|Location Map ( geo)|
|Modified 3-level stacked roundabout|
|Llantrisant Radial, Western Tangential|
|Junctions related to the A48(M) (Llantrisant Radial)|
Radyr Interchange was a planned junction that ultimately would connect the Llantrisant Radial to the Western Tangential. The Llantrisant Radial would be built many years in advance of the Western Tangential so the junction would initially be a Diamond interchange serving the A4119. However things are complicated due to there being two alternative routes for the Llantrisant Radial. These were known as the Buchanan Route and the River Route. The Buchanan Route would have ran to the north and the diamond interchange there would close when the Western Tangential opened. The River Route would have ran further south and the bridge carrying the diamond interchange would have formed the western side of a new roundabout interchange. The River Route was eventually chosen shortly before the entire plan was scrapped.
The Buchanan Route was the first proposed route for the Llantrisant Radial and the earliest plans show a trumpet interchange immediately to the east of the main junction. This was for a shopping centre. There would clearly have been weaving issues between the two closely spaced junctions which may explain why later plans omit this junction.
This later plan shows the position and junction layouts for the two Llantrisant Radial routes. At the time no decision had been taken as to which route would eventually be chosen. The roads in black would be built first and the junction for either route was to be a diamond. The junction would become a modified 3-level stacked roundabout when the Western Tangential was added and this is shown in grey on the map. The diamond interchange would close and become a simple bridge for the Buchanan Route. The River Route would see it become the western side of the new roundabout but it's not clear from the plans whether there would be east facing slips onto the Llantrisant Radial. The nearby junction at Radyr Court Road would cause weaving without modification.
Despite first appearances from the map, there would never have been two Llantrisant Radials running parallel - it was either one or the other. For the Buchanan Route there would have been two junctions on the Western Tangential at the locations shown with the southern junction being a diamond where it crosses the A4119.
|M4 (E), City centre|
|Merthyr Tydfil (A470)|