A blue sign with a diagram showing a branch off the road ahead and the following text.
Forward destinations: SOUTH WALES; Bristol; Swindon (W).
Exit destinations: Marlborough; A346; Swindon; A419.
Junction number: 15.
The signs at this junction always seem to undersell the A419. It's signposted for Swindon, which is just off this junction, but it's the start of a fast expressway that will take you to Gloucester and the M5 in no time.