ISO 24478:2023

Overview

ISO 24478:2023 - Railway applications - Braking - General vocabulary is an international vocabulary standard that defines unambiguous terms used for brakes and braking in rolling stock. Rather than specifying performance limits or test methods, this document standardizes terminology for braking functions, components and behaviours (for example, braking, brake unit, parking, immobilizing, brake system compatibility). The standard was prepared by ISO/TC 269 (Railway applications, Subcommittee SC 2, Rolling stock) and includes informative annexes with charts and system overviews.

Key topics and technical coverage

ISO 24478:2023 organizes braking terminology into clearly defined topical groups, including:

• Basic definitions: core terms such as braking, brake, and brake unit.
• Brake system compatibility: definitions related to interoperability of coupled vehicles.
• Performance concepts: braking performance, deceleration, and related parameters.
• Purposes of braking: stopping, slowing, drag braking, holding, immobilizing and parking.
• Mechanics: braking force, retarding force, decelerating force, static/dynamic mass, wheel/rail adhesion and coefficient of adhesion.
• Kinematics and dynamics: delay time, build-up time, fully-established brake, free running distance, braking distance and stopping distance.
• Types and characteristics: classification of brake types (friction brakes, magnetic track brakes, etc.), application and release modes, and control strategies.
• Brake system components: command and control elements, sensors, control assemblies, energy storage and supply (air, hydraulic), friction components, and parking/hand brake equipment.
• Wheel slide protection (WSP), brake test types, symbols, abbreviations and informative annexes (A–E) covering timing, charts and system relationships.

Practical applications and benefits

• Provides a consistent vocabulary for technical specifications, design documentation, procurement, maintenance manuals and safety cases.
• Supports interoperability and brake system compatibility assessments for coupled rolling stock.
• Aids engineers and system integrators when specifying braking behaviour (e.g., delay/build-up times, braking distance definitions).
• Useful for regulators, certification bodies and test laboratories to ensure clear communication about braking requirements and test outcomes.
• Enables clear training materials and operator procedures by standardizing terms like holding, immobilizing and parking.

Who should use this standard

• Rolling stock designers and manufacturers
• Railway system integrators and signalling engineers
• Maintenance and testing organisations
• Regulators, conformity assessors and safety analysts
• Technical writers, trainers and procurement specialists

Related information

For cross-references and additional terminology, consult the ISO Online Browsing Platform and the IEC Electropedia. ISO 24478:2023 complements other ISO/TC 269 standards covering braking performance, tests and component specifications.