Commission Delegated Regulation (EU) 2015/68Show full title

ANNEX VIII Requirements applying to the testing of inertia braking systems, braking devices and trailer braking couplings and of vehicles fitted with them as regards braking

1. General provisions

1.1. The inertia braking system of a towed vehicle comprises the control device, the transmission and the brake.

1.2. The control device is the aggregate of the components integral with the traction device (coupling head).

1.3. The transmission is the aggregate of the components comprised between the last part of the coupling head and the first part of the brake.

1.4. Braking systems in which accumulated energy (e.g. electric, pneumatic or hydraulic energy) is transmitted to the towed vehicle by the tractor and is controlled only by the thrust on the coupling do not constitute inertia braking systems within the meaning of this Regulation.

1.5. Tests

1.5.1. Determination of essential characteristics of the brake.

1.5.2. Determination of essential characteristics of the control device and verification of the conformity of the control device with the provisions of this Regulation.

1.5.3. Checking on the vehicle:

1.5.3.1.

the compatibility of the control device and the brake; and

1.5.3.2.

the transmission.

2. Symbols

2.1. Units used

2.1.1.

Mass: kg;

2.1.2.

Force: N;

2.1.3.

Acceleration due to gravity: g = 9,81 m/s²

2.1.4.

Torques and moments: Nm;

2.1.5.

Areas: cm²;

2.1.6.

Pressures: kPa;

2.1.7.

Lengths: unit specified in each case.

2.2. Symbols valid for all types of brakes (see Figure 1 of Appendix 1)

2.2.1. G_A

:

towed vehicle's technically permissible ‘maximum mass’ as declared by the manufacturer;

2.2.2. G′_A

:

towed vehicle's ‘maximum mass’ capable of being braked by the control device, as declared by the manufacturer;

2.2.3. G_B

:

towed vehicle's ‘maximum mass’ capable of being braked by joint operation of all of the towed vehicle's brakes

G_B = n · G_Bo

2.2.4. G_Bo

:

fraction of towed vehicle's permissible maximum mass capable of being braked by one brake, as declared by the manufacturer;

2.2.5. B*

:

required braking force;

2.2.6. B

:

required braking force taking account of rolling resistance;

2.2.7. D*

:

permissible thrust on coupling;

2.2.8. D

:

thrust on coupling;

2.2.9. P′

:

control device output force;

2.2.10. K

:

supplementary force of control device, conventionally designated by the force D corresponding to the point of intersection with the axis of the abscissae of the extrapolated curve expressing P′ in terms of D, measured with the device in the mid-travel position (see Figures 2 and 3 of Appendix 1);

2.2.11. K_A

:

force threshold of control device, i.e., the maximum thrust on the coupling head which can be applied for a short period of time without generating an output force from the control device. The symbol K_A is conventionally applied to the force measured when the coupling head begins to be pushed home at a speed of 10 to 15 mm/s, the control device transmission being uncoupled;

2.2.12. D₁

:

the maximum force applied to the coupling head when it is being pushed home at a speed of s mm/s + 10 %, the transmission being uncoupled;

2.2.13. D₂

:

the maximum force applied to the coupling head when it is being pulled at a speed of s mm/s + 10 % out of the position of maximum compression, the transmission being uncoupled;

2.2.14. η_Ho

:

efficiency of inertia control device;

2.2.15. η_H1

:

efficiency of transmission system;

2.2.16. η_H

:

overall efficiency of control device and transmission η_H = η_Ho · η_H1;

2.2.17. s

:

travel of control device in millimetres;

2.2.18. s′

:

effective (useful) travel of control device in millimetres, determined in the test report;

2.2.19. s″

:

spare travel of master cylinder, measured in millimetres at coupling head;

2.2.19.1. s_Hz

:

stroke of the master cylinder in millimetres according to Figure 8 of Appendix 1;

2.2.19.2. s″_Hz

:

spare travel of the master cylinder in millimetres at piston rod, according to Figure 8 of Appendix 1;

2.2.20. s_o

:

loss of travel, i.e., travel in millimetres of the coupling head when the latter is so actuated as to move from 300 mm above to 300 mm below the horizontal, the transmission remaining stationary;

2.2.21. 2s_B

:

brake-shoe lift (brake-shoe application travel), in millimetres, measured on diameter parallel to applying device, the brakes not being adjusted during the test;

2.2.22. 2s_B*

:

minimum brake shoe centre lift (minimum brake shoe application travel) (in millimetres) for wheel brakes with drum brakes

;

2r being the diameter of the brake drum in millimetres (see Figure 4 of Appendix 1).

