The Cross Matrix activity began with TFSL-02-07 (May 2021) defining the concept to assess regulation effects across different areas. TFVS-04-14 (Sep. 2021) clarified building a sound model. Early work 2021-2022 defined traffic and fleet scenarios through TFVS-05-06, TFVS-06-03, TFVS-07-08, and TFVS-06-05, which selected eight scenarios from residential areas to motorways. Activity decreased by 2023, with TFVS-12-06 calling for resumption. TFVS-17-07 compared model results from EU, Switzerland, Japan, and HMG Akustiklabor. Future steps include addressing L_max, traffic measure effects, opening the approach to L categories, and assessing progress from new RD-ASEP in UN R41 06 series.

This presentation reviews the consideration of cross matrix modules to enable GRBP and subgroups to evaluate regulation amendment proposals regarding their impact on real world traffic. The cross matrix addresses how vehicle sound emission regulations influence sound levels considered by road traffic noise models. Four existing sound source models are compared: EU CNOSSOS, SonRoad18, CNOSSOS JP, and HMG ASJ RTN. HMG sound power models derived from pass-by data on ISO 10844 compliant test tracks evaluate EVs and include type approval data for ASEP and RD-ASEP. Statistical pass-by simulations using randomized vehicle selection enable calculation of LA, eq for traffic scenarios with varying fleet compositions. To advance this work, sound power models for missing UN R51.03 and UN R41 vehicle categories, especially buses and trucks and new propulsion technologies, must be created and reference scenarios established and agreed upon.

The 20th session of the Task Force on Vehicle Sound convened on 14 April 2026. The session adopted the draft agenda and reviewed the 19th session report with a minor correction. The cross-matrix, defined in 2021 to assess traffic noise reduction policies through traffic scenarios and models, was rediscussed. A model based on RD-ASEP monitoring data was presented, showing significant deviations from EU-CNOSSOS predictions. Additional data are needed for M₃/N₃ and L-category vehicles. Extension of the cross-matrix to L-categories was proposed, utilising data from UN R41-06 RD-ASEP. A subgroup was established to develop scenarios, particularly for L-categories, and review available models. The next meeting is scheduled for 9 June 2026.