ISO 24221:2024/Amd 1:2026

• Status: Published
• Publication Date: 21-Sep-2026
• ICS: 45.060.01 - Railway rolling stock in general
• Technical Committee: ISO/TC 269/SC 2 - Rolling stock
• Drafting Committee: ISO/TC 269/SC 2/WG 1 - Railway braking
• Current Stage: 6060 - International Standard published
• Start Date: 22-Sep-2026
• Due Date: 03-Sep-2026
• Completion Date: 22-Sep-2026

• Amends: ISO 24221:2024 - Railway applications — Brake system — General requirements
• Effective Date: 07-Sep-2024

ISO 24221:2024/Amd 1:2026 is an ISO amendment to Railway applications - Brake system - General requirements. It updates the brake-system wording and several technical requirements for emergency braking, brake blending, load and payload conditions, and brake-performance testing for rail vehicles, units and trains. Engineers, assessors, and buyers use it to apply the revised requirements to the first edition of ISO 24221.

What does ISO 24221:2024/Amd 1:2026 specify?

ISO 24221:2024/Amd 1:2026 specifies targeted changes to the first edition of ISO 24221:2024. The amendment is organized as edits to the title and to subclauses 3.9, 4.2, 4.4, 5.2.1, 5.3, 5.5.2 and 5.5.5.

Location	What it covers
Title	Corrects the wording from “Braking system” to “Brake system”
3.9	Deletes one terminological entry
4.2	Adds safety-analysis requirements linked to emergency braking
4.4	Revises brake blending behavior and its relationship to adhesion demand
5.2.1	Updates a speed term to “maximum design speed”
5.3	Replaces the load and payload conditions used for brake design
5.5.2	Revises emergency-braking and duty-cycle test conditions
5.5.5	Updates a speed reference in the duty-cycle text

What are the key requirements of ISO 24221:2024/Amd 1:2026?

ISO 24221:2024/Amd 1:2026 tightens how emergency braking, brake blending, payload conditions, and tests are handled. The practical effect is that users must align the brake design and verification work with the amended wording before claiming conformance to the base standard.

Emergency braking needs safety analysis in more cases

ISO 24221:2024/Amd 1:2026 adds that if a dynamic brake subsystem is involved in emergency braking, it shall be subject to a safety analysis. The same applies when brake management or brake blending is used in emergency braking. In practice, this means the engineer must document the hazard review for the emergency-brake function, not just the hardware layout.

Brake blending is defined more explicitly

ISO 24221:2024/Amd 1:2026 says brake blending can happen at local level, train level, or both. It can use more than one brake system at the same time, or substitute the braking force of one unit or subsystem with another. The amendment also says service brake demand should start the dynamic brake units or subsystems first, if they can meet the required performance, and that blending shall respect the maximum adhesion demand set out in 5.6. In practice, that affects control logic and how braking effort is shared across systems.

Load and payload conditions are tied to braking performance

ISO 24221:2024/Amd 1:2026 replaces subclause 5.3 so the brake system must meet braking performance over the full range of expected operating load conditions. It uses design mass in working order (MVD) and design mass under normal payload (MND) as the basic load conditions, and introduces design mass under maximum braking payload (MXB) as MVD plus the maximum braking payload. For users, this means the brake design and calculations must cover the intended passenger and cargo loading cases, not only an empty or nominal vehicle.

Test conditions are updated to match the new load basis

ISO 24221:2024/Amd 1:2026 revises 5.5.2 so the emergency-brake tests include two consecutive emergency brake applications from maximum design speed at MXB on level track with a fully functional brake installation, plus the most challenging duty cycle at MXB in normal and degraded mode. This means the test plan has to show performance under repeated and degraded conditions, not only a single nominal run.

What terms does ISO 24221:2024/Amd 1:2026 define?

• Brake blending - The use of more than one brake unit or subsystem to provide the required braking force, either together or by substitution.
• Dynamic brake subsystem - The dynamic braking part of the system that, when used in emergency braking, triggers the need for safety analysis.
• Service brake demand - The request for a service brake application, such as from the driver or a train-protection system.
• Design mass in working order (MVD) - The base design mass used for braking-purpose calculations.
• Design mass under normal payload (MND) - The design mass used when the vehicle is loaded at normal payload conditions.
• Design mass under maximum braking payload (MXB) - The design mass used for maximum braking cases, calculated from MVD and the maximum braking payload.

Who uses ISO 24221:2024/Amd 1:2026?

