Commission Delegated Regulation (EU) 2015/68 of 15 October 2014 supplementing Regulation (EU) No 167/2013 of the European Parliament and of the Council with regard to vehicle braking requirements for the approval of agricultural and forestry vehicles Text with EEA relevance

Appendix 2

Utilisation of adhesion

1. Method of measurement for tractors

1.1.1. The coefficient of adhesion (k) shall be determined as the quotient of the maximum braking forces without locking the wheels and the corresponding dynamic load on the axle being braked.

1.1.2. The brakes shall be applied only on one axle of the vehicle under test, at an initial speed of 50 km/h. The braking forces shall be distributed between the wheels of the axle to reach maximum performance. The anti-lock braking system shall be disconnected, or inoperative, between 40 km/h and 20 km/h.

1.1.4. The braking forces shall be calculated from the measured braking rate and the rolling resistance of the un-braked axle(s) which is equal to 0,015 and 0,010 of the static axle load for a driven axle and a non-driven axle, respectively.

1.1.5. The dynamic load on the axle shall be calculated from the braking rate, static axle load, wheelbase and centre of gravity height.

1.1.6. The value of k shall be rounded to three decimal places.

1.1.7. Then, the test shall be repeated for the other axles(s) as defined in points 1.1.1 to 1.1.6 (for exemptions, see points 1.4 and 1.5).

1.1.8. For example, in the case of a two-axle rear-wheel drive vehicle, with the front axle being braked, the coefficient of adhesion (k) is given by:

1.1.9. One coefficient shall be determined for the front axle kf and one for the rear axle kr.

1.2.1. The adhesion utilised (ε) is defined as the quotient of the maximum braking rate with the anti-lock braking system operative (zAL) and the coefficient of adhesion kM, i.e.

1.2.2. From an initial vehicle speed of 55 km/h, or vmax whichever is lower, the maximum value for the braking rate (zAL) shall be measured with full cycling of the anti-lock braking system. This value for zAL shall be based on the average value of three tests, as previously described in point 1.1.3, using the time taken for the speed to reduce from 45 km/h to 15 km/h, according to the following formula:

1.2.3. The coefficient of adhesion kM shall be determined by weighting with the dynamic axle loads: Where:

1.2.4. The value of ε shall be rounded to two decimal places.

1.2.5. In the case of a vehicle equipped with an anti-lock braking system of category 1 or 2, the value of zAL is based on the whole vehicle, with the anti-lock braking system in operation, and the adhesion utilised (ε) shall be given by the same formula quoted in point 1.2.1.

1.2.6. In the case of a vehicle equipped with an anti-lock braking system of category 3, the value of zAL shall be measured on each axle which has at least one directly controlled wheel. Example: for a two-axle vehicle with an anti-lock braking system acting only on the rear axle (2), the adhesion utilised (ε) is given by: This calculation shall be made for each axle having at least one directly controlled wheel.

1.3. If ε > 1,00, the measurements of coefficients of adhesion shall be repeated. A tolerance of 10 % is acceptable.

1.4. For tractors equipped with three axles, any axles that are interconnected by either suspension components and thereby react to weight transfer under braking or driveline may be disregarded in establishing a k value for the vehicle. Until a uniform test procedure is agreed, vehicles with more than three axles and special vehicles shall be subject to consultation with the technical service.

2. Method of measurement for towed vehicles

2.1.1. The coefficient of adhesion (k) shall be determined as the quotient of the maximum braking forces without locking the wheels and the corresponding dynamic load on the axle being braked.

2.1.2. The brakes shall be applied on only one axle of the towed vehicle under test, at an initial speed of 50 km/h. The braking forces shall be distributed between the wheels of the axle to reach maximum performance. The anti-lock braking system shall be disconnected or inoperative between 40 km/h and 20 km/h.

2.1.4. The adhesion utilised (ε) shall be calculated by means of the formula: The k value shall be determined according to point 2.2.3 for drawbar towed vehicles or point 2.3.1 for rigid drawbar towed vehicles and centre-axle towed vehicles, respectively.

2.1.5. If ε > 1,00 the measurements of coefficients of adhesion shall be repeated. A tolerance of 10 % is accepted.

2.1.6. The maximum braking rate (zRAL) shall be measured with full cycling of the anti-lock braking system and the tractor unbraked, based on the average value of three tests, as in point 2.1.3.

