

4.2.1.2. Requirements for families

4.2.1.2.1. Requirements for applying the interpolation family without using the interpolation method For the criteria defining an interpolation family, see paragraph 6.3.2. of this Regulation.

4.2.1.2.2. Requirements for applying the interpolation family using the interpolation method are: (a) Fulfilling the interpolation family criteria listed in paragraph 6.3.2. of this Regulation; (b) Fulfilling the requirements in paragraphs 2.3.1. and 2.3.2. of Annex B6; (c) Performing the calculations in paragraph 3.2.3.2. of Annex B7.

4.2.1.2.3. Requirements for applying the road load family

4.2.1.2.3.1. At the request of the manufacturer and upon fulfilling the criteria of paragraph 6.3.3. of this Regulation, the road load values for vehicles H and L of an interpolation family shall be calculated.

4.2.1.2.3.2. Test vehicles H and L as defined in paragraph 4.2.1.1.2. of this annex shall be referred to as H R and L R for the purpose of the road load family.

4.2.1.2.3.3. The difference in cycle energy demand between H R and L R of the road load family shall be at least 4 per cent and shall not exceed 35 per cent based on H R over a complete WLTC Class 3 cycle. If more than one transmission is included in the road load family, a transmission with the highest power losses shall be used for road load determination.

4.2.1.2.3.4. If the road load delta of the vehicle option causing the friction difference is determined according to paragraph 6.8. of this annex, a new road load family shall be calculated which includes the road load delta in both vehicle L and vehicle H of that new road load family. f0,N = f0,R + f0,Delta f1,N = f1,R + f1,Delta f2,N = f2,R + f2,Delta where: N refers to the road load coefficients of the new road load family; R refers to the road load coefficients of the reference road load family; Delta refers to the delta road load coefficients determined in paragraph 6.8.1. of this annex.

4.2.1.3. Allowable combinations of test vehicle selection and family requirements

Table A4/1 shows the permissible combinations of test vehicle selection and family requirements as described in paragraphs 4.2.1.1. and 4.2.1.2. of this annex.

Table A4/1

Permissible combinations of test vehicle selection and family requirements

Requirements to be fulfilled: (1) w/o interpolation method (2) Interpolation method w/o road load family (3) Applying the road load family (4) Interpolation method using one or more road load families Road load test vehicle Paragraph 4.2.1.1.1. of this annex. Paragraph 4.2.1.1.2. of this annex. Paragraph 4.2.1.1.2. of this annex. n.a. Family Paragraph 4.2.1.2.1. of this annex. Paragraph 4.2.1.2.2. of this annex. Paragraph 4.2.1.2.3. of this annex. Paragraph 4.2.1.2.2. of this annex. Additional none none none Application of column (3) "Applying the road load family" and application of paragraph 4.2.1.3.1. of this annex.

4.2.1.3.1. Deriving road loads of an interpolation family from a road load family Road loads HR and/or LR shall be determined according to this annex. The road load of vehicle H (and L) of an interpolation family within the road load family shall be calculated according to paragraphs 3.2.3.2.2. to 3.2.3.2.2.4. inclusive of Annex B7 by: (a) Using HR and LR 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, Δ(CD ×Af) compared to vehicle LR, and tyre rolling resistance) of 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 identified to be different between test vehicle LR and HR. For other road load-relevant characteristic(s), the value of vehicle HR shall apply. H and L of the interpolation family may be derived from different road load families. If that difference between these road load families comes from applying the delta method, refer to paragraph 4.2.1.2.3.4. of this annex.

4.2.1.4. Application of the road load matrix family

A vehicle that fulfils the criteria of paragraph 6.3.4. of this Regulation that is:

(a) Representative of the intended series of complete vehicles to be covered by the road load matrix family in terms of estimated worst CD value and body shape; and

(b) Representative of the intended series of vehicles to be covered by the road load matrix family in terms of estimated average of the mass of optional equipment shall be used to determine the road load.

In the case that no representative body shape for a complete vehicle can be determined, the test vehicle shall be equipped with a square box with rounded corners with radii of maximum of 25 mm and a width equal to the maximum width of the vehicles covered by the road load matrix family, and a total height of the test vehicle of 3.0 m ±0.1 m, including the box.

The manufacturer and the responsible authority shall agree which vehicle test model is representative.

The values of the vehicle parameters test mass, tyre rolling resistance and frontal area of both a vehicle HM and LM shall be determined in such a way that vehicle HM produces the highest cycle energy demand and vehicle LM the lowest cycle energy from the road load matrix family. The manufacturer and the responsible authority shall agree on the vehicle parameters for vehicles HM and LM.

The road load of all individual vehicles of the road load matrix family, including HM and LM, shall be calculated according to paragraph 5.1. of this annex.

4.2.1.5. Movable aerodynamic body parts

Movable aerodynamic body parts on the test vehicles shall operate during road load determination as intended under WLTP Type 1 test conditions (test temperature, vehicle speed and acceleration range, engine load, etc.).

Every vehicle system that dynamically modifies the vehicle’s aerodynamic drag (e.g. vehicle height control) shall be considered to be a movable aerodynamic body part. Appropriate requirements shall be added if future vehicles are equipped with movable aerodynamic items of optional equipment whose influence on aerodynamic drag justifies the need for further requirements.

4.2.1.6. Weighing

Before and after the road load determination procedure, the selected vehicle shall be weighed, including the test driver and equipment, to determine the arithmetic average mass mav. The mass of the vehicle shall be greater than or equal to the test mass of vehicle H or of vehicle L at the start of the road load determination procedure.

4.2.1.7. Test vehicle configuration

The test vehicle configuration shall be recorded and shall be used for any subsequent coastdown testing.

4.2.1.8. Test vehicle condition

4.2.1.8.1. Run-in The test vehicle shall be suitably run-in for the purpose of the subsequent test for at least 10,000 but no more than 80,000 km. At the request of the manufacturer, a vehicle with a minimum of 3,000 km may be used.

4.2.1.8.2. Manufacturer's specifications The vehicle shall conform to the manufacturer’s intended production vehicle specifications regarding tyre pressures described in paragraph 4.2.2.3. of this annex, wheel alignment described in paragraph 4.2.1.8.3. of this annex, ground clearance, vehicle height, drivetrain and wheel bearing lubricants, and brake adjustment to avoid unrepresentative parasitic drag.

4.2.1.8.3. Wheel alignment Toe and camber shall be set to the maximum deviation from the longitudinal axis of the vehicle in the range defined by the manufacturer. If a manufacturer prescribes values for toe and camber for the vehicle, these values shall be used. At the request of the manufacturer, values with higher deviations from the longitudinal axis of the vehicle than the prescribed values may be used. The prescribed values shall be the reference for all maintenance during the lifetime of the vehicle. Other adjustable wheel alignment parameters (such as caster) shall be set to the values recommended by the manufacturer. In the absence of recommended values, they shall be set to the arithmetic average of the range defined by the manufacturer. Such adjustable parameters and set values shall be recorded.

4.2.1.8.4. Closed panels During the road load determination, the engine compartment cover, luggage compartment cover, manually-operated movable panels and all windows shall be closed.

4.2.1.8.5. Vehicle coastdown mode If the determination of dynamometer settings cannot meet the criteria described in paragraphs 8.1.3. or 8.2.3. of this annex due to non-reproducible forces, the vehicle shall be equipped with a vehicle coastdown mode. The vehicle coastdown mode shall be approved and its use shall be recorded by the responsible authority. If a vehicle is equipped with a vehicle coastdown mode, it shall be engaged both during road load determination and on the chassis dynamometer.

4.2.2. Tyres

4.2.2.1. Tyre rolling resistance

Tyre rolling resistances shall be measured according to Annex 6 to the 02 series of amendments to UN Regulation No. 117, or an internationally-accepted equivalent. The rolling resistance coefficients shall be aligned according to the respective regional procedures (e.g. EU 1235/2011), and categorised according to the rolling resistance classes in Table A4/2.

Table A4/2

Energy efficiency classes according to rolling resistance coefficients (RRC) for C1, C2 and C3 tyres and the RRC values to be used for those energy efficiency classes in the interpolation, kg/tonne

Energy efficiency class Range of RRC for C1 tyres Range of RRC for C2 tyres Range of RRC for C3 tyres 1 RRC ≤ 6.5 RRC ≤ 5.5 RRC ≤ 4.0 2 6.5 < RRC ≤ 7.7 5.5 < RRC ≤ 6.7 4.0 < RRC ≤ 5.0 3 7.7 < RRC ≤ 9.0 6.7 < RRC ≤ 8.0 5.0 < RRC ≤ 6.0 4 9.0 < RRC ≤ 10.5 8.0 < RRC ≤ 9.2 6.0 < RRC ≤ 7.0 5 10.5 < RRC ≤ 12.0 9.2 < RRC ≤ 10.5 7.0 < RRC ≤ 8.0 6 RRC > 12.0 RRC > 10.5 RRC > 8.0 Energy efficiency class Value of RRC to be used for interpolation for C1 tyres Value of RRC to be used for interpolation for C2 tyres Value of RRC to be used for interpolation for C3 tyres 1 RRC = 5.9 (*1) RRC = 4.9 (*1) RRC = 3.5 (*1) 2 RRC = 7.1 RRC = 6.1 RRC = 4.5 3 RRC = 8.4 RRC = 7.4 RRC = 5.5 4 RRC = 9.8 RRC = 8.6 RRC = 6.5 5 RRC = 11.3 RRC = 9.9 RRC = 7.5 6 RRC = 12.9 RRC = 11.2 RRC = 8.5

If the interpolation method is applied to rolling resistance, the actual rolling resistance values for the tyres fitted to the test vehicles L and H shall be used as input for the interpolation method. For an individual vehicle within an interpolation family, the RRC value for the energy efficiency class of the tyres fitted shall be used.