ISO 24221:2024/Amd 1:2026 is used by rolling stock designers, brake system engineers, safety analysts, test laboratories, and technical purchasers. It is relevant for railway manufacturers, integrators, fleet owners, and certification teams that need to specify, assess, or verify brake performance on rail vehicles, units, or trains.

What changed in ISO 24221:2024/Amd 1:2026 from the previous edition?

ISO 24221:2024/Amd 1:2026 amends ISO 24221:2024. The stated changes are the title correction, deletion of one terminological entry in 3.9, new safety-analysis text in 4.2, a rewritten brake-blending subclause in 4.4, wording updates in 5.2.1, a full replacement of 5.3 on load and payload conditions, and revised test wording in 5.5.2 and 5.5.5.

Which standards are used with ISO 24221:2024/Amd 1:2026?

• ISO 24478 - Defines the applicable brake blending modes referenced in 4.4.
• ISO 10516 - Defines MVD and MND, which are used in the braking load and payload calculations in 5.3.
• EN 14198:2016+A2:2021 - Cited in a footnote for the European basis of standing-area payload assumptions for high-speed and long-distance trains.
• EN 16185-1:2014+A1:2020 - Cited in a footnote for the European basis of standing-area payload assumptions for other train types.

What does the ISO 24221:2024/Amd 1:2026 document contain?

This amendment contains replacement text for selected clauses rather than a full rewrite of the base standard. Its most substantial technical content is the new 5.3 text and Table 3 on maximum braking payload, which organizes payload assumptions by area and vehicle use case. The document also revises the emergency-braking test setup in 5.5.2 and a speed reference in 5.5.5, so it is useful when updating design calculations, test procedures, and conformity checks.

International
Standard
ISO 24221
First edition
Railway applications — Brake
2024-03
system — General requirements
AMENDMENT 1
AMENDMENT 1
2026-09
Applications ferroviaires — Système de freinage — Exigences
générales
AMENDEMENT 1
Reference number
ISO 24221:2024/Amd.1:2026(en) © ISO 2026

ISO 24221:2024/Amd.1:2026(en)
© ISO 2026
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting on
the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address below
or ISO’s member body in the country of the requester.
ISO copyright office
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: [phone]
Email: [e-mail]
Website: www.iso.org
Published in Switzerland
ii
ISO 24221:2024/Amd.1:2026(en)
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards
bodies (ISO member bodies). The work of preparing International Standards is normally carried out through
ISO technical committees. Each member body interested in a subject for which a technical committee
has been established has the right to be represented on that committee. International organizations,
governmental and non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely
with the International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.
The procedures used to develop this document and those intended for its further maintenance are described
in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the different types
of ISO documents should be noted. This document was drafted in accordance with the editorial rules of the
ISO/IEC Directives, Part 2 (see www.iso.org/directives).
ISO draws attention to the possibility that the implementation of this document may involve the use of (a)
patent(s). ISO takes no position concerning the evidence, validity or applicability of any claimed patent
rights in respect thereof. As of the date of publication of this document, ISO had not received notice of (a)
patent(s) which may be required to implement this document. However, implementers are cautioned that
this may not represent the latest information, which may be obtained from the patent database available at
www.iso.org/patents. ISO shall not be held responsible for identifying any or all such patent rights.
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and expressions
related to conformity assessment, as well as information about ISO's adherence to the World Trade
Organization (WTO) principles in the Technical Barriers to Trade (TBT), see www.iso.org/iso/foreword.html.
This document was prepared by Technical Committee ISO/TC 269, Railway applications, Subcommittee SC 2,
Rolling stock.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www.iso.org/members.html.

iii
ISO 24221:2024/Amd.1:2026(en)
Railway applications — Brake system — General
requirements
AMENDMENT 1
Title
In the title, replace “Braking system” with “Brake system”.

3.9
Delete the entire terminological entry.

4.2, fifth paragraph
At the end of the first sentence, replace “up to the maximum braking load.” with “up to the design mass
under maximum braking payload.”

4.2, eight paragraph
At the end of 4.2, add the following two paragraphs:
If a dynamic brake subsystem is involved in emergency braking it shall be subject to a safety analysis.
If brake management or brake blending is used in emergency braking it shall be subject to a safety analysis.

