IWG RD-ASEP is developing a mandatory procedure for UN R51 after the monitoring phase, with R41 work concluded. The Data Analysis Task Force reported in October 2025 on vehicle database sufficiency, boundary conditions, and CVT vehicle modeling. An Editing Task Force created a consolidated R51.04 draft reviewed in December 2025. IWG RD-ASEP recommends that no monitoring requirements be approved without corresponding mechanisms to collect, analyze, and report results. Submission targets shifted to September 2026 for informal document and February 2027 for working document due to database finalization and financial support needs.

The RD-ASEP informal group met in February 2026 in Geneva. The Analysis Task Force requested additional data on hybrids, CVT transmissions, and battery electric vehicles. The Editing Task Force addressed copyright issues with UN and ISO Secretariats, determining that current document practices continue unchanged. The group clarified that RD-ASEP development focuses on measurement procedures for real driving conditions and noise emission limits under full and partial load, not establishing a new regulatory phase.