UN R41 Base text (06 series) · UNECE Regulation No. 41 (ECE R41) — Uniform provisions concerning the approval of motorcycles with regard to noise.
UN R41 — 06 series of amendments
Changes from 05 series of amendments (supplement 3)
- What changed
- For nPP' ≥ nwot,(i), the RD-ASEP limit of Annex 7 is now the lower of the old line and a new logarithmic line.
- For vehicles tested in non-locked gear ratios, the maximum engine speed of the RD-ASEP control range is now S instead of 0.8 x S.
- The transitional provisions in paragraphs 12.2. to 12.4. now use the dates 1 January 2029 and 1 January 2030.
- Why
- IWG RD-ASEP proposed this series to strengthen the RD-ASEP testing conditions of motorcycles.
- The limit line for nPP’ > nwot,(i) is updated to reflect the technical progress since the 04 series first introduced it in 2011.
- To avoid legal uncertainty, GRBP asked the secretariat to include the draft Supplement 4 to the 05 series in the proposal.
Q1What changed60 changes
New RD-ASEP limit for nPP' ≥ nwot,(i) (Annex 7, para. 2.6.)
For nPP' ≥ nwot,(i), the limit is now the lower of two lines: the old line and a new line with a natural logarithm. The new line uses nAA’,min, nBB’,max and a new factor nadj. The factor nadj is the smaller of e^((S – nidle) / (nBB’ ,max – nwot,(i))) and 250. Before this series, the limit for nPP' ≥ nwot,(i) was only Lwot,(i) + (5 * (nPP' – nwot,(i)) / 1,000) + 3. The limit line for nPP' < nwot,(i) does not change. The symbols table of paragraph 2.13. adds nAA’,min, nBB’,max and nadj.
RD-ASEP control range and reference points (Annex 7, paras. 2.5. and 3.2.2.; Annex 1, item 18)
The minimum engine speed at line AA’ keeps the value 0,1 * (S – nidle) + nidle, but it now has the symbol nAA',min. The maximum engine speed nBB',max is 0,8 × S for vehicles tested in locked gears and S for vehicles tested in non-locked gear ratios. Before this series, item (d) of paragraph 2.5. said that nBB' must not exceed 0.8 x S. Item (b) of paragraph 3.2.2. now uses nBB' = nBB’,max instead of nBB' = 0.8 x S. In the table of Annex 1, item 18, the reference points are now (a) and (b) instead of (i) and (ii). The note under that table now starts with “Note:” instead of “Footnote:”.
Speed tolerances and deceleration (Annex 7, paras. 2.8. and 3.3.1.)
New paragraph 2.8. gives a tolerance of +/- 5km/h for the tests of paragraph 3.3. and of item (b) of paragraph 3.2.2. The tolerance applies inside the boundaries of the RD-ASEP control range. Paragraph 2.8. also gives examples for vBB’ and for vtest. Paragraph 3.3.1. no longer gives the +/- 5 km/h tolerance for vtest in its own text. Paragraph 3.3.1. now says when a deceleration is present: vPP’ < vAA’ - 5km/h, or vBB’ < vAA’ - 5km/h, or vBB’ < vPP’ - 5km/h. The values of the RD-ASEP control range are absolute values, and the tolerance of paragraph 2.8. must not increase or lower them.
User selectable programs or modes (Annex 3, para. 1.3.3.1.3.; Annex 7, paras. 2.6. and 3.3.2.)
New paragraph 1.3.3.1.3. of Annex 3 applies if the vehicle has user selectable software programs or modes. Then the test must be done in a mode that does not restrict the vehicle’s power performance and that produces the highest Lwot(i). The technical service selects the program or mode, based on manufacturer documentation. If Lwot(i) and nwot(i) are measured again for the RD-ASEP check, the same user selectable drive mode as in type approval must be used. Within the total number of paragraph 3.1., the additional operating conditions may use any available user selectable software program or mode. Before this series, that text named only programs or modes which affect the sound emissions of the vehicle.
Number of operating conditions and the role of the technical service (Annex 7, paras. 3.1., 3.3.1. and 3.3.2.)
For manual transmissions, the total of operating conditions for paragraph 3.3. starts from the number of gears multiplied by 3. For variable gear ratios or automatic transmission with non-lockable gear ratios, the total starts from 6. Both totals are then reduced by the conditions used for paragraph 3.2 tests and for the determination of Lurb. A minimum of 3 operating conditions must be tested according to paragraph 3.3. The conditions of paragraph 3.3.2. must now be defined by the technical service. Before this series, they may be defined by the technical service in agreement with the type approval authorities.