In the case where individual vehicles can be supplied with a complete set of standard wheels and tyres and in addition a complete set of snow tyres (marked with 3 Peaked Mountain and Snowflake – 3PMS) with or without wheels, the additional wheels/tyres shall not be considered as optional equipment.

4.2.2.2. Tyre condition

Tyres used for the test shall:

(a) Not be older than 2 years after the production date;

(b) Not be specially conditioned or treated (e.g. heated or artificially aged), with the exception of grinding in the original shape of the tread;

(c) Be run-in on a road for at least 200 km before road load determination;

(d) Have a constant tread depth before the test between 100 and 80 per cent of the original tread depth at any point over the full tread width of the tyre.

After measurement of tread depth, the driving distance shall be limited to 500 km. If 500 km are exceeded, the tread depth shall be measured again.

4.2.2.3. Tyre pressure

The front and rear tyres shall be inflated to the lower limit of the tyre pressure range for the respective axle for the selected tyre at the coastdown test mass, as specified by the vehicle manufacturer.

4.2.2.3.1. Tyre pressure adjustment If the difference between ambient and soak temperature is more than 5 °C, the tyre pressure shall be adjusted as follows: (a) The tyres shall be soaked for more than 1 hour at 10 per cent above the target pressure; (b) Prior to testing, the tyre pressure shall be reduced to the inflation pressure as specified in paragraph 4.2.2.3. of this annex, adjusted for difference between the soaking environment temperature and the ambient test temperature at a rate of 0.8 kPa per 1 °C using the following equation: Δpt = 0.8 × (Tsoak – Tamb) where: Δpt is the tyre pressure adjustment added to the tyre pressure defined in paragraph 4.2.2.3. of this annex, kPa; 0.8 is the pressure adjustment factor, kPa/°C; Tsoak is the tyre soaking temperature, °C; Tamb is the test ambient temperature, °C. (c) Between the pressure adjustment and the vehicle warm-up, the tyres shall be shielded from external heat sources including sun radiation.

4.2.3. Instrumentation

Any instruments shall be installed in such a manner as to minimise their effects on the aerodynamic characteristics of the vehicle.

If the effect of the installed instrument on (CD × Af) is expected to be greater than 0.015 m2, the difference in the value of (CD × Af) of the vehicle with and without the instrument shall be measured in a wind tunnel fulfilling the criteria in paragraph 3.2. of this annex. The corresponding difference shall be subtracted from f2. At the request of the manufacturer, and with approval of the responsible authority, the determined value may be used for similar vehicles where the influence of the equipment is expected to be the same.

4.2.4. Vehicle warm-up

4.2.4.1. On the road

Warming up shall only be performed by driving the vehicle.

4.2.4.1.1. Before warm-up, the vehicle shall be decelerated with the clutch disengaged or an automatic transmission placed in neutral by moderate braking from 80 to 20 km/h within 5 to 10 seconds. After this braking, there shall be no further actuation or manual adjustment of the braking system. At the request of the manufacturer and upon approval of the responsible authority, the brakes may also be activated after the warm-up with the same deceleration as described in this paragraph and only if necessary.

4.2.4.1.2. Warming up and stabilization All vehicles shall be driven at 90 per cent of the maximum speed of the applicable WLTC. The vehicle may be driven at 90 per cent of the maximum speed of the next higher phase (see Table A4/3) if this phase is added to the applicable WLTC warm-up procedure as defined in paragraph 7.3.4. of this annex. The vehicle shall be warmed up for at least 20 minutes until stable conditions are reached. Table A4/3 Warming-up and stabilization across phases (as applicable) Cycle class Applicable WLTC 90 per cent of maximum speed Next higher phase Class 1 Low1 + Medium1 58 km/h NA Class 2 Low2 + Medium2 + High2 + Extra High2 111 km/h NA Low2 + Medium2 + High2 77 km/h Extra High (111 km/h) Class 3 Low3 + Medium3 + High3 + Extra High3 118 km/h NA Low3 + Medium3 + High3 88 km/h Extra High (118 km/h)

4.2.4.1.3. Criterion for stable condition Refer to paragraph 4.3.1.4.2. of this annex.

4.3. Measurement and calculation of road load using the coastdown method

The road load shall be determined by using either the stationary anemometry (paragraph 4.3.1. of this annex) or the on-board anemometry (paragraph 4.3.2. of this annex) method.

4.3.1. Coastdown method using stationary anemometry

4.3.1.1. Selection of reference speeds for road load curve determination

Reference speeds for road load determination shall be selected according to paragraph 2.2. of this annex.

4.3.1.2. Data collection

During the test, elapsed time and vehicle speed shall be measured at a minimum frequency of 10 Hz.

4.3.1.3. Vehicle coastdown procedure

4.3.1.3.1. Following the vehicle warm-up procedure described in paragraph 4.2.4. of this annex and immediately prior to each coastdown run, the vehicle shall be accelerated to 10 to 15 km/h above the highest reference speed and shall be driven at that speed for a maximum of 1 minute. After that, the coastdown run shall be started immediately.

4.3.1.3.2. During a coastdown run, the transmission shall be in neutral. Any movement of the steering wheel shall be avoided as much as possible, and the vehicle brakes shall not be operated.

4.3.1.3.3. The test shall be repeated until the coastdown data satisfy the statistical precision requirements as specified in paragraph 4.3.1.4.2. of this annex.

4.3.1.3.4. Although it is recommended that each coastdown run should be performed without interruption, if data cannot be collected in a single run for all the reference speed points, the coastdown test may be performed with coastdown runs where the first and last reference speeds are not necessarily the highest and lowest reference speeds. In this case, the following additional requirements shall apply: (a) At least one reference speed in each coastdown run shall overlap with the immediately higher speed range coastdown run. This reference speed shall be referred to as a split point; (b) At each overlapped reference speed, the average force of the immediately lower speed coastdown run shall not deviate from the average force of the immediately higher speed coastdown run by ±10 N or ± 5 per cent, whichever is greater; (c) Overlapped reference speed data of the lower speed coastdown run shall be used only for checking criterion (b) and shall be excluded from evaluation of the statistical precision as defined in paragraph 4.3.1.4.2. of this annex; (d) The overlapped speed may be less than 10 km/h but shall not be less than 5 km/h. In this case, overlap criterion (b) shall be checked by either extrapolating the polynomial curves for the lower and higher speed segment to a 10 km/h overlap, or by comparing the average force in the specific speed range.

4.3.1.3.5. It is recommended that coastdown runs should be conducted successively without undue delay between runs. If there is a delay between runs (e.g. for a driver break, checking vehicle integrity, etc.), the vehicle shall be warmed up again as described in paragraph 4.2.4. and the coastdown runs shall be re-commenced from this point.

4.3.1.4. Coastdown time measurement

4.3.1.4.1. The coastdown time corresponding to reference speed v j as the elapsed time from vehicle speed (v j + 5 km/h) to (v j – 5 km/h) shall be measured.

4.3.1.4.2. These measurements shall be carried out in opposite directions until a minimum of three pairs of measurements have been obtained that satisfy the statistical precision p j defined in the following equation: where: pj is the statistical precision of the measurements made at reference speed vj; n is the number of pairs of measurements; Δtpj is the harmonic average of the coastdown time at reference speed vj in seconds given by the following equation: where: Δtji is the harmonic average coastdown time of the ith pair of measurements at velocity vj, seconds, s, given by the following equation: where: Δtjai and Δtjbi are the coastdown times of the ith measurement at reference speed vj, in seconds, s, in the respective directions a and b; σj is the standard deviation, expressed in seconds, s, defined by: h is a coefficient given in Table A4/4. Table A4/4 Coefficient h as a function of n n h n h 3 4.3 17 2.1 4 3.2 18 2.1 5 2.8 19 2.1 6 2.6 20 2.1 7 2.5 21 2.1 8 2.4 22 2.1 9 2.3 23 2.1 10 2.3 24 2.1 11 2.2 25 2.1 12 2.2 26 2.1 13 2.2 27 2.1 14 2.2 28 2.1 15 2.2 29 2.0 16 2.1 30 2.0

4.3.1.4.3. If during a measurement in one direction any external factor or driver action occurs that obviously influences the road load test, that measurement and the corresponding measurement in the opposite direction shall be rejected. All the rejected data and the reason for rejection shall be recorded, and the number of rejected pairs of measurement shall not exceed 1/3 of the total number of measurement pairs. In the case of split runs, the rejection criteria shall be applied at each split run speed range. Due to uncertainty of data validity and for practical reasons, more than the minimum number of run pairs required in paragraph 4.3.1.4.2. of this annex may be performed, but the total number of run pairs shall not exceed 30 runs including the rejected pairs as described in this paragraph. In this case, data evaluation shall be carried out as described in paragraph 4.3.1.4.2. of this annex starting from the first run pair, then including as many consecutive run pairs as needed to reach the statistical precision on a data set containing no more than 1/3 of rejected pairs. The remaining run pairs shall be disregarded.