2.2.1. The measurement of k (with the anti-lock braking system being disconnected, or inoperative, between 40 km/h and 20 km/h) shall be performed for the front and rear axles. For one front axle i: For one rear axle i:

2.2.2. The values of kf and kr shall be rounded to three decimal places.

2.2.3. The coefficient of adhesion kR shall be determined proportionally according to the dynamic axle loads.

2.2.4. Measurement of zRAL (with the anti-lock braking system operative) zRAL shall be determined on a surface with a high coefficient of adhesion and, for vehicles with a category A anti-lock braking system, also on a surface with a low coefficient of adhesion.

2.3.1. The measurement of k (with the anti-lock braking system being disconnected, or inoperative, between 40 km/h and 20 km/h) shall be carried out with wheels fitted only on one axle, the wheels of the other axle(s) are removed.

2.3.2. The measurement of zRAL (with the anti-lock braking system operative) shall be carried out with all wheels fitted. zRAL shall be determined on a surface with a high coefficient of adhesion and, for vehicles with a category A anti-lock braking system, also on a surface with a low coefficient of adhesion.

Appendix 3

Performance on differing adhesion surfaces

1. Tractors

1.1. The prescribed braking rate referred to in point 5.3.5 of this Annex may be calculated by reference to the measured coefficient of adhesion of the two surfaces on which this test is carried out. The two surfaces shall satisfy the conditions set out in point 5.3.4. of this Annex.

1.2. The coefficient of adhesion (kH and kL) of the high- and low-adhesion surfaces, respectively, shall be determined in accordance with the provisions in point 1.1 of Appendix 2.

1.3. The braking rate (zMALS) for laden tractors shall be:

2. Towed vehicles

2.1. The braking rate referred to in point 6.3.2 of this Annex may be calculated by reference to the measured braking rates zRALH and zRALL on the two surfaces on which the tests are carried out with the anti-lock braking system operative. These two surfaces shall satisfy the conditions prescribed in point 6.3.2 of this Annex.

2.2. The braking rate zRALS shall be: If εΗ > 0,95 use εΗ = 0,95.

Appendix 4

Method of selection of the low-adhesion surface

ANNEX XII

Requirements applying to EBS of vehicles with compressed-air braking systems or of vehicles with data communication via pin 6 and 7 of ISO 7638 connector and to vehicles fitted with such EBS

1. Definitions

For the purposes of this Annex:

1.1. ‘point-to-point’ means a topology of a communication network with only two units. Each unit has an integrated termination resistor for the communication line;

1.2. ‘braking signal’ means a logic signal indicating brake activation.

2. General requirements

2.1. The electric control line shall conform to ISO 11992-1 and 11992-2:2003 including Amd.1:2007 and be a point-to-point type using the seven pin connector according to ISO 7638-1 or 7638-2:2003. The data contacts of the ISO 7638 connector shall be used to transfer information exclusively for braking (including ABS) and running gear (steering, tyres and suspension) functions as specified in ISO 11992-2:2003 including Amd.1:2007. The braking functions have priority and shall be maintained in the normal and failed modes. The transmission of running gear information shall not delay braking functions. The power supply, provided by the ISO 7638 connector, shall be used exclusively for braking and running gear functions and that required for the transfer of towed vehicle related information not transmitted via the electric control line. However, in all cases the provisions of point 5.2.1 shall apply. The power supply for all other functions shall use other measures.

2.2. The support of messages defined within ISO 11992-2:2003 including Amd.1:2007 is specified in Appendix 1 to this Annex for the tractor and towed vehicle as appropriate.

2.3. The functional compatibility of tractors and towed vehicles equipped with electric control lines shall be assessed at the time of type approval by checking that the relevant provisions of ISO 11992:2003, including ISO 11992-2:2003 and its Amd.1:2007 parts 1 and 2, are fulfilled. Appendix 2 to this Annex provides an example of tests that may be used to perform this assessment.

2.4. When a tractor is equipped with an electric control line and electrically connected to a towed vehicle equipped with an electric control line, a continuous failure (> 40 ms) within the electric control line shall be detected in the tractor and shall be signalled to the driver by the yellow warning signal specified in point 2.2.1.29.1.2 of Annex I, when such vehicles are connected via the electric control line.