For wheel brakes with disc brakes with hydraulic transmission

Where:

V₆₀

=

fluid volume absorbed by one wheel brake at a pressure corresponding to a braking force of 1,2 B* = 0,6 · G_Bo and a maximum tyre radius;

and

2r_A

=

outer diameter of brake disc (V₆₀ in cm³, F_RZ in cm² and r_A in mm).

2.2.23. M*

:

braking torque as specified by the manufacturer in point 5 of Appendix 3 of this Annex. This braking torque shall produce at least the prescribed braking force B*;

2.2.23.1. M_T

:

test braking torque in the case where no overload protector is fitted (according to point 6.2.1);

2.2.24. R

:

dynamic tyre rolling radius (m), as specified by the tyre manufacturer. As an alternative, if such information is not available, the value calculated by the formula: ‘ETRTO overall diameter/2’ may be used;

2.2.25. n

:

number of brakes.

2.2.26. M_r

:

maximum braking torque resulting from the maximum permissible travel s_r or the maximum permissible fluid volume V_r when the towed vehicle moves rearward (including rolling resistance = 0,01 · g · G_Bo);

2.2.27. s_r

:

maximum permissible travel at the brake control lever when the towed vehicle moves rearward;

2.2.28. V_r

:

maximum permissible fluid volume absorbed by one braking wheel when the towed vehicle moves rearward;

2.3. Symbols valid for mechanical-transmission braking systems (see Figure 5 of Appendix 1 )

2.3.1. i_Ho

:

reduction ratio between travel of coupling head and travel of lever at output side of control device;

2.3.2. i_H1

:

reduction ratio between travel of lever at output side of control device and travel of brake lever (gearing down of transmission);

2.3.3. i_H

:

reduction ratio between travel of coupling head and travel of brake lever

i_H = i_Ho · i_H1

2.3.4. i_g

:

reduction ratio between travel of brake lever and lift (application travel) at brake-shoe centre (see Figure 4 of Appendix 1);

2.3.5. P

:

force applied to the brake control lever; (see Figure 4 of Appendix 1);

2.3.6. P_o

:

brake-retraction force when the towed vehicle moves forward, i.e., in graph M = f(P), the value of the force P at the point of intersection of the extrapolation of this function with the abscissa (see Figure 6 of Appendix 1);

2.3.6.1. P_or

:

brake-retraction force when the towed vehicle moves rearward (see Figure 6 of Appendix 1);

2.3.7. P*

:

force applied to the brake control lever to produce the braking force B*;

2.3.8. P_T

:

test force according to point 6.2.1;

2.3.9. ρ

:

characteristic of the brake when the towed vehicle moves forward as defined from:

M = ρ (P – P_o)

2.3.9.1. ρ_r

:

characteristic of the brake when the towed vehicle moves rearward as defined from:

M_r = ρ_r (P_r – P_or)

2.3.10. s_cf

:

rear cable or rod travel at compensator when brakes operate in forward direction(1);

2.3.11. s_cr

:

rear cable or rod travel at compensator when brakes operate in rearward direction(1);

2.3.12. s_cd

:

differential travel at compensator when only one brake operates in the forward direction and the other in the reverse direction(1);

Where: s_{cd =} s_cr – s_cf (see Figure 5A of Appendix 1);

2.4. Symbols valid for hydraulic-transmission braking systems (see Figure 8 of Appendix 1)

2.4.1. i_h

:

reduction ratio between travel of coupling head and travel of piston in master cylinder;

2.4.2. i′_g

:

reduction ratio between travel of cylinder thrust point and lift (application travel) of brake-shoe centre;

2.4.3. F_RZ

:

surface area of piston of one wheel cylinder for drum brake(s); for disc brake(s), sum of the surface area of the caliper piston(s) on one side of the disc;

2.4.4. F_HZ

:

surface area of piston in master cylinder;

2.4.5. p

:

hydraulic pressure in brake cylinder;

2.4.6. p_o

:

retraction pressure in the brake cylinder when the towed vehicle moves forward; i.e., in graph of M = f(p), the value of the pressure p at the point of intersection of the extrapolation of this function with the abscissa (see Figure 7 of Appendix 1);

2.4.6.1. p_or

:

brake retraction pressure when the towed vehicle moves rearward (see Figure 7 of Appendix 1 );

2.4.7. p*

:

hydraulic pressure in the brake cylinder to produce the braking force B*;

