Mynachdy Interchange was a planned junction in Cardiff where the unbuilt Llantrisant Radial would have joined the A48.
Two routes were planned for the Llantrisant Radial
. They were the Buchanan and River routes. The location of the junction would be dependant on which route was selected. The road was never built and the only clue that the junction was planned is the splaying of the Western Avenue slip roads at Gabalfa Interchange
which were built to allow provision for the junction that was never needed in the end.