4.3.1.4.4. The following equation shall be used to compute the arithmetic average of the road load where the harmonic average of the alternate coastdown times shall be used: where: Δv is 5 km/h; Δtj is the harmonic average of alternate coastdown time measurements at velocity vj, seconds, s, given by: where: Δtja and Δtjb are the harmonic average coastdown times in directions a and b, respectively, corresponding to reference speed vj, in seconds, s, given by the following two equations: and: where: mav is the arithmetic average of the test vehicle masses at the beginning and end of road load determination, kg; mr is the equivalent effective mass of rotating components according to paragraph 2.5.1. of this annex; The coefficients, f0, f1 and f2 in the road load equation shall be calculated with a least squares regression analysis. In the case that the tested vehicle is the representative vehicle of a road load matrix family, the coefficient f1 shall be set to zero and the coefficients f0 and f2 shall be recalculated with a least squares regression analysis.

4.3.1.4.5. Correction to reference conditions The curve determined in paragraph 4.3.1.4.4. of this annex shall be corrected to reference conditions as specified in paragraph 4.5. of this annex.

4.3.2. Coastdown method using on-board anemometry

The vehicle shall be warmed up and stabilised according to paragraph 4.2.4. of this annex.

4.3.2.1. Additional instrumentation for on-board anemometry

The on-board anemometer and instrumentation shall be calibrated by means of operation on the test vehicle where such calibration occurs during the warm-up for the test.

4.3.2.1.1. Relative wind speed shall be measured at a minimum frequency of 1 Hz and to an accuracy of 0.3 m/s. Vehicle blockage shall be accounted for in the calibration of the anemometer.

4.3.2.1.2. Wind direction shall be relative to the direction of the vehicle. The relative wind direction (yaw) shall be measured with a resolution of 1 degree and an accuracy of 3 degrees; the dead band of the instrument shall not exceed 10 degrees and shall be directed towards the rear of the vehicle.

4.3.2.1.3. Before the coastdown, the anemometer shall be calibrated for speed and yaw offset as specified in ISO 10521-1:2006(E) Annex A.

4.3.2.1.4. Anemometer blockage shall be corrected for in the calibration procedure as described in ISO 10521-1:2006(E) Annex A in order to minimise its effect.

4.3.2.2. Selection of vehicle speed range for road load curve determination

The test vehicle speed range shall be selected according to paragraph 2.2. of this annex.

4.3.2.3. Data collection

During the procedure, elapsed time, vehicle speed, and air velocity (speed, direction) relative to the vehicle, shall be measured at a minimum frequency of 5 Hz. Ambient temperature shall be synchronised and sampled at a minimum frequency of 0.1 Hz.

4.3.2.4. Vehicle coastdown procedure

The measurements shall be carried out in run pairs in opposite directions until a minimum of ten consecutive runs (five pairs) have been obtained. Should an individual run fail to satisfy the required on-board anemometry test conditions, that pair, i.e. that run and the corresponding run in the opposite direction, shall be rejected. All valid pairs shall be included in the final analysis with a minimum of 5 pairs of coastdown runs. See paragraph 4.3.2.6.10. of this annex for statistical validation criteria.

The anemometer shall be installed in a position such that the effect on the operating characteristics of the vehicle is minimised.

The anemometer shall be installed according to one of the options below:

(a) Using a boom approximately 2 metres in front of the vehicle’s forward aerodynamic stagnation point;

(b) On the roof of the vehicle at its centreline. If possible, the anemometer shall be mounted within 30 cm from the top of the windshield;

(c) On the engine compartment cover of the vehicle at its centreline, mounted at the midpoint position between the vehicle front and the base of the windshield.

In all cases, the anemometer shall be mounted parallel to the road surface. In the event that positions (b) or (c) are used, the coastdown results shall be analytically adjusted for the additional aerodynamic drag induced by the anemometer. The adjustment shall be made by testing the coastdown vehicle in a wind tunnel both with and without the anemometer installed in the same position as used on the track. The calculated difference shall be the incremental aerodynamic drag coefficient CD combined with the frontal area, which shall be used to correct the coastdown results.

4.3.2.4.1. Following the vehicle warm-up procedure described in paragraph 4.2.4. of this annex and immediately prior to each coastdown run, the vehicle shall be accelerated to 10 to 15 km/h above the highest reference speed and shall be driven at that speed for a maximum of 1 minute. After that, the coastdown run shall be started immediately.

4.3.2.4.2. During a coastdown run, the transmission shall be in neutral. Any steering wheel movement shall be avoided as much as possible, and the vehicle’s brakes shall not be operated.

4.3.2.4.3. Although it is recommended that each coastdown run be performed without interruption, if data cannot be collected in a single run for all the reference speed points the coastdown test may be performed with coastdown runs where the first and last reference speeds are not necessarily the highest and lowest reference speeds. For split runs, the following additional requirements shall apply: (a) At least one reference speed in each coastdown run shall overlap with the immediately higher speed range coastdown run. This reference speed shall be referred to as a split point; (b) At each overlapped reference speed, the average force of the immediately lower speed coastdown run shall not deviate from the average force of the immediately higher speed range coastdown run by ±10 N or ±5 per cent, whichever is greater; (c) Overlapped reference speed data of the lower speed coastdown run shall be used only for checking criterion (b) and shall be excluded from evaluation of the statistical precision as defined in paragraph 4.3.1.4.2. of this annex; (d) The overlapped speed may be less than 10 km/h but shall not be less than 5 km/h. In this case, overlap criterion (b) shall be checked by either extrapolating the polynomial curves for the lower and higher speed segment to a 10 km/h overlap, or by comparing the average force in the specific speed range.

4.3.2.4.4. It is recommended that coastdown runs should be conducted successively without undue delay between runs. If there is a delay between runs (e.g. for a driver break, checking vehicle integrity, etc.), the vehicle shall be warmed up again as described in paragraph 4.2.4. and the coastdown runs shall be re-commenced from this point.

4.3.2.5. Determination of the equation of motion

Symbols used in the on-board anemometer equations of motion are listed in Table A4/5.

Table A4/5

Symbols used in the on-board anemometer equations of motion

Symbol Units Description Af m2 frontal area of the vehicle a0 … an degrees-1 aerodynamic drag coefficients as a function of yaw angle Am N mechanical drag coefficient Bm N/(km/h) mechanical drag coefficient Cm N/(km/h)2 mechanical drag coefficient CD(Y) aerodynamic drag coefficient at yaw angle Y D N drag Daero N aerodynamic drag Df N front axle drag (including driveline) Dgrav N gravitational drag Dmech N mechanical drag Dr N rear axle drag (including driveline) Dtyre N tyre rolling resistance (dh/ds) - sine of the slope of the track in the direction of travel (+ indicates ascending) (dv/dt) m/s2 acceleration g m/s2 gravitational constant mav kg arithmetic average mass of the test vehicle before and after road load determination me kg effective vehicle mass including rotating components ρ kg/m3 air density t s time T K temperature v km/h vehicle speed vr km/h relative wind speed Y degrees yaw angle of apparent wind relative to direction of vehicle travel

4.3.2.5.1. General form The general form of the equation of motion is as follows: where: Dmech = Dtyre + Df + Dr; Daero = ; Dgrav = In the case that the slope of the test track is equal to or less than 0.1 per cent over its length, Dgrav may be set to zero.

4.3.2.5.2. Mechanical drag modelling Mechanical drag consisting of separate components representing tyre Dtyre and front and rear axle frictional losses Df and Dr (including transmission losses) shall be modelled as a three-term polynomial as a function of vehicle speed v as in the equation below: Dmech = Am + Bm v + Cm v2 where Am, Bm, and Cm are determined in the data analysis using the least squares method. These constants reflect the combined driveline and tyre drag. In the case that the tested vehicle is the representative vehicle of a road load matrix family, the coefficient Bm shall be set to zero and the coefficients Am and Cm shall be recalculated with a least squares regression analysis.

4.3.2.5.3. Aerodynamic drag modelling The aerodynamic drag coefficient CD(Y) shall be modelled as a five-term polynomial as a function of yaw angle Y as in the equation below: CD(Y) = a0 + a1Y + a2Y2 + a3Y3 + a4Y4 a0 to a4 are constant coefficients whose values are determined in the data analysis. The aerodynamic drag shall be determined by combining the drag coefficient with the vehicle’s frontal area Af and the relative wind velocity vr.

4.3.2.5.4. Final equation of motion Through substitution, the final form of the equation of motion becomes:

4.3.2.6. Data reduction

A three-term equation shall be generated to describe the road load force as a function of velocity, F = A + Bv + Cv2, corrected to standard ambient temperature and pressure conditions, and in still air. The method for this analysis process is described in paragraphs 4.3.2.6.1. to 4.3.2.6.10. inclusive of this annex.

4.3.2.6.1. Determining calibration coefficients If not previously determined, calibration factors to correct for vehicle blockage shall be determined for relative wind speed and yaw angle. Vehicle speed v, relative wind velocity vr and yaw Y measurements during the warm-up phase of the test procedure shall be recorded. Paired runs in alternate directions on the test track at a constant velocity of 80 km/h shall be performed, and the arithmetic average values of v, vr and Y for each run shall be determined. Calibration factors that minimize the total errors in head and cross winds over all the run pairs, i.e. the sum of (headi – headi+1)2, etc., shall be selected where headi and headi+1 refer to wind speed and wind direction from the paired test runs in opposing directions during the vehicle warm-up/stabilization prior to testing.

