Version 3: Updates on further activity (Sect. 6.2) This document is the outcome of activities within Task 6.4, which has explored new trans-national access (TNA) modalities for public authorities (Leader: NOA, participants: UCC, INOE, CNRS, FZJ). Public authorities (PA) responsible for measuring, reporting and acting on air pollution (local government, civil protection and environmental/ health agencies) need atmospheric measurements. Atmospheric Research Infrastructures (RIs) have excellent potential to support the efforts of public authorities in this area. The purpose of this task has been to identify the specific needs of public authorities, develop tailored modalities for access to multiple components from the atmospheric RΙs and propose a TNA pilot involving the ATMO-ACCESS European atmospheric research facilities and public authorities from Europe. The proposed TNA activity involves flexible access modalities and tailored services in support of informed decision making by public authorities.