The A1302 follows some of the former route of the A45 through Bury St Edmunds, before the construction of the line now used by the A14.
The road starts at A14J42 just to the north of Westley, where is also meets the cross-shaped B1106. The road heads east and crosses the Newmarket to Bury St Edmunds railway line immediately. After running parallel to the A14 to begin with, the two roads separate as we enter town and the other road turns away to bypass it.
We continue east through the suburbs and pass a castellated prison-like building, Gibraltar Barracks, the HQ of the Royal Anglian Regiment. The West Suffolk College is then passed and the road reaches a roundabout on the town centre western relief road. The old A45 continued ahead. We have a spur to the left which takes us via a few mini-roundabouts to a full roundabout to the north of the town centre where we meet the A1101 and A143.
The mainline of the A1302 turns right onto a D2 road through an out-of-town retail park. We then reach a double mini-roundabout where the A143 (which has been the junior partner in a multiplex) regains its number and heads west, whilst we narrow and cross the River Linnet. The road continues through the marshes to the south of the town centre and looks rural for a short distance. We reenter the urban area (although no buildings are accessible from the A1302) and turn left at a roundabout to end at the next roundabout on the A134. This is the spot where we rejoin the ex-A45, which continues ahead back to the A14.