sonROAD18 is a Swiss road traffic noise emission model based on CNOSSOS-EU formalism, covering more than 10 vehicle categories with speed ranges 20–130 km/h, calibrated using over 700,000 pass-bys from 2015–2017. NExUS is a research model for noise from battery electric and internal combustion engine passenger cars during acceleration in urban scenarios, based on more than 3,000 real drive trajectories recorded in 2024, with speed ranges 0–60 km/h. Both models predict noise emissions via propulsion and rolling noise components using three octave bands.

This document requests sound model documentation through a series of questions. Two models are documented: sonROAD18, last updated October 2024, uses more than 10 vehicle classes and describes sound power levels using propulsion noise and rolling noise components with spectral model coefficients, vehicle speed, road gradient corrections, pavement corrections, and air temperature corrections. The reference pavement is ACMR8 with porosity less than 8%. NExUS, last updated 2025, uses two vehicle classes comparing battery electric vehicles and internal combustion engine passenger cars, describing sound power levels using spectral model coefficients, speed, and acceleration parameters. The reference pavement is dense asphalt concrete AC 11 S. Both models use omnidirectional directivity and position sources 0.05 m above road surface.

The 22nd session of the Task Force on Vehicles Sound will convene on Tuesday 1st September 2026 from 9:00 to 11:30 (CEST) as a hybrid meeting in Geneva. The agenda includes a cross-matrix comparison on approaches to sound traffic modelling, discussion on updating the guidelines of the Task Force as approved at GRBP-74 in September 2021, any other business, and confirmation of the next meeting provisionally scheduled for 20th October 2026 in Barcelona.

The Task Force Vehicles Sound Cross Matrix activity requests input on traffic sound models. Volunteer participants are invited to share information on noise mapping models used in their regions, including model name, year of last update, references, source descriptions, number of vehicle classes, vehicle class descriptions, formulas and parameters for each class, reference roads for tyre rolling sound, comparison to ISO 10844:2021 type approval test tracks, and propagation concepts used.