3. Special requirements for the connections between tractors and towed vehicles for compressed-air braking systems

3.1. The electric control line of the tractor shall provide information as to whether the requirements of point 2.2.1.16.3 of Annex I can be satisfied by the electric control line, without assistance from the pneumatic control line. It shall also provide information as to whether it is equipped according to point 2.1.4.1.2 of Annex I with two control lines or according to point 2.1.4.1.3 of Annex I with only an electric control line.

3.2. A tractor equipped according to point 2.1.4.1.3 of Annex I shall recognise that the coupling of a towed vehicle equipped according to point 2.1.4.1.1 of Annex I is not compatible. When such vehicles are electrically connected via the electric control line of the tractor, the driver shall be warned by the red optical warning signal specified in point 2.2.1.29.1.1 of Annex I and when the system is energised, the brakes on the tractor shall be automatically applied. This brake application shall provide at least the prescribed parking braking performance required by points 3.1.3.1 and 3.1.3.2 of Annex II respectively.

3.3. In the case of a tractor equipped with two control lines as described in point 2.1.4.1.2 of Annex I, when electrically connected to a towed vehicle which is also equipped with two control lines, all of the following conditions shall be fulfilled:

3.4. A towed vehicle may be equipped as described in point 2.1.4.1.3 of Annex I, provided that it can only be operated in conjunction with a tractor with an electric control line which satisfies the requirements of point 2.2.1.16.3 of Annex I. In any other case, the towed vehicle, when electrically connected, shall automatically apply the brakes or remain braked. The driver shall be warned by the separate yellow warning signal specified in point 2.2.1.29.2 of Annex I.

3.5. If the operation of the parking braking system on the tractor also operates a braking system on the towed vehicle, as permitted by point 2.1.2.3 of Annex I, then the following additional requirements shall be met:

4. Special additional requirements for service braking systems with electric control transmission

4.1.1. With the parking braking system released, the service braking system shall be able to generate a static total braking force at least equivalent to that required by the prescribed Type-0 test, even when the ignition/start switch has been switched off and/or the key has been removed. In the case of tractors authorised to tow vehicles of category R3b or R4b, such vehicles shall provide a full control signal for the service braking system of the towed vehicle. It should be understood that sufficient energy is available in the energy transmission of the service braking system.

4.1.2. In the case of a single temporary failure (< 40 ms) within the electric control transmission, excluding its energy supply, (e.g. non-transmitted signal or data error) there shall be no distinguishable effect on the service braking performance.

4.1.3. A failure within the electric control transmission, not including its energy reserve, that affects the function and performance of systems addressed in this Regulation shall be indicated to the driver by the red or yellow warning signal specified in points 2.2.1.29.1.1 and 2.2.1.29.1.2 of Annex I, respectively, as appropriate.  When the prescribed service braking performance can no longer be achieved (red warning signal), failures resulting from a loss of electrical continuity (e.g. breakage, disconnection) shall be signalled to the driver as soon as they occur, and the prescribed residual braking performance shall be fulfilled by operating the service braking control device in accordance with point 3.1.4 of Annex II. The manufacturer shall provide the Technical Service with an analysis of potential failures within the control transmission and their effects. This information shall be subject to discussion and agreement between the Technical Service and the vehicle manufacturer. These requirements shall not be construed as a departure from the requirements concerning secondary braking.

4.1.4. A tractor electrically connected to a towed vehicle via an electric control line, shall provide a clear warning to the driver whenever the towed vehicle provides the failure information that the stored energy in any part of the service braking system on the towed vehicle falls below the warning level, as specified in point 5.2.4. A similar warning shall also be provided when a continuous failure (> 40 ms) within the electric control transmission of the towed vehicle, excluding its energy reserve, precludes achievement of the prescribed service braking performance of the towed vehicle, as specified in point 4.2.3. The warning signal specified in point 2.2.1.29.2.1 of Annex I shall be used for this purpose.

4.1.5. In the event of a failure of the energy source of the electric control transmission, starting from the nominal value of the energy level, the full control range of the service braking system shall be guaranteed after twenty consecutive full stroke actuations of the service braking control device. During the test, the braking control device shall be fully applied for 20 seconds and released for 5 seconds on each actuation. It should be understood that during the above test, sufficient energy is available in the energy transmission to ensure full actuation of the service braking system. This requirement shall not be construed as a departure from the requirements of Annex IV.

