ISO 20138-1-2018 PDF

Full title and description

Railway applications — Calculation of braking performance (stopping, slowing and stationary braking) — Part 1: General algorithms utilizing mean value calculation. This International Standard defines general algorithms and formulae that use mean (average) input values to calculate braking performance for railway rolling stock (single vehicles or train formations), including stopping and slowing distances, stationary braking, braking power and energy, and examples for different brake equipment types.

Abstract

ISO 20138-1:2018 specifies methodologies for calculating braking performance of railway rolling stock using mean-value based algorithms. It provides the mathematical framework and worked examples to determine stopping distances, slowing distances and stationary braking behaviour for vehicles and train formations. The document is intended for use during design, testing, verification and investigation phases but does not set pass/fail acceptance criteria or prescribe brake-system selection. Methods to account for wheel-slip/wheel-slide activity (loss of adhesion beyond available adhesion) are not provided in this part.

General information

• Status: Published (current edition published October 19, 2018).
• Publication date: 19 October 2018.
• Publisher: International Organization for Standardization (ISO).
• ICS / categories: 45.020 (Railway engineering).
• Edition / version: Edition 1 (2018).
• Number of pages: 80.

Scope

This part of ISO 20138 specifies the general algorithms and computational procedures that use mean (average) input values to calculate braking performance for all types of rolling stock. It covers calculations for stopping distances, slowing distances, stationary braking, and related power and energy computations for single vehicles or train formations. It is applicable at design, manufacture, testing, verification and investigative stages, but it does not define performance acceptance criteria, nor does it provide procedures for assessing braking when adhesion is exceeded (wheel-slide/wheel-slip effects are outside this part).

Key topics and requirements

• Definition and formulation of mean-value based algorithms for braking calculations.
• Methods to compute stopping and slowing distances for vehicles and train formations.
• Calculation of stationary braking behaviour (holding/parking brake effects).
• Computation of braking power, energy and retarding forces using average inputs.
• Worked examples for different brake equipment types to illustrate the algorithms.
• Guidance on appropriate input data and assumptions; clarification that acceptance criteria and brake selection guidance are excluded.
• Limitations: no method for extension of stopping distances due to adhesion loss (wheel-slide activity) in this part.

Typical use and users

ISO 20138-1 is used by rolling stock designers, brake-system engineers, test laboratories, vehicle manufacturers, regulatory authorities, operators performing performance assessments, and investigators analyzing braking incidents. It is a technical reference for those who need standardized calculation procedures for braking performance during design verification, type testing, safety assessment and post-incident analysis.

Related standards

Relevant documents and related publications include other parts of the ISO 20138 series (notably ISO 20138-2 covering step-by-step / time-integration algorithms), ISO/TR country-specific guidance for applying the 20138 series, and more recent ISO documents on braking system general requirements (for example ISO 24221:2024). Users should consider the whole ISO 20138 series and applicable national/sector regulations when applying the methods in this part.

Keywords

braking performance, stopping distance, slowing distance, stationary braking, mean value calculation, railway rolling stock, brake algorithms, braking power, braking energy, retarding forces, ISO 20138

FAQ

Q: What is this standard?

A: ISO 20138-1:2018 is an International Standard that defines general, mean-value based algorithms for calculating braking performance (stopping, slowing and stationary braking) of railway vehicles and train formations.

Q: What does it cover?

A: It covers mathematical algorithms and worked examples using average input values to calculate stopping/slowing distances, stationary braking, braking power and energy. It is intended for assessment, testing and investigation stages but does not include acceptance criteria or design prescriptions.

Q: Who typically uses it?

A: Rolling stock designers, brake-system engineers, test houses, railway operators, safety assessors, regulators and investigators who need a standardised method for calculating braking performance.

Q: Is it current or superseded?

A: The published edition is Edition 1 (published 19 October 2018). As of 28 February 2026 this edition remains a published ISO standard; national bodies or ISO may publish amendments, corrigenda or revisions, so users should confirm the latest status with their national standards body or ISO before making compliance decisions.

Q: Is it part of a series?

A: Yes — ISO 20138 is a multi-part series. Part 1 provides mean-value algorithms; Part 2 provides step-by-step (time-integration) algorithms. There are also related technical reports and country-specific guidance documents associated with the series.

Q: What are the key keywords?

A: Braking performance, stopping distance, slowing distance, stationary braking, mean value calculation, railway rolling stock, brake algorithms, braking energy.