2.4.8. p_T

:

test pressure according to point 6.2.1:

2.4.9. ρ′

:

characteristic of the brake when the towed vehicle moves forward as defined from:

M = ρ′ (p – p_o)

2.4.9.1. ρ′_r

:

characteristic of the brake when the towed vehicle moves rearward as defined from:

M_r = ρ′_r (p_r – p_or)

2.5. Symbols with respect to the braking requirements relating to overload protectors

2.5.1. D_op

:

application force at the input side of the control device, at which the overload protector is activated

2.5.2. M_op

:

brake torque at which the overload protector is activated (as declared by the manufacturer)

2.5.3. M_Top

:

minimum test braking torque in the case when an overload protector is fitted (according to point 6.2.2.2).

2.5.4. P_op_min

:

force applied to the brake at which the overload protector is activated (according to point 6.2.2.1).

2.5.5. P_op_max

:

maximum force (when the coupling head is pushed fully home) which is applied by the overload protector to the brake (according to point 6.2.2.3).

2.5.6. p_op_min

:

pressure applied to the brake at which the overload protector is activated (according to point 6.2.2.1).

2.5.7. p_op_max

:

maximum hydraulic pressure (when the coupling head is pushed fully home) which is applied by the overload protector to the brake actuator (according to point 6.2.2.3).

2.5.8. P_Top

:

minimum test brake force in the case when an overload protector is fitted (according to point 6.2.2.2).

2.5.9. p_Top

:

minimum test brake pressure in the case when an overload protector is fitted (according to point 6.2.2.2).

2.6 Types of vehicle classes with regard to inertia braking systems

2.6.1. Vehicle Class A

Vehicle Class A means vehicles of categories R1, R2 and S1

2.6.2. Vehicle Class B

Vehicle Class B means vehicles with a mass exceeding 3 500 kg and not exceeding 8 000 kg of categories R3 and S2

2.6.3. Vehicle Class C

Vehicle Class C1 means vehicles of categories R and S with maximum design speed not exceeding 30 km/h

Vehicle Class C2 means vehicles of categories R and S with maximum design speed not exceeding 40 km/h

Vehicle Class C3 means vehicles of categories R and S with maximum design speed exceeding 40 km/h

3. General requirements

3.1. The transmission of force from the coupling head to the towed vehicle's brakes shall be effected either by rod linkage or by one or more fluids. However, a sheathed cable (Bowden cable) may provide part of the transmission; this part shall be as short as possible. The control rods and cables shall not contact the towed vehicle frame or other surfaces that may affect the application or release of the brake.

3.2. All bolts at joints shall be adequately protected. In addition, these joints shall be either self-lubricating or readily accessible for lubrication.

3.3. Inertia braking devices shall be so arranged that in the case when the coupling head travels to its fullest extent, no part of the transmission seizes, undergoes permanent distortion, or breaks. This shall be checked by uncoupling the end of the transmission from the brake control levers.

3.4. The inertia braking system shall allow the towed vehicle to be reversed with the tractor without imposing a sustained drag force exceeding 0,08 g · G_A. Devices used for this purpose shall act automatically and disengage automatically when the towed vehicle moves forward.

3.5. Any special device incorporated for the purpose of point 3.4 shall be such that the parking performance when facing up a gradient shall not be adversely affected.

3.6. Inertia braking systems may incorporate overload protectors. They shall not be activated at a force of less than D_op = 1,2 · D* (when fitted at the control device) or at a force of less than P_op = 1,2 · P* or at a pressure of less than pop = 1,2 · p* (when fitted at the brake) where the force P* or the pressure p* corresponds to a braking force of B* = 0,5 · g · G_Bo (in the case of Classes C2 and C3 vehicles) and B* = 0,35 · g · G_Bo (in the case of Class C1 vehicles).

4. Requirements for control devices

4.1. The sliding members of the control device shall be long enough to enable the full travel to be used even when the towed vehicle is coupled.

4.2. The sliding members shall be protected by a bellows or some equivalent device. They shall either be lubricated or be constructed of self-lubricating materials. The surfaces in frictional contact shall be made of a material such that there is neither electrochemical torque nor any mechanical incompatibility liable to cause the sliding members to seize.

4.3. The stress threshold (K_A) of the control device shall be not less than 0,02 g · G′_A and not more than 0,04 g · G′_A. However, in the case of classes C1 and C2 vehicles the stress threshold (K_A) of the control device may be in the range between 0,01 g · G′_A and 0,04 g · G′_A.