4.1.6. When the battery voltage falls below a value nominated by the manufacturer at which the prescribed service braking performance can no longer be guaranteed and/or which precludes at least two independent service braking circuits from each achieving the prescribed secondary or residual braking performance, the warning signal specified in point 2.2.1.29.1.1 of Annex I shall be activated. After the warning signal has been activated, it shall be possible to apply the service braking control device and obtain at least the performances prescribed for residual and secondary braking in the case of tractor with maximum design speed exceeding 60 km/h or the performance prescribed for secondary braking in the case of tractor with maximum design speed not exceeding 60 km/h. It should be understood that sufficient energy is available in the energy transmission of the service braking system. This requirement shall not be construed as a departure from the requirement concerning secondary braking.

4.1.7. If auxiliary equipment is supplied with energy from the same reserve as the electric control transmission, it shall be ensured that, with the engine running at a speed not greater than 80 % of the maximum power speed, the supply of energy is sufficient to fulfil the prescribed deceleration values by either provision of an energy supply which is able to prevent discharge of this reserve when all auxiliary equipment is functioning or by automatically switching off pre-selected parts of the auxiliary equipment at a voltage above the critical level referred to in point 4.1.6 such that further discharge of this reserve is prevented. Compliance may be demonstrated by calculation or by a practical test. For vehicles authorised to tow a vehicle of category R3b or R4b the energy consumption of the towed vehicle shall be taken into account by a load of 400 W. This point does not apply to vehicles where the prescribed deceleration values can be reached without the use of electrical energy.

4.1.9. In the case of a failure in the electric control transmission of the service braking system of a tractor equipped with an electric control line according to point 2.1.4.1.2 or 2.1.4.1.3 of Annex I, the full actuation of the brakes of the towed vehicle shall remain ensured.

4.1.10. In the case of a failure in the electric control transmission of a towed vehicle, electrically connected via an electric control line only, according to point 2.1.4.1.3 of Annex I, braking of the towed vehicle shall be ensured according to point 2.2.1.17.2.1 of Annex I. This shall be the case whenever the towed vehicle provides the ‘supply line braking request’ signal via the data communication part of the electric control line or in the event of the continuous absence of this data communication. This point shall not apply to tractors which cannot be operated with towed vehicles connected via an electric control line only, as described in point 3.4.

4.2.1. In the case of a single temporary failure (< 40 ms) within the electric control transmission, excluding its energy supply, (e.g. non-transmitted signal or data error) there shall be no distinguishable effect on the service braking performance.

4.2.2. In the case of a failure within the electric control transmission (e.g. breakage, disconnection), of at least 30 % of the prescribed performance for the service braking system of the relevant towed vehicle shall be maintained. Until uniform test procedures have been agreed, the manufacturer shall provide the Technical Service with an analysis of potential failures within the control transmission, and their effects. This information shall be subject to discussion and agreement between the Technical Service and the vehicle manufacturer. For towed vehicles, electrically connected via an electric control line only, according to point 2.1.4.1.3 of Annex I, and fulfilling the requirements set out in point 2.2.1.17.2.2 of Annex I with the performance prescribed in point 3.2.3 of Annex II, it is sufficient that the provisions of point 4.1.10 of this Annex are invoked, when a braking performance of at least 30 % of the prescribed performance for the service braking system of the towed vehicle can no longer be ensured, by either providing the ‘supply line braking request’ signal via the data communication part of the electric control line or by the continuous absence of this data communication.

4.2.3. A failure within the electric control transmission of the towed vehicle that affects the function and performance of systems addressed by this Regulation and failures of energy supply available from the ISO 7638:2003 connector shall be indicated to the driver by the separate warning signal specified in point 2.2.1.29.2 of Annex I via pin 5 of the electrical connector conforming to ISO 7638:2003. In addition, towed vehicles equipped with an electric control line, when electrically connected to a tractor with an electric control line, shall provide the failure information for activation of the warning signal specified in point 2.2.1.29.2.1 of Annex I via the data communication part of the electric control line, when the prescribed service braking performance of the towed vehicle can no longer be ensured. However, in the case of any failure of the energy supply available from the ISO 7638:2003 connector, the indication of the yellow warning signal via pin 5 of the electrical connector conforming to ISO 7638:2003 is sufficient under the condition that the full braking force is still available.

5. Additional requirements

5.1.1.1. Activation of the service braking system by the driver shall generate a signal that will be used to illuminate the stop lamps.

5.1.1.3. In the case of vehicles equipped with a braking system of a specification different to that laid down in point 5.1.1.2, the operation of the endurance braking system may generate the signal irrespective of the deceleration produced.

