ISO 20138-1:2018

Overview - ISO 20138-1:2018 (Railway braking performance)

ISO 20138-1:2018 establishes general algorithms for calculation of braking performance of railway rolling stock using mean-value inputs. It covers methods to compute stopping distance, slowing distance, stationary braking, and associated power and energy metrics for single vehicles and train formations. The standard is intended for global use and supports assessment activities across design, manufacture, testing, verification and investigation stages. It defines calculation approaches but does not set pass/fail acceptance criteria, prescribe brake system selection, or model wheel-slide extensions when adhesion is exceeded.

Key technical topics and requirements

• Mean-value calculation algorithms for brake performance (Part 1 approach).
• Vehicle characteristics: static, dynamic and equivalent rotating mass, wheel diameter and related parameters.
• Brake equipment characteristics:
  • Adhesion-dependent types (e.g., tread, disc, electro-dynamic, retarders, eddy current).
  • Adhesion-independent types (e.g., magnetic track brake, linear eddy current).
• Time characteristics and equivalent response time for brake application.
• Forces and effects on gradients, blending of multiple brake types, and mean adhesion requirements.
• Calculations for stopping/slowing distances on level and graded track, including equivalent deceleration and free-running distance.
• Supplementary dynamic outputs: braking energy and maximum braking power per brake type.
• Stationary braking: holding, immobilization and parking brake calculations, static friction coefficients, safety ratios and maximum achievable gradients.
• Informative annexes with workflows, worked examples and calculation methodologies to aid implementation.

Practical applications - who uses ISO 20138-1

• Railway vehicle designers and manufacturers for consistent brake-performance assessments.
• Test engineers and verification bodies performing braking performance calculations during commissioning and certification.
• Operators and infrastructure managers validating stopping distances and parking/holding safety for service operations.
• Accident investigators and safety analysts reconstructing braking scenarios using standardised algorithms.
• Regulators and technical committees seeking harmonised methods to compare or reference braking calculations internationally.

Related standards

• ISO 20138-2 (complements Part 1): provides step‑by‑step methodology using instantaneous brake force values.
• Produced by ISO/TC 269 (Railway applications); intended to be used alongside national/regional safety and vehicle-acceptance rules.

Keywords: ISO 20138-1, braking performance, railway, stopping distance, slowing distance, stationary braking, brake calculation, rolling stock.