Test defeat and conformity of production (paras. 6.3.1. and 8.4.)
The prohibition covers a device, procedure or software which would modify noise related functional parameters of the vehicle for the purpose of passing the tests. It applies only if this would result in increased noise emissions during typical on-road operation in the RD-ASEP control range, compared to during testing. Before this series, the manufacturer must not intentionally alter, adjust, or introduce any device or procedure solely to fulfil the noise emission requirements. That old text applied to a device or procedure which will not be operational during typical on-road operation. New paragraph 8.4. applies if substantially different barometric pressure, humidity, temperature or rider mass prevents reaching awot,ref with the same gear as in type approval. Then, in conformity of production tests, the gear selection requirement of paragraph 1.3.3.3.1.3.1. of Annex 3 prevails, and the acceleration can differ from awot,ref.
Transitional provisions (paras. 12.1. to 12.6. and 12.9.)
From the official date of entry into force of the 06 series, Contracting Parties may not refuse to grant or accept 06 series approvals. From 1 January 2029, Contracting Parties are not obliged to accept approvals to the preceding series first issued after 1 January 2029. Until 1 January 2030, they must accept approvals to the preceding series first issued before 1 January 2029. From 1 January 2030, they are not obliged to accept approvals to the preceding series. Under paragraph 12.6., they must continue to accept such approvals for vehicles or vehicle systems not affected by the changes of the 06 series. Paragraph 12.9. now uses fixed dates: ISO 10844:2021 is accepted from 10 January 2025, and ISO 10844:2014 until 10 January 2030.
Q2Why it changed
- Proposed by
- Experts from the Informal Working Group on Real Driving - Additional Sound Emission Provisions (IWG RD-ASEP) and experts from the International Motorcycle Manufacturer Association (IMMA)
- Working party
- GRBP, 81st session (February 2025)
Reasons
The 05 series kept the RD-ASEP limit line of the 04 series, and its review was left for a later stage. This proposal updates the limit line for nPP’ > nwot,(i) to reflect the technical progress since 2011, when the 04 series first introduced it. The aim was to better reflect the natural sound emission behaviour of a motorcycle, and also to consider citizen complaints about too high motorcycle noise.
Sources (3)
“the RD-ASEP limit line was carried over from the 04 series of amendments, and a review of the RD-ASEP limit line would be addressed at a later stage.”
“The objective of this proposal is to update the limit line for nPP’ > nwot,(i) to reflect the technical progress since it was first introduced in the 04 series of amendments to UN Regulation No. 41, in 2011.”
“The aim was to better reflect the “natural sound emission behaviour” of a motorcycle (“natural” means without flexibilities in the exhaust/silencer system) while also considering citizen complaints from too high motorcycle noise.”
The new line is a ‘best fit’ line based on data from non-offending vehicles (vehicles without flaps). It reduces the available margin, especially at high engine speeds. The “min-function” guarantees that the revised limit is at no point higher than the limit of the 05 series.
Sources (3)
“A ‘best fit’ limit line was developed based on non-offending vehicle fleet data (vehicles without flaps)”
“while also reducing the available margin, especially at high engine speeds.”
“By applying the “min-function” to the formula, it is guaranteed that the revised RD-ASEP limit is at no point exceeding the current RD-ASEP limit (of the 05 series of amendments).”
Some vehicles with non-lockable Continuously Variable Transmissions (CVT) often exceeded the RD-ASEP engine speed control window, and the test runs were invalid. With these transmissions, such engine speeds are also more accessible in real-life conditions. To reflect real driving conditions better, IWG RD-ASEP decided to increase the engine speed control window for these vehicles.
Sources (3)
“some vehicles with non-lockable, Continuously Variable Transmissions (CVT) often exceeded the RD-ASEP engine speed control window during the RD-ASEP tests, resulting in invalid test runs.”
“Due to the nature of those transmissions, such engine speeds are also more accessible in real-life conditions.”
“To reflect better real driving conditions, the IWG RD-ASEP decided to increase the engine speed control window for those vehicles.”
