ETRTO proposed three ways to estimate service life (TA-36-04): tread depth measurements, initial tread depth and abrasion index, and tread mass. JRC presented a service life index (TA-32-04) based on tread depth measurements and conducted a preliminary assessment of the second concept. Service life is estimated by linear extrapolation to 1.6 mm from tread measurements at test start and end. The Service life index is calculated as the ratio of candidate to reference tyre service life. Next steps include confirming the equation for service life via tyre characteristics and clarifying which tyre characteristics are needed.

The document presents reflections on equivalence criteria for C2 tyres under Annex 4. C1 and C2 protocols are expected to remain very similar, with most changes having no impact on ALI and facility correlation. Key differences include tyre load and inflation pressure specifications. The main hypothesis states that if final C2 methods remain closely aligned to C1 methods, the existing equivalence framework for C1 could be maintained and extended to C2 testing, with already equivalent facilities receiving automatic equivalence or minor validation, and new facilities requiring amendment of Annex 4 to accept a mix of C1 and C2 tyres for demonstration of equivalence.