4.4
Replace the text wit
...

Norme
internationale
ISO 24221
Première édition
Applications ferroviaires — Système
2024-03
de freinage — Exigences générales
AMENDEMENT 1
AMENDEMENT 1
2026-09
Railway applications — Brake system — General requirements
AMENDMENT 1
Numéro de référence
ISO 24221:2024/Amd.1:2026(fr) © ISO 2026

ISO 24221:2024/Amd.1:2026(fr)
DOCUMENT PROTÉGÉ PAR COPYRIGHT
© ISO 2026
Tous droits réservés. Sauf prescription différente ou nécessité dans le contexte de sa mise en œuvre, aucune partie de cette
publication ne peut être reproduite ni utilisée sous quelque forme que ce soit et par aucun procédé, électronique ou mécanique,
y compris la photocopie, ou la diffusion sur l’internet ou sur un intranet, sans autorisation écrite préalable. Une autorisation peut
être demandée à l’ISO à l’adresse ci-après ou au comité membre de l’ISO dans le pays du demandeur.
ISO copyright office
Case postale 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Genève
Tél.: [phone]
E-mail: [e-mail]
Web: www.iso.org
Publié en Suisse
ii
ISO 24221:2024/Amd.1:2026(fr)
Avant-propos
L’ISO (Organisation internationale de normalisation) est une fédération mondiale d’organismes nationaux
de normalisation (comités membres de l’ISO). L’élaboration des Normes internationales est en général
confiée aux comités techniques de l’ISO. Chaque comité membre intéressé par une étude a le droit de faire
partie du comité technique créé à cet effet. Les organisations internationales, gouvernementales et non
gouvernementales, en liaison avec l’ISO participent également aux travaux. L’ISO collabore étroitement avec
la Commission électrotechnique internationale (IEC) en ce qui concerne la normalisation électrotechnique.
Les procédures utilisées pour élaborer le présent document et celles destinées à sa mise à jour sont
décrites dans les Directives ISO/IEC, Partie 1. Il convient en particulier de prendre note des différents
critères d’approbation requis pour les différents types de documents ISO. Le présent document
a été rédigé conformément aux règles de rédaction données dans les Directives ISO/IEC, Partie 2
(voir www.iso.org/directives).
L’ISO attire l’attention sur le fait que la mise en application du présent document peut entraîner l’utilisation
d’un ou de plusieurs brevets. L’ISO ne prend pas position quant à la preuve, à la validité et à l’applicabilité de
tout droit de brevet revendiqué à cet égard. À la date de publication du présent document, l’ISO n’avait pas
reçu notification qu’un ou plusieurs brevets pouvaient être nécessaires à sa mise en application. Toutefois,
il y a lieu d’avertir les responsables de la mise en application du présent document que des informations
plus récentes sont susceptibles de figurer dans la base de données de brevets, disponible à l’adresse
www.iso.org/patents. L’ISO ne saurait être tenue pour responsable de ne pas avoir identifié de tels droits de
brevets et de ne pas avoir signalé leur existence.
Les appellations commerciales éventuellement mentionnées dans le présent document sont données pour
information, par souci de commodité, à l’intention des utilisateurs et ne sauraient constituer un engagement.
Pour une explication de la nature volontaire des normes, de la signification des termes et expressions
spécifiques de l’ISO liés à l’évaluation de la conformité, ou pour toute information au sujet de l’adhésion de
l’ISO aux principes de l’Organisation mondiale du commerce (OMC) concernant les obstacles techniques au
commerce (OTC), voir le lien suivant: www.iso.org/iso/foreword.html.
Le comité chargé de l’élaboration du présent document est l’ISO/TC 269, Applications ferroviaires, Sous-
comité SC 2, Matériel roulant.
Il convient que l’utilisateur adresse tout retour d’information ou toute question concernant le présent
document à l’organisme national de normalisation de son pays. Une liste exhaustive desdits organismes se
trouve à l’adresse www.iso.org/members.html.

iii
ISO 24221:2024/Amd.1:2026(fr)
Applications ferroviaires — Système de freinage — Exigences
générales
AMENDEMENT 1
Titre
Dans le titre, replacer «Braking system» par «Brake system» (valable uniquement pour la version anglaise).

3.9
Supprimer l’entrée terminologique entière.

ème
4.2, 5 alinéa
À la fin de la première phrase, remplacer «jusqu’à la charge maximale de freinage.» par «jusqu’à la masse de
conception en charge maximale de freinage.»

ème
4.2, 8 alinéa
À la fin de 4.2, ajouter les deux alinéas suivants:
Si un sous-système de freinage dynamique est impliqué dans le freinage d’urgence, il doit être soumis à une
analyse de sécurité.
Si la gestion du freinage ou la conjugaison des freins est utilisée lors d’un freinage d’urgence, elle doit être
soumise à une analyse de sécurité.

4.4
Remplacer le texte par ce qui suit:
La conjugaison des freins peut se faire soit au niveau loca
...