Since 2017, several porous asphalt trials have been built in New Zealand in order to investigate the effects of air voids, stone size and layer thickness on tyre/road noise. These trials have shown that all three variables play an important role in noise from porous asphalt surfaces. The trial results have led to a 40 mm thick EPA7 surface (porous asphalt with 7 mm nominal stone size) becoming the preferred low-noise surface for use on New Zealand State highways, with a slightly thicker 50 mm version being preferred in particularly noise-sensitive areas. Regular CPX testing is being conducted to monitor the long-term acoustic behaviour of the surfaces, and this testing has not shown any significant changes in LCPX:P1,80 to date. Further trials are planned for early 2022 to optimise the air voids content for the preferred EPA7 surface.