Overview
ISO 10521-1:2006 - "Road vehicles - Road load - Part 1: Determination under reference atmospheric conditions" defines internationally accepted methods to determine a vehicle’s road load for laboratory and regulatory test purposes (for example, fuel consumption and exhaust emission measurements). The standard covers on-road and off-road measurement techniques - coastdown, torquemeter, and wind-tunnel/chassis-dynamometer methods - and specifies how to correct results to defined reference atmospheric conditions. It applies to motor vehicles (ISO 3833) up to a gross vehicle mass of 3 500 kg.
Key topics and requirements
- Measurement methods
- Coastdown method (multi-segment, average deceleration, direct regression)
- Torquemeter method (in-drive-train running-resistance measurement)
- Wind-tunnel + chassis-dynamometer method (separate aerodynamic drag and rolling resistance)
- Reference atmospheric conditions
- Pressure, temperature and dry air density values to which results are corrected; wind speed = 0 m/s
- Wind and anemometry
- On-road tests permitted with average wind speeds up to 10 m/s (gusts ≤ 14 m/s) with required wind correction
- Stationary or onboard anemometry specified depending on average and cross-wind components
- Test-environment and road surface
- Flat, dry, hard road surface representative of urban/highway textures; longitudinal slope ≤ ±1 %, local deviations constrained
- Atmospheric temperature allowed: 274 K to 308 K
- Vehicle preparation
- Normal service condition (tyre pressures, wheel alignment, lubricants), closed windows/hood, A/C off, specified vehicle mass including driver and instruments
- Tyre soaking/pressure adjustment procedures to ensure repeatability
- Required measurement accuracy
- Vehicle speed ±0.5 km/h or ±1 %; time ±50 ms or ±0.1 %; wheel torque ±3 N·m or ±0.5 %; wind speed ±0.3 m/s; SCd ±2 %; etc.
Practical applications and users
- Regulatory bodies and test labs performing fuel consumption, CO2 and exhaust emissions testing
- Automotive OEMs for vehicle development, aerodynamic tuning and rolling-resistance optimization
- Independent test houses and certification bodies that reproduce road load on chassis dynamometers
- Wind-tunnel facilities and metrology labs seeking to align measurements with international reference conditions
Related standards
- ISO 10521-2: Reproduction of road load on chassis dynamometer
- ISO 3833: Road vehicles - Types - Terms and definitions
- ISO/IEC 17025: Testing and calibration laboratory competence (recommended for wind-tunnel measurement quality)
ISO 10521-1 provides a robust framework for reliable, repeatable road-load determination - essential for accurate laboratory simulation, regulatory compliance and vehicle performance benchmarking. Keywords: ISO 10521-1, road load, coastdown method, torquemeter, wind tunnel, chassis dynamometer, reference atmospheric conditions.