5.1.1.4. The signal shall not be generated when deceleration is produced by the natural braking effect of the engine alone.

5.1.1.5. Activation of the service braking system by automatically commanded braking shall generate the signal mentioned above. However, when the deceleration generated is less than 0,7 m/s², the signal may be suppressed At the time of type approval, compliance with this requirement shall be confirmed by the vehicle manufacturer.

5.1.1.6. Activation of part of the service braking system by selective braking shall not generate the signal mentioned above. During a selective braking event, the function may change to automatically commanded braking.

5.1.1.7. In the case of vehicles equipped with an electric control line the signal shall be generated by the tractor when a message ‘illuminate stop lamps’ is received via the electric control line from the towed vehicle.

5.2.1. Whenever power supplied by the ISO 7638:2003 connector is used for the functions referred to in point 2.1, the braking system shall have priority and be protected from an overload external to the braking system. This protection shall be a function of the braking system.

5.2.2. In the case of a failure in one of the control lines connecting two vehicles equipped according to point 2.1.4.1.2 of Annex I the towed vehicle shall use the control line not affected by the failure to ensure, automatically, the braking performance prescribed for the towed vehicle in point 3.2.1 of Annex II.

5.2.3. When the supply voltage to the towed vehicle falls below a value nominated by the manufacturer at which the prescribed service braking performance can no longer be guaranteed, the separate yellow warning signal specified in point 2.2.1.29.2 of Annex I shall be activated via pin 5 of the ISO 7638:2003 connector. In addition, towed vehicles equipped with an electrical control line, when electrically connected to a tractor with an electric control line, shall provide the failure information for actuation of the warning signal specified in point 2.2.1.29.2.1 of Annex I via the data communication part of the electric control line.

6. Suppression of automatic braking

In the case of towed vehicles equipped with an electric control line and electrically connected to a tractor with an electric control line the automatic braking action specified in point 2.2.1.17.2.2 of Annex I may be suppressed as long as the pressure in the compressed air reservoirs of the towed vehicle is sufficient to ensure the braking performance specified in point 3.2.3 of Annex II.

Appendix 1

Compatibility between tractors and towed vehicles with respect to ISO 11992 data communications

1. General

1.1. The requirements of this Appendix shall only apply to tractors and towed vehicles equipped with an electric control line.

1.2. The ISO 7638 connector provides a power supply for the braking system or anti-lock braking system of the towed vehicle. In the case of vehicles equipped with an electric control line this connector also provides a data communication interface via Pins 6 and 7 as in point 2.1 of this Annex.

1.3. This Appendix lays down requirements applicable to the tractor and towed vehicle with respect to the support of messages defined within ISO 11992-2:2003 including Amd.1:2007.

Appendix 2

Test procedure to assess the functional compatibility of vehicles equipped with electric control lines

1. General

1.1. This Appendix lays down a procedure that may be used by the Technical Service to check tractors and towed vehicles equipped with an electric control line against the functional and performance requirements referred to in point 2.2. of Annex XII.

1.2. The references to ISO 7638 within this Appendix apply to ISO 7638-1:2003 for 24V applications and ISO 7638-2:2003 for 12V applications.

2. Tractors

The simulator shall:

2.1.1. Have a connector meeting ISO 7638:2003 (7 pin) to connect to the vehicle under test. Pins 6 and 7 of the connector shall be used to transmit and receive messages complying with ISO 11992:2003 including ISO 11992-2:2003 and its Amd.1:2007;

2.1.2. Be capable of receiving all of the messages transmitted by the motor vehicle to be type approved and be capable of transmitting all towed vehicle messages defined within ISO 11992-2:2003 and its Amd.1:2007;

2.1.3. Provide a direct or indirect readout of messages, with the parameters in the data field shown in the correct order relative to time; and

2.1.4. Include a facility to measure coupling head response time in accordance with point 2.6 of Annex III.

2.2.1. Confirm that the manufacturer's/supplier's information document demonstrates compliance with the provisions of ISO 11992 with respect to the physical layer, data link layer and application layer.

3. Towed vehicles

The simulator shall:

3.1.1. Have a connector meeting ISO 7638:2003 (7 pin) to connect to the vehicle under test. Pins 6 and 7 of the connector shall be used to transmit and receive messages complying with ISO 11992:2003 including ISO 11992-2:2003 and its Amd.1:2007;

3.1.2. Have a failure warning display and an electrical power supply for the towed vehicle;

3.1.3. Shall be capable of receiving all of the messages transmitted by the towed vehicle to be type approved and be capable of transmitting all motor vehicle messages defined within ISO 11992-2:2003 and its Amd.1:2007.

