ISO 8608:2016

Overview

ISO 8608:2016 - Mechanical vibration - Road surface profiles - Reporting of measured data defines a uniform method for reporting measured vertical road profile data. The standard covers both one-track and multiple-track measurements on roads, streets, highways and off‑road terrain (rail‑track data are excluded). ISO 8608:2016 specifies what to report (data formats, plots and metadata) but does not prescribe measurement hardware or processing methods - though key characteristics of the measuring system must be documented.

Key topics and technical requirements

• Preferred descriptors: The recommended primary descriptor is the displacement power spectral density (displacement PSD) of the vertical road profile. Reporting of non‑smoothed PSD is always required; acceleration PSD is an allowed alternative.
• PSD relationship: The standard specifies the mathematical relationship between displacement PSD and acceleration PSD (conversion is a function of spatial frequency).
• Spatial frequency range: Users report PSD over a spatial frequency range suitable to the vehicle, road or product; common practical limits are noted (e.g., lower limits typically not below 0.01 cycles/m for on‑road data).
• Smoothing requirements: To reduce statistical fluctuations the PSD shall be presented in a smoothed form using:
  • octave bands up to 0.0312 cycles/m,
  • one‑third‑octave bands up to 0.25 cycles/m,
  • one‑twelfth‑octave bands above that up to the highest calculated frequency.
• Decolouring: Raw PSDs must be decoloured (corrected) for the measuring system transfer function where applicable.
• Reporting content: Standardizes curve sheets and report content for one‑track and multiple‑track data, parameters of analysis, and test conditions. Annexes provide examples, characterization/fitting guidance, statistical use guidance and FFT/precision considerations.
• Normative references: Includes references such as IEC 61260‑1 and uses terms from ISO 2041.

Practical applications and users

ISO 8608:2016 is used by:

• Vehicle and suspension designers (NVH, ride comfort simulation)
• Tire and wheel manufacturers assessing road inputs
• Pavement engineers and road authorities compiling surface condition data
• Researchers modelling vehicle–road interaction and conducting simulation studies
• Environmental/noise specialists who need standardized road surface inputs

The standard enables consistent exchange of road profile PSD data for simulation, product development, monitoring and comparative studies.

Related standards

• IEC 61260‑1 (octave‑band and fractional‑octave‑band filters) - referenced for band definitions
• ISO 2041 - terminology for vibration measurement

Keywords: ISO 8608:2016, road surface profiles, mechanical vibration, power spectral density (PSD), road profile measurement, displacement PSD, acceleration PSD, smoothing, spatial frequency.