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Draft Minutes of the twelfth meeting of

the UN Task Force on Reverse Warning Sound issues

Task Force meeting

Thursday: 01 October from 9:30 am to 12:30 pm CET

Web conference

Friday: 02 October from 9:30 am to 12:30 pm CET

Web conference


  1. Welcome and introduction

Mr. Houzu as the Chair of this TF opened the 12 th meeting of TF on RWS and welcomed all participants.

Due to COVID-19 situation this meeting was again organized as a WebEx meeting.

All attendees agreed to share the information, which is available on the Attendance List, and to allow uploading the list to the UNECE Website (see TFRWS-12-07 )

  1. Adoption of the agenda

The Agenda (see TFRWS-12-01 ) was adopted with an additional agenda item under iv.

         Review of document TFRWS-12-02 Rev.1 , prepared by Japan, to improve the Draft proposal (see TFRWS-09-04 Rev.1 )

  1. Approval of the Minutes from 11 th Task Force meeting on Reverse Warning Sound

The Minutes of the 11 th meeting were approved (see TFRWS-11-05 )

  1. Confirming following items

         Analysis of the collected measurement data during the verification tests

Due to the current COVID-19 pandemic only one of OICA’s Task Force Experts, Daimler, was able to perform measurement in front of this meeting.

If the COVID-19 pandemic allows to conduct measurements, Renault and Scania are still willing to perform them. Volvo is not able to do so. Instead their Expert will look into the already existing measurement data, reanalyze them and present the result at the 13 th meeting. The Experts from Japan explained, that they have not planned to perform further measurements.

The Expert from Daimler presented the results of their measurement program (see TFRWS-12-03 ). The measurement test program was performed according to the protocol as shown in the Status report of the Task Force, presented at the 71 st session of GRBP (see Informal document GRBP-71-27-Rev.1 ).

The sound level of the background noise during these measurements was less than 40 dB(A) and the LAFmax 1/3 Octave band was always at 2.5 kHz.

The presented results were very much in line with the previous shown measurements by GREWUS ( TFRWS-11-02 Rev.1 ) and Japan ( TFRWS-11-03 ).

The Group discussed the measurement results and came to the conclusion that a device with tonal sound is much more sensitive than a device with broadband sound in regard to the microphone height above the ground due to ground reflection.

The Group agreed, that it makes no sense to repeat the test program according to the defined measurement protocol. A second validation program were approved.

The microphone shall be located at a distance of 7 meter behind the vehicle.

To define how many microphone positions behind the vehicle are needed, five microphone positions were chosen in 7 meter distance behind the vehicle. At these positions the microphones shall be located from 0.5 m to 1.6 m above the ground; distance between each microphone position shall be 10 cm. The additional measurement point at a height of 1.6 m was chosen to align the measurement program with the proposed new microphone positions by ISO to improve measurement variations and minimize measurement uncertainty in ISO 16254, which is the test procedure used UN Regulation No. 138.

See GRBP-70-09 :

“ISO/CD 16254

  1. Replace single microphone with array microphone.
  2. Report highest 1/3 octave band result within the array.
  3. Use “Max Hold” as 1/3 octave reporting method.


  • Reduce variation and improve repeatability and reproducibility.
  • Measurement results better correlated to human experience”

The measurement setup for this second validation program is shown in TFRWS-12-05 . OICA’s Experts will perform the promised measurements according to the measurement setup for the second validation program.

The Expert form China explained, that this approach is in line with their approach regarding the future development of UN Regulation No. 28 as presented in the Informal document GRB-63-17 at the 63 rd session of GRB in February 2016.


The Experts stressed out, that this second validation program is only used for finding the best way of measuring the sound pressure level emitted by the reverse warning device. After having analyzed the results, the aim is to simplify the test procedure as much as possible but still being able to “ Reduce variation and improve repeatability and reproducibility ”.

In relation to this validation program the Expert from Volvo will analyze the requirements of ISO9533:2010.

“ISO 9533:2010 specifies a static test method for determining the sound output performance and alarm activation requirements of audible travel alarms and forward horns mounted on earth-moving machinery, as defined in ISO 6165, for operation on work sites and travelling on public roads. It offers objective test methodologies and performance criteria.”

The Expert form CLEPA presented in addition a diagram as an example where recorded dB values using ISO9533 were shown (see TFRWS-12-04 ).


         Review of document TFRWS-12-02 Rev.1 , prepared by Japan, to improve the Draft proposal (see TFRWS-09-04 Rev.1 )

The Experts discussed the document and added decisions, agreement, comments or open issues to each paragraph, which the Task Force worked on during its 12 th meeting. These are summarized in document TFRWS-12-02 Rev.2 and marked in BLUE in column E.

In the comments in column E the Experts can also find their tasks they have promised to prepare for the 13 th meeting.


         Next steps

         Analysis of the collected measurement data during the verification tests according to TFRWS-12-05

         Continue the discussion on TFRWS-12-02 Rev.2


The aim of the Task Force is still to submit a Working document for the 73 rd session of GRBP in January 2021, having in mind that this will highly depend on the COVID-19 pandemic.


  1. Date and place of the next meeting

13 th meeting of TF on RWS issues :

  • Monday, 19 th October 2020 from 8 am to 11 am CET
  1. Other Business