3.1.4. Provide a direct or indirect readout of messages with the parameters in the data field shown in the correct order relative to time; and

3.1.5. Include a facility to measure brake system response time in accordance with point 4.5.2 of Annex III.

3.2.1. Confirm that the manufacturer's or supplier's Information Document, demonstrates compliance with the provisions of ISO 11992:2003 including ISO 11992-2:2003 and its Amd.1:2007 with respect to the physical layer, data link layer and application layer.

ANNEX XIII

Requirements applying to hydraulic braking systems capable of hydraulic connections of the single-line type

1. General

1.1. The hydraulic control line of the tractor referred to in point 2.1.5.1.1. of Annex I may operate as a hydraulic connection of the single-line type provided that the pressures generated on the connector comply with points 1.1.1, 1.1.2 and 1.1.3.

1.3. The service braking system of the tractor shall be fitted with a device so designed that if the towed vehicle braking system should fail, or the control line between the tractor and towed vehicle should break, it will still be possible to brake the tractor with the effectiveness prescribed for the secondary braking system in this Regulation.

2. Hydraulic connections of the single-line type between tractors and towed vehicles equipped with hydraulic braking systems shall fulfil the following requirements:

2.1. Type of connection: hydraulic control line with the male connector on the tractor and the female connector on the towed vehicle. The connectors shall comply with ISO 5676:1983.

2.2. With the engine running and the control device of the service braking system of the tractor fully applied a pressure between 10 000 kPa and 15 000 kPa shall be generated on the control line.

2.3. With the engine running and no brake control device on the tractor applied (driving or stand-by condition), the pressure supplied at the coupling head of the control line shall be 0⁺²⁰⁰ kPa.

2.4. The response time requirements of Annex III do not apply to this type of connection.

2.5. The compatibility requirements according to Appendix 1 to Annex II do not apply to this type of connection.

3. Alternative requirements

As an alternative to the requirements of sections 1 and 2, hydraulic connection of the single line type installed on tractors shall fulfil all the requirements of this section, in addition to the provisions of point 2.1.

3.1. The hydraulic circuit shall be provided with a relief valve to prevent hydraulic pressures exceeding 15 000 kPa.

3.2. With no brake control device (including parking brake) applied on the tractor, at any engine revolutions per minute (RPM) between low idle and rated speed, pressure at coupling head shall be between 1 000 and 1 500 kPa.

3.3. Applying tractor service brakes gradually, pressure at coupling head shall increase progressively and reach the maximum specified value, which shall be between 12 000 and 14 000 kPa. Requirement shall be fulfilled at any engine RPM, as described in point 3.2.

3.4. Permissible relationship between braking rate TM/FM and the coupling head pressure pm shall be lower than line AAA of Figure 1. Requirement shall be fulfilled by the unladen vehicle.

3.5. The response time at the coupling head, measured connecting the towed vehicle simulator (as described in point 3.10) to the tractor, shall not be higher than 0,6 seconds. The response time shall be measured at the coupling head, starting from the moment of the pedal actuation until the moment when pressure reaches the value of 7 500 kPa. During the test, engine RPM shall be set to 2/3 of the rated speed. The ambient and vehicle temperature shall be stabilised between 10 °C and 30 °C. The pedal actuation time necessary to reach a pressure of 10 000 kPa at the coupling head, shall be not less than 0,2 seconds.

3.6. In case of failure of the towed vehicle braking system part, located on the tractor side, a pressure drop to 0 kPa (measured at the coupling head) shall be generated within 1 second, in order to apply the brakes of the towed vehicle. The same provision applies in case of shut off or low efficiency of the energy source.

3.7. In case of failure of the tractor service brakes, operator shall be able to drop the pressure at the coupling head to 0 kPa. This requirement may be achieved by an auxiliary manual control device.

3.8. The tractor shall be equipped with the warning signal specified in point 2.2.1.29.1.1 of Annex I; it shall be activated when the pressure in the towed vehicle braking system drops below 1 000 ^{(+0 – 200)} kPa.

3.9. Braking valve and energy source shall be marked in accordance with the requirements laid down in Article 24 of Delegated Regulation (EU) 2015/208.