4.3.2.6.2. Deriving second by second observations From the data collected during the coastdown runs, values for v, , vr 2, and Y shall be determined by applying calibration factors obtained in paragraphs 4.3.2.1.3. and 4.3.2.1.4. of this annex. Data filtering shall be used to adjust samples to a frequency of 1 Hz.

4.3.2.6.3. Preliminary analysis Using a linear least squares regression technique, all data points shall be analysed at once to determine Am, Bm, Cm, a0, a1, a2, a3 and a4 given me, , , v, vr and ρ.

4.3.2.6.4. Data outliers A predicted force me shall be calculated and compared to the observed data points. Data points with excessive deviations, e.g., over three standard deviations, shall be flagged.

4.3.2.6.5. Data filtering (optional) Appropriate data filtering techniques may be applied and the remaining data points shall be smoothed out.

4.3.2.6.6. Data elimination Data points gathered where yaw angles are greater than ±20 degrees from the direction of vehicle travel shall be flagged. Data points gathered where relative wind is less than + 5 km/h (to avoid conditions where tailwind speed is higher than vehicle speed) shall also be flagged. Data analysis shall be restricted to vehicle speeds within the speed range selected according to paragraph 4.3.2.2. of this annex.

4.3.2.6.7. Final data analysis All data that has not been flagged shall be analysed using a linear least squares regression technique. Given me, , , v, vr and ρ, Am, Bm, Cm, a0, a1, a2, a3 and a4 shall be determined.

4.3.2.6.8. Constrained analysis (optional) To better separate the vehicle aerodynamic and mechanical drag, a constrained analysis may be applied such that the vehicle’s frontal area Af and the drag coefficient CD may be fixed if they have been previously determined.

4.3.2.6.9. Correction to reference conditions Equations of motion shall be corrected to reference conditions as specified in paragraph 4.5. of this annex.

4.3.2.6.10. Statistical criteria for on-board anemometry The exclusion of each single pair of coastdown runs shall change the calculated road load for each coastdown reference speed vj less than the convergence requirement, for all i and j: where: ΔF(vj) is the difference between the calculated road load with all coastdown runs and the calculated road load with the ith pair of coastdown runs excluded, N; F(vj) is the calculated road load with all coastdown runs included, N; vj is the reference speed, km/h; n is the number of pairs of coastdown runs, all valid pairs are included. In the case that the convergence requirement is not met, pairs shall be removed from the analysis, starting with the pair giving the highest change in calculated road load, until the convergence requirement is met, as long as a minimum of 5 valid pairs are used for the final road load determination.

4.4. Measurement and calculation of running resistance using the torque meter method

As an alternative to the coastdown methods, the torque meter method may also be used in which the running resistance is determined by measuring wheel torque on the driven wheels at the reference speed points for time periods of at least 5 seconds.

4.4.1. Installation of torque meters

Wheel torque meters shall be installed between the wheel hub and the wheel of each driven wheel, measuring the required torque to keep the vehicle at a constant speed.

The torque meter shall be calibrated on a regular basis, at least once a year, traceable to national or international standards, in order to meet the required accuracy and precision.

4.4.2. Procedure and data sampling

4.4.2.1. Selection of reference speeds for running resistance curve determination

Reference speed points for running resistance determination shall be selected according to paragraph 2.2. of this annex.

The reference speeds shall be measured in descending order. At the request of the manufacturer, there may be stabilization periods between measurements but the stabilization speed shall not exceed the speed of the next reference speed.

4.4.2.2. Data collection

Data sets consisting of actual speed vji actual torque Cji and time over a period of at least 5 seconds shall be measured for every vj at a sampling frequency of at least 10 Hz. The data sets collected over one time period for a reference speed vj shall be referred to as one measurement.

4.4.2.3. Vehicle torque meter measurement procedure

Prior to the torque meter method test measurement, a vehicle warm-up shall be performed according to paragraph 4.2.4. of this annex.

During test measurement, steering wheel movement shall be avoided as much as possible, and the vehicle brakes shall not be operated.

The test shall be repeated until the running resistance data satisfy the measurement precision requirements as specified in paragraph 4.4.3.2. of this annex.

4.4.2.4. Velocity deviation

During a measurement at a single reference speed point, the velocity deviation from the arithmetic average velocity (vji-vjm) calculated according to paragraph 4.4.3. of this annex, shall be within the values in Table A4/6.

Additionally, the arithmetic average velocity vjm at every reference speed point shall not deviate from the reference speed vj by more than ±1 km/h or 2 per cent of the reference speed vj, whichever is greater.

Table A4/6

Velocity deviation

Time period, s Velocity deviation, km/h 5 - 10 ±0.2 10 - 15 ±0.4 15 - 20 ±0.6 20 - 25 ±0.8 25 - 30 ±1.0 ≥ 30 ±1.2

4.4.2.5. Atmospheric temperature

Tests shall be performed under the same temperature conditions as defined in paragraph 4.1.1.2. of this annex.

4.4.3. Calculation of arithmetic average velocity and arithmetic average torque

4.4.3.1. Calculation process

Arithmetic average velocity vjm, km/h, and arithmetic average torque Cjm, in Nm, of each measurement shall be calculated from the data sets collected according to the requirements of paragraph 4.4.2.2. of this annex using the following equations:

and

where:

vji is the actual vehicle speed of the ith data set at reference speed point j, km/h; k is the number of data sets in a single measurement; Cji is the actual torque of the ith data set, Nm; Cjs is the compensation term for speed drift, Nm, given by the following equation: Cjs = (mst + mr) × αjrj shall be no greater than 0.05 and may be disregarded if αj is not greater than ±0.005 m/s2; mst is the test vehicle mass at the start of the measurements and shall be measured immediately before the warm-up procedure and no earlier, kg; mr is the equivalent effective mass of rotating components according to paragraph 2.5.1. of this annex, kg; rj is the dynamic radius of the tyre determined at a reference point of 80 km/h or at the highest reference speed point of the vehicle if this speed is lower than 80 km/h, calculated using the following equation:

where:

n is the rotational frequency of the driven tyre, s-1; αj is the arithmetic average acceleration, m/s2, calculated using the following equation:

where:

ti is the time at which the ith data set was sampled, s.

4.4.3.2. Measurement precision

The measurements shall be carried out in opposite directions until a minimum of three pairs of measurements at each reference speed vi have been obtained, for which satisfies the precision ρj according to the following equation:

where:

n is the number pairs of measurements for Cjm; is the running resistance at the speed vi, Nm, given by the equation:

where:

Cjmi is the arithmetic average torque of the ith pair of measurements at speed vj, Nm, and given by:

where:

Cjmai and Cjmbi are the arithmetic average torques of the ith measurement at speed vj determined in paragraph 4.4.3.1. of this annex for each direction, a and b respectively, Nm; s is the standard deviation, Nm, calculated using the following equation: h is a coefficient as a function of n as given in Table A4/4 in paragraph 4.3.1.4.2. of this annex.

4.4.4. Running resistance curve determination

The arithmetic average speed and arithmetic average torque at each reference speed point shall be calculated using the following equations:

Vjm = ½ × (vjma + vjmb)

Cjm = ½ × (Cjma +Cjmb)

The following least squares regression curve of arithmetic average running resistance shall be fitted to all the data pairs (Vjm, Cjm) at all reference speeds described in paragraph 4.4.2.1. of this annex to determine the coefficients c0, c1 and c2.

The coefficients, c0, c1 and c2 as well as the coastdown times measured on the chassis dynamometer (see paragraph 8.2.4. of this annex) shall be recorded.

In the case that the tested vehicle is the representative vehicle of a road load matrix family, the coefficient c1 shall be set to zero and the coefficients c0 and c2 shall be recalculated with a least squares regression analysis.

4.5. Correction to reference conditions and measurement equipment

4.5.1. Air resistance correction factor

The correction factor for air resistance K2 shall be determined using the following equation:

where:

T is the arithmetic average atmospheric temperature of all individual runs, Kelvin (K); P is the arithmetic average atmospheric pressure, kPa.

4.5.2. Rolling resistance correction factor

The correction factor K0 for rolling resistance, in Celsius–1 (C–1), may be determined based on empirical data and approved by the responsible authority for the particular vehicle and tyre combination to be tested, or may be assumed to be as follows:

K0 = 8.6 × 10–3 °C–1

4.5.3. Wind correction

4.5.3.1. Wind correction when using stationary anemometry

Wind correction may be waived when the arithmetic average wind speed for each valid run pair is 2 m/s or less. In the case that wind speed is measured at more than one part of the test track, such as when the test is performed on an oval test track (see paragraph 4.1.1.1.1. of this annex), the wind speed shall be averaged at each measurement location and the higher of two average wind speeds shall be used to determine whether a wind speed correction is to be applied or may be waived.

4.5.3.1.1. The wind resistance correction W 1 for the coastdown method or W 2 for the torque meter method shall be calculated using the following equations: or: where: w1 is the wind resistance correction for the coastdown method, N; f2 is the coefficient of the aerodynamic term determined according to paragraph 4.3.1.4.4. of this annex; vw in the case that wind speed is measured at only one point, vw is the arithmetic average vector component of the wind speed parallel to the test road during all valid run pairs, m/s; vw in the case that the wind speed is measured at two points, vw is the lower of the two arithmetic average vector components of the wind speed parallel to the test road during all valid run pairs, m/s; W2 is the wind resistance correction for the torque meter method, Nm; c2 is the coefficient of the aerodynamic term for the torque meter method determined according to paragraph 4.4.4. of this annex.