4.4. The maximum insertion force D₁ shall not exceed 0,10 g · G′_A in rigid drawbar towed vehicles and centre-axle towed vehicles and 0,067 g · G′_A in multi-axled drawbar towed vehicles.

4.5. The maximum tractive force D₂ shall be not less than 0,1 g · G′_A and not more than 0,5 g · G′_A.

In the case of vehicles of class B, also the condition D₂ ≥ 1 750 N + 0,05 g · G′_A is permitted as long as D₂ ≤ 0,5 g · G′_A.

5. Tests and measurements to be carried out on the control devices

5.1. Control devices submitted to the Technical Service conducting the tests shall be checked for conformity with the requirements laid down in points 3 and 4.

5.2. The following shall be measured in respect of all types of brakes:

5.2.1.

Travel s and effective travel s′;

5.2.2.

Supplementary force K;

5.2.3.

Force threshold K_A;

5.2.4.

Insertion force D₁;

5.2.5.

Tractive force D₂.

5.3. In the case of mechanical-transmission inertia braking systems, the following should be determined:

5.3.1.

The reduction ratio i_Ho measured at the mid-travel position of the control;

5.3.2.

The control-device output force P′ as a function of the thrust D on the drawbar; the supplementary force K and the efficiency are derived from the representative curve obtained from these measurements

(see Figure 2 of Appendix 1).

5.4. In the case of hydraulic-transmission inertia braking systems, the following shall be determined:

5.4.1.

The reduction ratio i_h measured at the mid-travel position of the control device;

5.4.2.

The master cylinder output pressure p as a function of the thrust D on the drawbar and of the surface area F_HZ of the master-cylinder piston, as specified by the manufacturer; the supplementary force K and the efficiency are derived from the representative curve obtained from these measurements

(see Figure 3 of Appendix 1);

5.4.3.

The spare travel of the master cylinder s″, as referred to in point 2.2.19;

5.4.4.

Surface area F_HZ of the piston in the master cylinder;

5.4.5.

Stroke s_Hz of the master cylinder (in millimetres);

5.4.6.

Spare travel s″_Hz of the master cylinder (in millimetres).

5.5. In the case of inertia braking system on multi-axled drawbar towed vehicles, the loss of travel s_o referred to in the test report shall be measured.

6. Requirements for brakes

6.1. In addition to the brakes to be checked, the manufacturer shall submit to the Technical Service conducting the tests, drawings of the brakes showing the type, dimensions and material of the essential components and the make and type of the linings. In the case of hydraulic brakes, these drawings shall show the surface area F_RZ of the brake cylinders. The manufacturer shall also specify the braking torque M* and the mass G_Bo specified in point 2.2.4.

6.2. Testing conditions

6.2.1. In the case when an overload protector is neither fitted nor intended to be fitted within the inertia braking system, the wheel brake shall be tested with the following test forces or pressures:

P_T = 1,8 P* or p_T = 1,8 p* and M_T = 1,8 M* as appropriate.

6.2.2. In the case when an overload protector is fitted or intended to be fitted within the inertia braking system, the wheel brake shall be tested with the following test forces or pressures:

6.2.2.1.

The minimum design values for an overload protector shall be specified by the manufacturer and shall not be less than

P_op = 1,2 P* or p_op = 1,2 p*

6.2.2.2.

The ranges of minimum test force P_Top or minimum test pressure p_Top and the minimum test torque M_Top are:

P_Top = 1,1 to 1,2 P* or p_Top = 1,1 to 1,2 p*

and

M_Top = 1,1 to 1,2 M*

6.2.2.3.

The maximum values (P_op_max or p_op_max) for the overload protector shall be specified by the manufacturer and shall not be more than P_T or p_T respectively.

7. Tests and measurements to be carried out on the brakes

7.1. Brakes and components submitted to the Technical Service conducting the tests shall be tested for conformity with the requirements of point 6.

7.2. The following should be determined:

7.2.1.

The minimum brake-shoe lift (minimum brake-shoe application travel), 2s_B*;

7.2.2.

The brake-shoe centre lift (brake-shoe application travel) 2s_B (which shall be greater than 2s_B*);

7.3. In the case of mechanical brakes, the following shall be determined:

7.3.1.

Reduction ratio i_g (see Figure 4 of Appendix 1);

7.3.2.

Force P* for braking torque M*;

7.3.3.

Torque M* as a function of the force P* applied to the control lever in mechanical-transmission systems.