IMMA noticed that technical services and type approval authorities had varying interpretations of the Annex 7 ASEP tests of the 05 series. These were about user selectable riding modes, the number of additional operating conditions and speed tolerances. IWG RD-ASEP wanted to clarify the original intent of the 05 series and to make sure that the ASEP tests are applied uniformly.
Sources (2)
“Technical Services and Type Approval Authorities had varying interpretations on how to test different user selectable riding modes, on how to determine the number of additional operating conditions and on which speed tolerances to apply”
“With this amendment proposal IWG RD-ASEP would like to clarify the original intent of the 05 series of amendments as well as to ensure uniform application of the ASEP tests.”
IMMA proposed changes to strengthen the provisions against test defeating, to facilitate conformity of production testing and to correct the communication document. New paragraph 8.4. is about conformity of production tests. Meteorological variables such as humidity and barometric pressure can change vehicle performance, and UN Regulation No. 41 does not consider them. The table in Annex 1 used (i) and (ii) for the reference points, while paragraph 3.2.2. of Annex 7 uses (a) and (b).
Sources (4)
“in order to strengthen provisions against test defeating, to facilitate the Conformity of Production testing and to correct the communication document.”
“The new paragraph 8.4. is addressing the Conformity of Production (CoP) tests.”
“Meteorological variables such as humidity and barometric pressure can result in variations of vehicle performance and are not considered by UN Regulation No. 41.”
“refers to the reference points as (i) and (ii), while the text in paragraph 3.2.2. of Annex 7 refers to those as (a) and (b).”
Document trail
- 2024-12ProposalECE/TRANS/WP.29/GRBP/2025/4Proposal by IWG RD-ASEP for a supplement to the 05 series
- 2024-12ProposalECE/TRANS/WP.29/GRBP/2025/5Proposal by IWG RD-ASEP for a new 06 series
- 2024-12ProposalECE/TRANS/WP.29/GRBP/2025/7Proposal by IMMA for a supplement to the 05 series
- —RevisedGRBP-81-02Revised 06 series proposal that replaces GRBP/2025/5
- —RevisedGRBP-81-03Revised supplement proposal that replaces GRBP/2025/4
- —Amended in sessionGRBP-81-15IMMA amendment to GRBP-81-02 for Annex 7, paragraph 2.5.
- —RevisedGRBP-81-29Revised IMMA proposal that replaces GRBP/2025/7
- —Working party adoptsECE/TRANS/WP.29/GRBP/79Session report, para. 6
- 2025-04Sent to WP.29ECE/TRANS/WP.29/2025/66Text that GRBP sent to WP.29 and AC.1
- 2025-06WP.29 adoptsECE/TRANS/WP.29/1186Adopted at the 196th session (session report, para. 111)
- 2026-01-11In forceC.N.23.2026.TREATIES-XI.B.16.41UN depositary notification
Q3Who is affected
Vehicle manufacturer
- Calculate the RD-ASEP limit for nPP' ≥ nwot,(i) with the new min function and the factor nadj.
- Check your vehicles against the new RD-ASEP limit for nPP' ≥ nwot,(i).
- Use nBB',max = S for vehicles tested in non-locked gear ratios, and 0,8 × S for vehicles tested in locked gears.
- Prepare documentation of your user selectable programs or modes for the technical service (paragraph 1.3.3.1.3.).
- Compare your devices, procedures and software that change noise related functional parameters with the new paragraph 6.3.1.
Component supplier
- Compare your devices and software that change noise related functional parameters with the new paragraph 6.3.1.
Technical service / Approval authority
- If a vehicle has user selectable programs or modes, select the one to test from the manufacturer documentation (paragraph 1.3.3.1.3.).
- Define the conditions for test speed, gear and mode selection and throttle operation.
- Apply the +/- 5km/h tolerance to paragraph 3.3. tests and item (b) of paragraph 3.2.2., within the RD-ASEP control range.
- Count the operating conditions for paragraph 3.3. with the new rules, with a minimum of 3.
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ⓘ This report gives advice only. It is not legal or type-approval advice.
More UN R41 change reports
- 06 series — Supplement 1
- 05 series — Supplement 5
- 05 series — Supplement 4
- 05 series — Supplement 3
- 05 series — Supplement 2
- 05 series — Supplement 1
- 05 series — Base text
- 04 series — Supplement 13
- 04 series — Supplement 12
- 04 series — Supplement 11
- 04 series — Supplement 10
- 04 series — Supplement 9
- 04 series — Supplement 8
- 04 series — Supplement 7