4.5.3.2. Wind correction when using on-board anemometry

In the case that the coastdown method is based on on-board anemometry, w1 and w2 in the equations in paragraph 4.5.3.1.1. of this annex shall be set to zero, as the wind correction is already applied according to paragraph 4.3.2. of this annex.

4.5.4. Test mass correction factor

The correction factor K1 for the test mass of the test vehicle shall be determined using the following equation:

where:

TM is the test mass of the test vehicle, kg; mav is the arithmetic average of the test vehicle masses at the beginning and end of road load determination, kg.

4.5.5. Road load curve correction

4.5.5.1. The curve determined in paragraph 4.3.1.4.4. of this annex shall be corrected to reference conditions as follows:

where:

F* is the corrected road load, N; f0 is the constant road load coefficient, N; f1 is the first order road load coefficient, N/(km/h); f2 is the second order road load coefficient, N/(km/h)2; K0 is the correction factor for rolling resistance as defined in paragraph 4.5.2. of this annex; K1 is the test mass correction as defined in paragraph 4.5.4. of this annex; K2 is the correction factor for air resistance as defined in paragraph 4.5.1. of this annex; T is the arithmetic average atmospheric temperature during all valid run pairs, °C; v is vehicle velocity, km/h; W1 is the wind resistance correction as defined in paragraph 4.5.3. of this annex, N.

The result of the calculation below shall be used as the target road load coefficient At in the calculation of the chassis dynamometer load setting described in paragraph 8.1. of this annex:

The result of the calculation below shall be used as the target road load coefficient Bt in the calculation of the chassis dynamometer load setting described in paragraph 8.1. of this annex:

(f1 × (1 + K0 × (T-20))).

The result of the calculation below shall be used as the target road load coefficient Ct in the calculation of the chassis dynamometer load setting described in paragraph 8.1. of this annex:

(K2 × f2).

4.5.5.2. The curve determined in paragraph 4.4.4. of this annex shall be corrected to reference conditions and measurement equipment installed according to the following procedure.

4.5.5.2.1. Correction to reference conditions where: C* is the corrected running resistance, Nm; C0 is the constant term as determined in paragraph 4.4.4. of this annex, Nm; C1 is the coefficient of the first order term as determined in paragraph 4.4.4. of this annex, Nm/(km/h); C2 is the coefficient of the second order term as determined in paragraph 4.4.4. of this annex, Nm/(km/h)2; K0 is the correction factor for rolling resistance as defined in paragraph 4.5.2. of this annex; K1 is the test mass correction as defined in paragraph 4.5.4. of this annex; K2 is the correction factor for air resistance as defined in paragraph 4.5.1. of this annex; v is the vehicle velocity, km/h; T is the arithmetic average atmospheric temperature during all valid run pairs, °C; W2 is the wind resistance correction as defined in paragraph 4.5.3. of this annex.

4.5.5.2.2. Correction for installed torque meters If the running resistance is determined according to the torque meter method, the running resistance shall be corrected for effects of the torque measurement equipment installed outside the vehicle on its aerodynamic characteristics. The running resistance coefficient c2 shall be corrected using the following equation: c2corr = K2 × c2 × (1 + (Δ(CD × Af))/(CD’ × Af’)) where: Δ(CD × Af) = (CD × Af) - (CD’ × Af’); CD’ × Af’ is the product of the aerodynamic drag coefficient multiplied by the frontal area of the vehicle with the torque meter measurement equipment installed measured in a wind tunnel fulfilling the criteria of paragraph 3.2. of this annex, m2; CD × Af is the product of the aerodynamic drag coefficient multiplied by the frontal area of the vehicle with the torque meter measurement equipment not installed measured in a wind tunnel fulfilling the criteria of paragraph 3.2. of this annex, m2.

4.5.5.2.3. Target running resistance coefficients The result of the calculation below shall be used as the target running resistance coefficient at in the calculation of the chassis dynamometer load setting described in paragraph 8.2. of this annex: The result of the calculation below shall be used as the target running resistance coefficient bt in the calculation of the chassis dynamometer load setting described in paragraph 8.2. of this annex: (c1 × (1 + K0 × (T-20))). The result of the calculation below shall be used as the target running resistance coefficient ct in the calculation of the chassis dynamometer load setting described in paragraph 8.2. of this annex: (c2corr × r).

5. Method for the calculation of road load or running resistance based on vehicle parameters

5.1. Calculation of road load and running resistance for vehicles based on a representative vehicle of a road load matrix family If the road load of the representative vehicle is determined according to a coastdown method described in paragraph 4.3. of this annex or according to the wind tunnel method described in paragraph 6. of this annex, the road load of an individual vehicle shall be calculated according to paragraph 5.1.1. of this annex. If the running resistance of the representative vehicle is determined according to the torque meter method described in paragraph 4.4. of this annex, the running resistance of an individual vehicle shall be calculated according to paragraph 5.1.2. of this annex.

5.1.1. For the calculation of the road load of vehicles of a road load matrix family, the vehicle parameters described in paragraph 4.2.1.4. of this annex and the road load coefficients of the representative test vehicle determined in paragraph 4.3. of this annex shall be used.

5.1.1.1. The road load force for an individual vehicle shall be calculated using the following equation: Fc = f0 + (f1 × v) + (f2 × v2) where: Fc is the calculated road load force as a function of vehicle velocity, N; f0 is the constant road load coefficient, N, defined by the equation: f0 = Max((0.05 × f0r + 0.95 × (f0r × TM/TMr + × 9.81 × TM)); (0.2 × f0r + 0.8 × (f0r × TM/TMr + × 9.81 × TM))) f0r is the constant road load coefficient of the representative vehicle of the road load matrix family, N; f1 is the first order road load coefficient, N/(km/h), and shall be set to zero; f2 is the second order road load coefficient, N/(km/h)2, defined by the equation: f2 = Max((0.05 × f2r + 0.95 × f2r × Af / Afr); (0.2 × f2r + 0.8 × f2r × Af / Afr)) f2r is the second order road load coefficient of the representative vehicle of the road load matrix family, N/(km/h)2; v is the vehicle speed, km/h; TM is the actual test mass of the individual vehicle of the road load matrix family, kg; TMr is the test mass of the representative vehicle of the road load matrix family, kg; Af is the frontal area of the individual vehicle of the road load matrix family, m2, Afr is the frontal area of the representative vehicle of the road load matrix family, m2; RR is the tyre rolling resistance of the individual vehicle of the road load matrix family, kg/tonne; RRr is the tyre rolling resistance of the representative vehicle of the road load matrix family, kg/tonne. For the tyres fitted to an individual vehicle, the value of the rolling resistance RR shall be set to the class value of the applicable tyre energy efficiency class according to Table A4/2 of Annex B4. If the tyres on the front and rear axles belong to different energy efficiency classes, the weighted mean shall be used, calculated using the equation in paragraph 3.2.3.2.2.2. of Annex B7. If the same tyres were fitted to test vehicles L and H, the value of RRind when using the interpolation method shall be set to RRH.

5.1.2. For the calculation of the running resistance of vehicles of a road load matrix family, the vehicle parameters described in paragraph 4.2.1.4. of this annex and the running resistance coefficients of the representative test vehicle determined in paragraph 4.4. of this annex shall be used.

5.1.2.1. The running resistance for an individual vehicle shall be calculated using the following equation: Cc = c0 + c1 × v + c2 × v2 where: Cc is the calculated running resistance as a function of vehicle velocity, Nm; c0 is the constant running resistance coefficient, Nm, defined by the equation: c0 = r’/1.02 × Max((0.05 × 1.02 × c0r/r’ + 0.95 × (1.02 × c0r/r’ × TM/TMr + × 9.81 × TM)); (0.2 × 1.02 × c0r/r’ + 0.8 × (1.02 × c0r/r’ × TM/TMr + × 9.81 × TM))) c0r is the constant running resistance coefficient of the representative vehicle of the road load matrix family, Nm; c1 is the first order running resistance coefficient, Nm/(km/h), and shall be set to zero; c2 is the second order running resistance coefficient, Nm/(km/h)2, defined by the equation: c2 = r’/1.02 × Max((0.05 × 1.02 × c2r/r’ + 0.95 × 1.02 × c2r/r’ × Af / Afr); (0.2 × 1.02 × c2r/r’ + 0.8 × 1.02 ×c2r/r’ × Af / Afr)) c2r is the second order running resistance coefficient of the representative vehicle of the road load matrix family, N/(km/h)2; v is the vehicle speed, km/h; TM is the actual test mass of the individual vehicle of the road load matrix family, kg; TMr is the test mass of the representative vehicle of the road load matrix family, kg; Af is the frontal area of the individual vehicle of the road load matrix family, m2; Afr is the frontal area of the representative vehicle of the road load matrix family, m2; RR is the tyre rolling resistance of the individual vehicle of the road load matrix family, kg/tonne; RRr is the tyre rolling resistance of the representative vehicle of the road load matrix family, kg/tonne; r’ is the dynamic radius of the tyre on the chassis dynamometer obtained at 80 km/h, m; 1.02 is an approximate coefficient compensating for drivetrain losses.

