This study aims to examine the impact of increased levels of CNG fast refill stations on the operation of the transmission and distribution gas networks in both the Republic of Ireland (RoI) and Northern Ireland (NI). To that end, a cross border pilot network of 17 CNG units (the global project foresees 134) along the TEN-T Core Road Network, to a large extent on the CNC North Sea – Mediterranean between the RoI and NI will be built as a pilot activity to assess the impact on the gas network. Activities will encompass developing understanding of the operation and planning of the network, CNG equipment and user demand patterns and behaviours, and the injection of renewable gas into the gas transmission system.