ISO 12021:2010

Overview

ISO 12021:2010 - Road vehicles: Sensitivity to lateral wind - Open‑loop test method using wind generator input defines a repeatable laboratory-like procedure to quantify a vehicle’s dynamic response to lateral (cross) wind. The standard applies to passenger cars (ISO 3833), passenger car–trailer combinations and light trucks; applicability to motorcycles is still under investigation. The method uses wind generators to create a controlled lateral wind zone and records the vehicle’s open‑loop response (steering held fixed) to that input. ISO 12021 is intended to provide discriminatory, reproducible measures of lateral wind sensitivity - not to simulate every real driving condition.

Key technical topics and requirements

• Test principle: open‑loop exposure to a lateral wind input while the vehicle travels straight; steering-wheel held fixed for most of the run.
• Measured variables: mandatory - yaw velocity (ψ), lateral acceleration (ay), steering‑wheel angle (δ), longitudinal velocity (vx). Optional - lateral deviation, roll angle, sideslip, lateral velocity.
• Measuring equipment & accuracy: multi‑channel recording of time histories; recommended maximum errors (examples from standard) include yaw ±0.1°/s, lateral acceleration ±0.05 m/s², steering-wheel angle resolution <0.3°, longitudinal velocity ±0.4 m/s, lateral deviation ±0.02 m.
• Wind generator input: average lateral wind velocity 20 m/s ± 3 m/s (for ambient wind <1 m/s); nominal wind angle and velocity profiles over height and length must be documented. Wind zone length ≥ 15 m (preferably >25 m).
• Test track & environment: uniform hard surface, lateral gradient <2.5%, width and run‑off requirements, ambient wind ≤3 m/s during tests; dry surface recommended.
• Vehicle loading: tests at minimum (kerb mass + driver + instrumentation, ≤150 kg) and maximum (maximum authorized total mass per ISO 1176) loading conditions.
• Data handling: options to measure lateral deviation directly (instrumentation or dye‑trail) or compute it from on‑board signals; prescribed data analysis and result presentation (Annexes A & B).

Practical applications - who uses ISO 12021

• Vehicle manufacturers and design engineers assessing crosswind behavior during vehicle development.
• Automotive test labs and proving grounds executing crosswind / lateral wind sensitivity tests.
• Regulatory and safety research organizations comparing vehicle handling across models.
• Aerodynamicists and vehicle dynamics specialists developing stability control strategies. Note: ISO 12021 produces controlled, repeatable metrics useful for comparison, and any regulatory use requires demonstrated correlation with real‑world safety outcomes.

Related standards

• ISO 3833 - vehicle classification (passenger cars)
• ISO 8855 - vehicle dynamics vocabulary and definitions
• ISO 15037‑1:2006 - vehicle dynamics test methods - general conditions
• ISO 1176 - vehicle masses - codes and vocabulary

Keywords: ISO 12021, lateral wind sensitivity, open‑loop test, wind generator, crosswind test, vehicle dynamics, yaw velocity, lateral acceleration, passenger cars, light trucks.