5.2. Calculation of the default road load based on vehicle parameters

5.2.1. As an alternative for determining road load with the coastdown or torque meter method, a calculation method for default road load may be used. For the calculation of a default road load based on vehicle parameters, several parameters such as test mass, width and height of the vehicle shall be used. The default road load Fc shall be calculated for the reference speed points.

5.2.2. The default road load force shall be calculated using the following equation: Fc = f0 + (f1 × v) + (f2 × v2) where: Fc is the calculated default road load force as a function of vehicle velocity, N; f0 is the constant road load coefficient, N, defined by the following equation: f0 = 0.140 × TM; f1 is the first order road load coefficient, N/(km/h), and shall be set to zero; f2 is the second order road load coefficient, N/(km/h)2, defined by the following equation: f2 = (2.8 × 10–6 × TM) + (0.0170 × width × height); v is vehicle velocity, km/h; TM test mass, kg; width vehicle width as defined in term No. 6.2. of Standard ISO 612:1978, m; height vehicle height as defined in term No. 6.3. of Standard ISO 612:1978, m.

6. Wind tunnel method

The wind tunnel method is a road load measurement method using a combination of a wind tunnel and a chassis dynamometer or of a wind tunnel and a flat belt dynamometer. The test benches may be separate facilities or integrated with one another.

6.1. Measurement method

6.1.1. The road load shall be determined by: (a) Adding the road load forces measured in a wind tunnel and those measured using a flat belt dynamometer; or (b) Adding the road load forces measured in a wind tunnel and those measured on a chassis dynamometer.

6.1.2. Aerodynamic drag shall be measured in the wind tunnel.

6.1.3. Rolling resistance and drivetrain losses shall be measured using a flat belt or a chassis dynamometer, measuring the front and rear axles simultaneously.

6.2. Approval of the facilities by the responsible authority

The results of the wind tunnel method shall be compared to those obtained using the coastdown method to demonstrate qualification of the facilities and recorded.

6.2.1. Three vehicles shall be selected by the responsible authority. The vehicles shall cover the range of vehicles (e.g. size, weight) planned to be measured with the facilities concerned.

6.2.2. Two separate coastdown tests shall be performed with each of the three vehicles according to paragraph 4.3. of this annex, and the resulting road load coefficients, f 0 , f 1 and f 2 , shall be determined according to that paragraph and corrected according to paragraph 4.5.5. of this annex. The coastdown test result of a test vehicle shall be the arithmetic average of the road load coefficients of its two separate coastdown tests. If more than two coastdown tests are necessary to fulfil the approval of facilities' criteria, all valid tests shall be averaged.

6.2.3. Measurement with the wind tunnel method according to paragraphs 6.3. to 6.7. inclusive of this annex shall be performed on the same three vehicles as selected in paragraph 6.2.1. of this annex and in the same conditions, and the resulting road load coefficients, f 0 , f 1 and f 2 , shall be determined. If the manufacturer chooses to use one or more of the available alternative procedures within the wind tunnel method (i.e. paragraph 6.5.2.1. on preconditioning, paragraphs 6.5.2.2. and 6.5.2.3. on the procedure, including paragraph 6.5.2.3.3. on dynamometer setting), these procedures shall also be used also for the approval of the facilities.

6.2.4. Approval criteria The facility or combination of facilities used shall be approved if both of the following two criteria are fulfilled: (a) The difference in cycle energy, expressed as εk, between the wind tunnel method and the coastdown method shall be within ±0.05 for each of the three vehicles k according to the following equation: where: εk is the difference in cycle energy over a complete Class 3 WLTC for vehicle k between the wind tunnel method and the coastdown method, per cent; Ek,WTM is the cycle energy over a complete Class 3 WLTC for vehicle k, calculated with the road load derived from the wind tunnel method (WTM) calculated according to paragraph 5. of Annex B7, J; Ek,coastdown is the cycle energy over a complete Class 3 WLTC for vehicle k, calculated with the road load derived from the coastdown method calculated according to paragraph 5. of Annex B7, J.; and (b) The arithmetic average of the three differences shall be within 0.02. The approval shall be recorded by the responsible authority including measurement data and the facilities concerned. The facility may be used for road load determination for a maximum of two years after the approval has been granted. Each combination of roller chassis dynamometer or moving belt and wind tunnel shall be approved separately. Every combination of wind speeds (see paragraph 6.4.3. of this annex) used for the determination of road load values shall be validated separately.

6.3. Vehicle preparation and temperature

Conditioning and preparation of the vehicle shall be performed according to paragraphs 4.2.1. and 4.2.2. of this annex and applies to both the flat belt or roller chassis dynamometers and the wind tunnel measurements.

In the case that the alternative warm-up procedure described in paragraph 6.5.2.1. of this annex is applied, the target test mass adjustment, the weighing of the vehicle and the measurement shall all be performed without the driver in the vehicle.

The flat belt or the chassis dynamometer test cells shall have a temperature set point of 20 °C with a tolerance of ±3 °C. At the request of the manufacturer, the set point may also be 23 °C with a tolerance of ±3 °C.

6.4. Wind tunnel procedure

6.4.1. Wind tunnel criteria The wind tunnel design, test methods and the corrections shall provide a value of (CD × Af) representative of the on-road (CD × Af) value and with a repeatability of ±0.015 m2. For all (CD × Af) measurements, the wind tunnel criteria listed in paragraph 3.2. of this annex shall be met with the following modifications: (a) The solid blockage ratio described in paragraph 3.2.4. of this annex shall be less than 25 per cent; (b) The belt surface contacting any tyre shall exceed the length of that tyre's contact area by at least 20 per cent and shall be at least as wide as that contact patch; (c) The standard deviation of total air pressure at the nozzle outlet described in paragraph 3.2.8. of this annex shall be less than 1 per cent; (d) The restraint system blockage ratio described in paragraph 3.2.10. of this annex shall be less than 3 per cent; (e) Additionally to the requirement defined in paragraph 3.2.11. of this annex, when measuring Class 1 vehicles, the precision of the measured force shall not exceed ±2.0 N.

6.4.2. Wind tunnel measurement The vehicle shall be in the condition described in paragraph 6.3. of this annex. The vehicle shall be placed parallel to the longitudinal centre line of the tunnel with a maximum tolerance of ±10 mm. The vehicle shall be placed with a yaw angle of 0 ° within a tolerance of ±0.1 °. Aerodynamic drag shall be measured for at least for 60 seconds and at a minimum frequency of 5 Hz. Alternatively, the drag may be measured at a minimum frequency of 1 Hz and with at least 300 subsequent samples. The result shall be the arithmetic average of the drag. Prior to a test it shall be checked that at the aerodynamic force measured at a wind speed of 0 km/h yields a result equal to 0 Newtons. In the case that the vehicle has movable aerodynamic body parts, paragraph 4.2.1.5. of this annex shall apply. Where movable parts are velocity-dependent, every applicable position shall be measured in the wind tunnel and evidence shall be provided to the responsible authority indicating the relationship between reference speed, movable part position, and the corresponding (CD × Af).

6.4.3. Wind speeds for wind tunnel measurement The aerodynamic force shall be measured at two wind speeds under the following speed conditions: (a) Class 1 vehicles Lower wind speed vlow to measure aerodynamic force shall be vlow < 80 km/h; Higher wind speed vhigh shall be (vlow + 40 km/h ≤ vhigh ≤ 150 km/h). (b) Class 2 and 3 vehicles Lower wind speed vlow to measure aerodynamic force shall be 80 km/h ≤ vlow ≤ 100 km/h; Higher wind speed shall be (vlow + 40 km/h ≤ vhigh ≤ 150 km/h).

6.5. Flat belt applied for the wind tunnel method

6.5.1. Flat belt criteria

6.5.1.1. Description of the flat belt test bench The wheels shall rotate on flat belts that do not change the rolling characteristics of the wheels compared to those on the road. The measured forces in the x-direction shall include the frictional forces in the drivetrain.

6.5.1.2. Vehicle restraint system The dynamometer shall be equipped with a centring device aligning the vehicle within a tolerance of ±0.5 degrees of rotation around the z-axis. The restraint system shall maintain the centred drive wheel position throughout the coastdown runs of the road load determination within the following limits:

6.5.1.2.1. Lateral position (y-axis) The vehicle shall remain aligned in the y-direction and lateral movement shall be minimised.

6.5.1.2.2. Front and rear position (x-axis) Additional to the requirement of paragraph 6.5.1.2.1. of this annex, both wheel axes shall be within ±10 mm of the belt’s lateral centre lines.

6.5.1.2.3. Vertical force The restraint system shall be designed so as to impose no vertical force on the drive wheels.

6.5.1.3. Accuracy of measured forces Only the reaction force for turning the wheels shall be measured. No external forces shall be included in the result (e.g. force of the cooling fan air, vehicle restraints, aerodynamic reaction forces of the flat belt, dynamometer losses, etc.). The force in the x-direction shall be measured with an accuracy of ±5 N.

6.5.1.4. Flat belt speed control The belt speed shall be controlled with an accuracy of ±0.1 km/h.

6.5.1.5. Flat belt surface The flat belt surface shall be clean, dry and free from foreign material that might cause tyre slippage.

6.5.1.6. Cooling A current of air of variable speed shall be blown towards the vehicle. The set point of the linear velocity of the air at the blower outlet shall be equal to the corresponding dynamometer speed above measurement speeds of 5 km/h. The linear velocity of the air at the blower outlet shall be within ±5 km/h or ±10 per cent of the corresponding measurement speed, whichever is greater.

