Overview
ISO 21994:2022 - "Passenger cars - Stopping distance at straight-line braking with ABS - Open-loop test method" - defines a repeatable, reference test method to determine stopping distances for passenger cars and light trucks when the anti‑lock braking system (ABS) is fully engaged. The standard specifies test principle, required variables, measuring equipment, detailed test conditions and a data-evaluation framework to produce comparable, high‑repeatability results for emergency straight‑line braking on a high‑friction, dry surface.
Key topics and technical requirements
- Test principle: Open‑loop emergency (panic) braking with rapid brake pedal actuation in straight‑ahead driving to ensure ABS is active.
- Primary measured variables: longitudinal velocity, time of brake pedal actuation, longitudinal distance, and brake pedal actuation force.
- Key result metrics:
- stopping distance from initial pedal contact to standstill (A100),
- ABS‑braking distance from 90 km/h to standstill (L90),
- build‑up distance from pedal contact to a 10 km/h velocity reduction (F10).
- Measuring equipment: multi‑channel recording of appropriate transducers; recommended maximum errors (examples from the standard):
- initial and running velocity: ±0.5 km/h,
- longitudinal distance: ±1 % (≤50 m) or ±0.50 m (>50 m),
- pedal force: ±2 %; trigger at ≤10 N with ≤5 ms delay.
- Test conditions and preparation: specific requirements for track, environmental conditions (wind, temperature), tyre and brake conditioning, brake disc temperature monitoring, vehicle loading and general vehicle condition to ensure comparability.
- Data processing and repeatability: calibration, transducer installation rules (avoid pitch‑induced errors), procedures for multiple runs and normalization of stopping distances to enable robust comparisons.
Practical applications - who uses ISO 21994:2022
- Vehicle manufacturers and chassis engineers for ABS tuning, braking system validation and vehicle design.
- Independent test laboratories and OEM test tracks for performance benchmarking and certification‑grade measurements.
- Regulatory and type‑approval authorities requiring a standardized, repeatable method to compare stopping performance across vehicles.
- Tire and brake system suppliers evaluating component effects on emergency stopping and ABS interaction.
Related standards
- ISO 3833 - vehicle classification (scope applicability)
- ISO 8855 - vehicle dynamics vocabulary (terms and definitions)
- ISO 15037‑1:2019 - vehicle dynamics test methods; reference for reference system and general conditions
ISO 21994:2022 provides a standardized, high‑repeatability framework for accurate ABS stopping‑distance measurement - essential for safety assessment, development validation, and fair comparative testing.
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