The A4259 is an urban A-road in the Wiltshire town of Swindon. It follows the former A345 into town along that road's upgraded route as part of the construction of the New Town. The road presumably gained the A4259 number when the A345 was truncated south of the M4.
The road starts at a GSJ on the A419 just north of M4J15 and heads northwestwards into town. The road is a wide D2, rural to begin with. However, there are a few side turnings and gaps in the central reservation to facilitate these. Presently a roundabout is reached on the B4006 "ring road", which is where the pre-New Town route of the A345 turns off to the left.
Continuing ahead, the road remains D2, although the quality seems to lessen. There are now houses fronting onto the road and residential areas off to both sides. We bend right then left and, now with a northbound bus lane, soon reach our terminus roundabout on the A4312 in the Walcot area of town.
Until at least the 2000s the A4259 continued on from here. It bore left along the A4312 to the Magic Roundabout before following the isolated section of the A4289 under the railway line to end on the A4311. There is no obvious reason why the change was needed.