6.5.2. Flat belt measurement The measurement procedure may be performed according to either paragraph 6.5.2.2. or paragraph 6.5.2.3. of this annex.

6.5.2.1. Preconditioning The vehicle shall be conditioned on the dynamometer as described in paragraphs 4.2.4.1.1. to 4.2.4.1.3. inclusive of this annex. The dynamometer load setting Fd for the preconditioning shall be: Fd = ad + (bd × v) + (cd × v2) where in the case of applying paragraph 6.7.2.1: ad = 0 bd = f1a; cd = f2a; or, where in the case of applying paragraph 6.7.2.2.: ad = 0 bd = 0 The equivalent inertia of the dynamometer shall be the test mass. The aerodynamic drag used for the load setting shall be determined in accordance with paragraph 6.7.2. of this annex and may be set directly as input. Otherwise, ad, bd, and cd from this paragraph shall be used. At the request of the manufacturer, as an alternative to paragraph 4.2.4.1.2. of this annex, the warm-up may be conducted by driving the vehicle with the flat belt. In this case, the warm-up speed shall be 110 per cent of the maximum speed of the applicable WLTC. The warm up is considered complete when the vehicle has been driven for at least 1,200 seconds and the change of measured force over a period of 200 seconds is less than 5 N.

6.5.2.2. Measurement procedure with stabilised speeds

6.5.2.2.1. The test shall be conducted from the highest to the lowest reference speed point.

6.5.2.2.2. Immediately after the measurement at the previous speed point, the deceleration from the current to the next applicable reference speed point shall be performed in a smooth transition of approximately 1 m/s 2 .

6.5.2.2.3. The reference speed shall be stabilised for at least 4 seconds and for a maximum of 10 seconds. The measurement equipment shall ensure that the signal of the measured force is stabilised after that period.

6.5.2.2.4. The force at each reference speed shall be measured for at least 6 seconds while the vehicle speed is kept constant. The resulting force for that reference speed point F jDyno shall be the arithmetic average of the force during the measurement.

6.5.2.2.5. The steps in paragraphs 6.5.2.2.2. to 6.5.2.2.4. inclusive of this annex shall be repeated for each reference speed.

6.5.2.3. Measurement procedure by deceleration

6.5.2.3.1. Preconditioning and dynamometer setting shall be performed according to paragraph 6.5.2.1. of this annex. Prior to each coastdown, the vehicle shall be driven at the highest reference speed or, in the case that the alternative warm-up procedure is used at 110 per cent of the highest reference speed, for at least 1 minute. The vehicle shall be subsequently accelerated to at least 10 km/h above the highest reference speed and the coastdown shall be started immediately.

6.5.2.3.2. The measurement shall be performed according to paragraphs 4.3.1.3.1. to 4.3.1.4.4. inclusive of this annex but excluding paragraph 4.3.1.4.2., where Δt ja and Δt jb are replaced by Δt j . The measurement shall be stopped after two decelerations if the force of both coastdowns at each reference speed point is within ±10 N, otherwise at least three coastdowns shall be performed using the criteria set out in paragraph 4.3.1.4.2. of this annex.

6.5.2.3.3. The force f jDyno at each reference speed v j shall be calculated by removing the dynamometer set force: fjDyno = fjDecel – fdj where: fjDecel is the force determined according to the equation calculating Fj in paragraph 4.3.1.4.4. of this annex at reference speed point j, N; fdj is the force determined to the equation calculating Fd in paragraph 6.5.2.1. of this annex at reference speed point j, N. Alternatively, at the request of the manufacturer, cd may be set to zero during the coastdown and for calculating fjDyno.

6.5.2.4. Measurement conditions The vehicle shall be in the condition described in paragraph 4.3.1.3.2. of this annex.

6.5.3. Measurement result of the flat belt method The result of the flat belt dynamometer fjDyno shall be referred to as fj for the further calculations in paragraph 6.7. of this annex.

6.6. Chassis dynamometer applied for the wind tunnel method

6.6.1. Criteria In addition to the descriptions in paragraphs 1. and 2. of Annex B5, the criteria described in paragraphs 6.6.1.1. to 6.6.1.6. shall apply.

6.6.1.1. Description of a chassis dynamometer The front and rear axles shall be equipped with a single roller with a diameter of not less than 1.2 metres.

6.6.1.2. Vehicle restraint system The dynamometer shall be equipped with a centring device aligning the vehicle. The restraint system shall maintain the centred drive wheel position within the following recommended limits throughout the coastdown runs of the road load determination:

6.6.1.2.1. Vehicle position The vehicle to be tested shall be installed on the chassis dynamometer roller as defined in paragraph 7.3.3. of this annex.

6.6.1.2.2. Vertical force The restraint system shall fulfil the requirements of paragraph 6.5.1.2.3. of this annex.

6.6.1.3. Accuracy of measured forces The accuracy of measured forces shall be as described in paragraph 6.5.1.3. of this annex apart from the force in the x-direction that shall be measured with an accuracy as described in paragraph 2.4.1. of Annex B5.

6.6.1.4. Dynamometer speed control The roller speeds shall be controlled with an accuracy of ±0.2 km/h.

6.6.1.5. Roller surface The roller surface shall be clean, dry and free from foreign material that might cause tyre slippage.

6.6.1.6. Cooling The cooling fan shall be as described in paragraph 6.5.1.6. of this annex.

6.6.2. Dynamometer measurement The measurement shall be performed as described in paragraph 6.5.2. of this annex.

6.6.3. Correcting measured chassis dynamometer forces to those on a flat surface The measured forces on the chassis dynamometer shall be corrected to a reference equivalent to the road (flat surface) and the result shall be referred to as fj. where: c1 is the tyre rolling resistance fraction of fjDyno; c2 is a chassis dynamometer-specific radius correction factor; fjDyno is the force calculated in paragraph 6.5.2.3.3. of this annex for each reference speed j, N; RWheel is one-half of the nominal design tyre diameter, m; RDyno is the radius of the chassis dynamometer roller, m. The manufacturer and the responsible authority shall agree on the factors c1 and c2 to be used, based on correlation test evidence provided by the manufacturer for the range of tyre characteristics intended to be tested on the chassis dynamometer. As an alternative the following conservative equation may be used: C2 shall be 0.2 except that 2.0 shall be used if the road load delta method (see paragraph 6.8. of this annex) is used and the road load delta calculated according to paragraph 6.8.1. of this annex is negative.

6.7. Calculations

6.7.1. Correction of the flat belt and chassis dynamometer results The measured forces determined in paragraphs 6.5. and 6.6. of this annex shall be corrected to reference conditions using the following equation: where: FDj is the corrected resistance measured at the flat belt or chassis dynamometer at reference speed j, N; fj is the measured force at reference speed j, N; K0 is the correction factor for rolling resistance as defined in paragraph 4.5.2. of this annex, K-1; K1 is the test mass correction as defined in paragraph 4.5.4. of this annex, N; T is the arithmetic average temperature in the test cell during the measurement, K.

6.7.2. Calculation of the aerodynamic force The calculation in paragraph 6.7.2.1. shall be applied considering the results of both wind speeds. However, if the difference of the product of the drag coefficient and frontal area (CD × Af) measured at the wind speeds vlow and vhigh is less than 0.015 m2, the calculation in paragraph 6.7.2.2. may be applied at the request of the manufacturer.

6.7.2.1. The aerodynamic force of each wind speed F 0wind , F low , and F high shall be calculated using the equation below. where: (CD × Af) is the product of the drag coefficient and frontal area measured in the wind tunnel at a certain reference speed point j, if applicable, m2; ρ0 is the dry air density defined in paragraph 3.2.10. of this Regulation, kg/m3; Fw is the aerodynamic force calculated at wind speed w, N; vw is the applicable wind speed, km/h. W is the reference to the applicable wind speed "0wind", "low" and "high"; F0wind is the aerodynamic force at 0 km/h, N; Flow is the aerodynamic force at vlow, N; Fhigh is the aerodynamic force at vhigh, N. The aerodynamic force coefficients f1a and f2a shall be calculated with a least square regression analysis using F0wind, Flow, and Fhigh and the equation below: F = f1a × v + f2a × v2 The final result for the aerodynamic force FAj shall be calculated with the equation below at each reference speed point vj. If the vehicle is equipped with velocity-dependent movable aerodynamic body parts, the corresponding aerodynamic force shall be applied for the reference speed points concerned. FAj = f1a × vj + f2a × v2 j

6.7.2.2. The aerodynamic force shall be calculated using the equation below, where the final (C D × A f ) of that wind speed shall be used that is also used for determination of optional equipment within the interpolation method. If the vehicle is equipped with velocity-dependent movable aerodynamic body parts, the corresponding (C D × A f ) values shall be applied for the reference speed points concerned. where: FAj is the aerodynamic force calculated at reference speed j, N; (CD × Af)j is the product of the drag coefficient and frontal area measured in the wind tunnel at a certain reference speed point j, if applicable, m2; ρ0 is the dry air density defined in paragraph 3.2.10. of this Regulation, kg/m3; vj is the reference speed j, km/h.

6.7.3. Calculation of road load values The total road load as a sum of the results of paragraphs 6.7.1 and 6.7.2. of this annex shall be calculated using the following equation: F* j = FDj + FAj for all applicable reference speed points j, N. For all calculated F* j, the coefficients f0, f1 and f2 in the road load equation shall be calculated with a least squares regression analysis and shall be used as the target coefficients in paragraph 8.1.1. of this annex. In the case that the vehicle tested according to the wind tunnel method is representative of a road load matrix family vehicle, the coefficient f1 shall be set to zero and the coefficients f0 and f2 shall be recalculated with a least squares regression analysis.