The rotational speed of the braking surfaces shall correspond to an initial vehicle speed of 30 km/h in the case of Class C1 vehicle, 40 km/h in the case of Class C2 vehicle, 60 km/h in the case of Class C3 vehicle, when the towed vehicle moves forward and 6 km/h when the towed vehicle moves rearward. The following shall be derived from the curve obtained from these measurements (see Figure 6 of Appendix 1):

7.3.3.1.

The brake-retraction force Po and the characteristic value ρ when the trailer moves forward;

7.3.3.2.

The brake-retraction force P_or and the characteristic value ρ_r when the towed vehicle moves rearward;

7.3.3.3.

Maximum braking torque M_r up to the maximum permissible travel s_r when the towed vehicle moves rearward (see Figure 6 of Appendix 1);

7.3.3.4.

Maximum permissible travel at the brake control lever when the towed vehicle moves rearward (see Figure 6 of Appendix 1).

7.4. In the case of hydraulic brakes, the following shall be determined:

7.4.1.

Reduction ratio i_g′ (see Figure 8 of Appendix 1)

7.4.2.

Pressure p* for braking torque M*

7.4.3.

Torque M* as a function of the pressure p* applied to the brake cylinder in hydraulic transmission systems.

The rotational speed of the braking surfaces shall correspond to an initial vehicle speed of 30 km/h in the case of Class C1 vehicle, 40 km/h in the case of Class C2 vehicle, 60 km/h in the case of Class C3 vehicle, when the towed vehicle moves forward and 6 km/h when the towed vehicle moves rearward. The following shall be derived from the curve obtained from these measurements (see Figure 7 of Appendix 1):

7.4.3.1.

The retraction pressure p_o and the characteristic ρ′ when the towed vehicle moves forward;

7.4.3.2.

The retraction pressure p_or and the characteristic ρ′_r when the towed vehicle moves rearward;

7.4.3.3.

Maximum braking torque M_r up to the maximum permissible fluid volume V_r when the towed vehicle moves rearward (see Figure 7 of Appendix 1);

7.4.3.4.

Maximum permissible fluid volume V_r absorbed by one braking wheel when the towed vehicle moves rearward (see Figure 7 of Appendix 1).

7.4.4.

Surface area F_RZ of the piston in the brake cylinder.

7.5. Alternative procedure for the Type-I test

7.5.1. The Type-I test according to Annex II, point 2.3 does not have to be carried out on a vehicle submitted for type approval, if the braking system components are tested on an inertia test bench to meet the prescriptions of Annex II, points 2.3.2 and 2.3.3.

7.5.2. The alternative procedure for the Type-I test shall be carried out in accordance with the provisions laid down in Annex VII, Appendix 1, point 3.5.2 (in analogy also applicable for disc brakes).

8. Simulated gradient parking braking system force differential

8.1. Calculation method

8.1.1. The pivot points in the compensator shall lie in a straight line with the park brake at the rest position.

Alternative arrangements can be used, if they provide equal tension in both rear cables, even when there are differences in travel between the rear cables.

8.1.2. Drawing details are to be provided to demonstrate that the compensator articulation is sufficient to ensure equal cable tension is applied to each of the rear cables. The compensator needs to have sufficient distance across the width to facilitate the differential travels left to right. The jaws of the yokes also need to be deep enough relative to their width to make sure that they do not prevent articulation when the compensator is at an angle.

Differential travel at compensator (s_cd) shall be derived from:

Where:

Sc′ = S′/iH	(travel at compensator — forward operation) and Sc′ = 2 · SB/ig
Scr = Sr/iH	(travel at compensator — rearward operation)

9. Test reports

Applications for the approval of towed vehicles equipped with inertia braking systems shall be accompanied by the test reports relating to the control device and the brakes and the test report on the compatibility of the inertia type control device, the transmission device and the brakes of the towed vehicle, these reports including at least the particulars prescribed on the basis of Article 27(1) of Regulation (EU) No 167/2013.

10. Compatibility between the control device and the brakes of a vehicle

10.1. A check shall be made on the vehicle to verify in the light of the characteristics of the control device, the characteristics of which are mentioned in the test report, the characteristics of the brakes mentioned in the test report and the towed vehicle characteristics referred to in the test report, whether the towed vehicle's inertia braking system meets the prescribed requirements.

10.2. General checks for all types of brakes

10.2.1. Any parts of the transmission not checked at the same time as the control device or the brakes shall be checked on the vehicle. The results of the check shall be entered in the test report (e.g., i_H1 and η_H1).

