Its route takes it in an arch (NW to SE) roughly west of the Royal Canal, which it crosses three times.

The main town en route is Ballymahon, where it crosses the N55 and the River Inny.

This largely accounts for the remarkable straightness of the R392 compared to other Regional roads in Ireland.

The route also closely passes the Hill of Uisneach, an even older royal and spiritual site than Tara located between the villages of Moyvore and Loughnavalley and place of origin of the festival of Bealtine.

West of Ballymahon, before crossing the River Shannon, the R392 runs adjacent and parallel to the Corlea Trackway, an ancient wooden trackway across a peat bog found by Bord na Mona workers in the 1980s and excavated fully in 1991.