6.8. Road load delta method

For the purpose of including options when using the interpolation method which are not incorporated in the road load interpolation (i.e. aerodynamics, rolling resistance and mass), a delta in vehicle friction may be measured by the road load delta method (e.g. friction difference between brake systems). The following steps shall be performed:

(a) The friction of reference vehicle R shall be measured;

(b) The friction of the vehicle with the option (vehicle N) causing the difference in friction shall be measured;

(c) The difference shall be calculated according to paragraph 6.8.1. of this annex.

These measurements shall be performed on a flat belt according to paragraph 6.5. of this annex or on a chassis dynamometer according to paragraph 6.6. of this annex, and the correction of the results (excluding aerodynamic force) calculated according to paragraph 6.7.1. of this annex.

The application of this method is permitted only if the following criterion is fulfilled:

where:

FDj,R is the corrected resistance of vehicle R measured on the flat belt or chassis dynamometer at reference speed j calculated according to paragraph 6.7.1. of this annex, N; FDj,N is the corrected resistance of vehicle N measured on the flat belt or chassis dynamometer at reference speed j calculated according to paragraph 6.7.1. of this annex, N; n is the total number of speed points.

This alternative road load determination method may only be applied if vehicles R and N have identical aerodynamic resistance and if the measured delta appropriately covers the entire influence on the vehicle's energy consumption. This method shall not be applied if the overall accuracy of the absolute road load of vehicle N is compromised in any way.

6.8.1. Determination of delta flat belt or chassis dynamometer coefficients The delta road load shall be calculated using the following equation: FDj,Delta = FDj,N – FDj,R where: FDj,Delta is the delta road load at reference speed j, N; FDj,N is the corrected resistance measured on the flat belt or chassis dynamometer at reference speed j calculated according to paragraph 6.7.1. of this annex for vehicle N, N; FDj,R is the corrected resistance of the reference vehicle measured on the flat belt or chassis dynamometer at reference speed j calculated according to paragraph 6.7.1. of this annex for reference vehicle R, N. For all calculated FDj,Delta, the coefficients f0,Delta, f1,Delta and f2,Delta in the road load equation shall be calculated with a least squares regression analysis.

6.8.2. Determination of total road load If the interpolation method (see paragraph 3.2.3.2. of Annex B7) is not used, the road load coefficients for vehicle N shall be calculated according to the following equations: f0,N = f0,R – f0,Delta f1,N = f1,R – f1,Delta f2,N = f2,R – f2,Delta where: N refers to the road load coefficients of vehicle N; R refers to the road load coefficients of reference vehicle R; Delta refers to the delta road load coefficients determined in paragraph 6.8.1. of this annex.

7. Transferring road load to a chassis dynamometer

7.1. Preparation for chassis dynamometer test

7.1.0. Selection of dynamometer operation

The test shall be carried out in accordance with paragraph 2.4.2.4. of Annex B6.

7.1.1. Laboratory conditions

7.1.1.1. Roller(s) The chassis dynamometer roller(s) shall be clean, dry and free from foreign material that might cause tyre slippage. The dynamometer shall be run in the same coupled or uncoupled state as the subsequent Type 1 test. Chassis dynamometer speed shall be measured from the roller coupled to the power absorption unit.

7.1.1.1.1. Tyre slippage Additional weight may be placed on or in the vehicle to eliminate tyre slippage. The manufacturer shall perform the load setting on the chassis dynamometer with the additional weight. The additional weight shall be present for both load setting and the emissions and fuel consumption tests. The use of any additional weight shall be recorded.

7.1.1.2. Room temperature The laboratory atmospheric temperature shall be at a set point of 23 °C and shall not deviate by more than ±5 °C during the test unless otherwise required by any subsequent test.

7.2. Preparation of chassis dynamometer

7.2.1. Inertia mass setting

The equivalent inertia mass of the chassis dynamometer shall be set according to paragraph 2.5.3. of this annex. If the chassis dynamometer is not capable to meet the inertia setting exactly, the next higher inertia setting shall be applied with a maximum increase of 10 kg.

7.2.2. Chassis dynamometer warm-up

The chassis dynamometer shall be warmed up in accordance with the dynamometer manufacturer’s recommendations, or as appropriate, so that the frictional losses of the dynamometer may be stabilized.

7.3. Vehicle preparation

7.3.1. Tyre pressure adjustment

The tyre pressure at the soak temperature of a Type 1 test shall be set to no more than 50 per cent above the lower limit of the tyre pressure range for the selected tyre, as specified by the vehicle manufacturer (see paragraph 4.2.2.3. of this annex), and shall be recorded.

7.3.2. If the determination of dynamometer settings cannot meet the criteria described in paragraph 8.1.3. of this annex due to non-reproducible forces, the vehicle shall be equipped with a vehicle coastdown mode. The coastdown mode shall be approved by the responsible authority and its use shall be included in all relevant test reports.

If a vehicle is equipped with a vehicle coastdown mode, it shall be engaged both during road load determination and on the chassis dynamometer.

7.3.3. Vehicle placement on the dynamometer

The tested vehicle shall be placed on the chassis dynamometer in a straight ahead position and restrained in a safe manner.

7.3.3.1. In the case that a single roller chassis dynamometer is used, the vehicle shall be positioned and stay positioned throughout the procedure according to the requirements in 7.3.3.1.1. to 7.3.3.1.3.

7.3.3.1.1. Rotational alignment (rotation around z-axis) The vehicle shall be positioned in line with the x-axis in order to minimise rotation around the z-axis

7.3.3.1.2. Lateral position (y-axis) The vehicle shall remain aligned in the y-direction and lateral movement shall be minimised.

7.3.3.1.3. Front and rear position (x-axis) For all rotating wheels the centre of the tyre’s contact patch on the roller shall be within ±25 mm or ±2 per cent of the roller diameter, whichever is smaller, from the top of the roller.

7.3.3.1.4. The tested vehicle shall be restrained with a system compliant with paragraph 2.3.2. of Annex B5. If the torque meter method is used, the tyre pressure shall be adjusted such that the dynamic radius is within 0.5 per cent of the dynamic radius rj calculated using the equations in paragraph 4.4.3.1. of this annex at the 80 km/h reference speed point. The dynamic radius on the chassis dynamometer shall be calculated according to the procedure described in paragraph 4.4.3.1. of this annex. If this adjustment is outside the range defined in paragraph 7.3.1. of this annex, the torque meter method shall not apply.

7.3.4. Vehicle warm-up

7.3.4.1. The vehicle shall be warmed up with the applicable WLTC. In the case that the vehicle was warmed up at 90 per cent of the maximum speed of the next higher phase during the procedure defined in paragraph 4.2.4.1.2. of this annex, this higher phase shall be added to the applicable WLTC. Table A4/7 Vehicle warm-up Vehicle class Applicable WLTC Adopt next higher phase Warm-up cycle Class 1 Low1+ Medium1 NA Low1+ Medium1 Class 2 Low2 + Medium2 + High2 + Extra High2 NA Low2 + Medium2 + High2 + Extra High2 Low2 + Medium2 + High2 Yes (Extra High2) No Low2+ Medium2+ High2 Class 3 Low3 + Medium3 + High3 + Extra High3 Low3 + Medium3 + High3 + Extra High3 Low3 + Medium3 + High3 + Extra High3 Low3 + Medium3 + High3 Yes (Extra High3) No Low3 + Medium3 + High3

7.3.4.2. If the vehicle is already warmed up, the WLTC phase applied in paragraph 7.3.4.1. of this annex, with the highest speed, shall be driven.

7.3.4.3. Alternative warm-up procedure

7.3.4.3.1. At the request of the vehicle manufacturer and with approval of the responsible authority, an alternative warm-up procedure may be used. The approved alternative warm-up procedure may be used for vehicles within the same road load family and shall satisfy the requirements outlined in paragraphs 7.3.4.3.2. to 7.3.4.3.5. inclusive of this annex.

7.3.4.3.2. At least one vehicle representing the road load family shall be selected.

7.3.4.3.3. The cycle energy demand calculated according to paragraph 5. of Annex B7 with corrected road load coefficients f 0a , f 1a and f 2a , for the alternative warm-up procedure shall be equal to or higher than the cycle energy demand calculated with the target road load coefficients f 0 , f 1 , and f 2 , for each applicable phase. The corrected road load coefficients f0a, f1a and f2a, shall be calculated according to the following equations: f0a = f0 + Ad_alt – Ad_WLTC f1a = f1 + Bd_alt – Bd_WLTC f2a = f2 + Cd_alt – Cd_WLTC where: Ad_alt, Bd_alt and Cd_alt are the chassis dynamometer setting coefficients after the alternative warm-up procedure; Ad_WLTC, Bd_WLTC and Cd_WLTC are the chassis dynamometer setting coefficients after a WLTC warm-up procedure described in paragraph 7.3.4.1. of this annex and a valid chassis dynamometer load setting according to paragraph 8. of this annex.

7.3.4.3.4. The corrected road load coefficients f 0a , f 1a and f 2a , shall be used only for the purpose of paragraph 7.3.4.3.3. of this annex. For other purposes, the target road load coefficients f 0 , f 1 and f