10.2.2. Mass

10.2.2.1. The maximum mass G_A of the towed vehicle shall not exceed the maximum mass G′_A for which the control device is authorised.

10.2.2.2. The maximum mass G_A of the towed vehicle shall not exceed the maximum mass G_B which can be braked by joint operation of all of the towed vehicle's brakes.

10.2.3. Forces

10.2.3.1. The force threshold K_A shall not be below 0,02 g · G_A and not above 0,04 g · G_A.

10.2.3.2. The maximum insertion force D₁ may not exceed 0,10 g · G_A in rigid drawbar towed vehicles and centre-axle towed vehicles and 0,067 g · G_A in multi-axled drawbar towed vehicles.

10.2.3.3. The maximum tractive force D₂ shall be between 0,1 g · G_A and 0,5 g · G_A.

10.3. Check of braking efficiency

10.3.1. The sum of the braking forces exerted on the circumference of the towed vehicle wheels shall not be less than B* = 0,50 g · GA (in the case of Classes C2 and C3 vehicles) and B* = 0,35 · g · G_A (in the case of Class C1 vehicles), including a rolling resistance of 0,01 g · GA: this corresponds to a braking force B of 0,49 g · GA (in the case of Classes C2 and C3 vehicles) and B* = 0,34 · g · G_A (in the case of Class C1 vehicles). In this case, the maximum permissible thrust on the coupling shall be:

• D* = 0,067 g · GA in the case of multi-axled drawbar towed vehicles;

  and

• D* = 0,10 g · GA in the case of rigid drawbar towed vehicles and centre-axle towed vehicles.

To check whether these conditions are complied with the following inequalities shall be applied:

10.3.1.1. In mechanical-transmission inertia braking systems:

10.3.1.2. In hydraulic-transmission inertia braking systems:

10.4. Check of control device travel

10.4.1. In control devices for multi-axled drawbar towed vehicles where the brake rod linkage depends on the position of the towing device, the control device travel s shall be longer than the effective (useful) control device travel s′, the difference being at least equivalent to the loss of travel s_o. The travel loss of s_o shall not exceed 10 per cent of the effective travel s′.

10.4.2. The effective (useful) travel of control device s′ shall be determined for single and multi-axle towed vehicles as follows:

10.4.2.1.

If the brake rod linkage is affected by the angular position of the towing device, then:

s′ = s – s_o

10.4.2.2.

If there is no loss of travel, then:

s′ = s

10.4.2.3.

In hydraulic braking systems:

s′ = s – s″

10.4.3. The following inequalities shall be applied to check whether control device travel is adequate;

10.4.3.1.

In mechanical-transmission inertia braking systems:

10.4.3.2.

in hydraulic-transmission inertia braking systems:

10.5. Additional checks

10.5.1. In mechanical-transmission inertia braking systems a check shall be made to verify that the rod linkage by which the forces are transmitted from the control device to the brakes is correctly fitted.

10.5.2. In hydraulic-transmission inertia braking systems a check shall be made to verify that the travel of the master cylinder is not less than s/i_h. A lower level shall not be permitted.

10.5.3. The general behaviour of the vehicle when braking shall be the subject of a road test carried out at different road speeds with different levels of brake effort and rates of application. Self-excited, undamped oscillations shall not be permitted.

11. General comments

The above requirements apply to the most usual embodiments of mechanical-transmission or hydraulic-transmission inertia braking systems where, in particular, all of the towed vehicle's wheels are equipped with the same type of brake and the same type of tyre. For checking less usual embodiments, the above requirements shall be adapted to the circumstances of the particular case.

Appendix 1 Explanatory diagrams

Figure 1

Symbols valid for all types of brakes

(See point 2.2 of this Annex)

Figure 2

Mechanical-transmission

(See points 2.2.10 and 5.3.2 of this Annex)

Figure 3

Hydraulic-transmission

(See points 2.2.10 and 5.4.2 of this Annex)

Figure 4

Brake checks

(See point 2.2.22 and 2.3.4 of this Annex)

Figure 5

Mechanical-transmission braking system

(See point 2.3 of this Annex)

Figure 5A

Mechanical-transmission braking system

(See point 2.3 of this Annex)

Figure 6

Mechanical Brake

(see point 2 of this Annex)

Figure 7

Hydraulic Brake

(See point 2 of this Annex)

Figure 8

Hydraulic-Transmission Braking System

(See point 2 of this Annex)

(1)

Points 2.3.10, 2.3.11 and 2.3.12 only apply to the parking braking system differential travel calculation method.