The A5153 is a short link road, liberally scattered with roundabouts, on the southern edge of Holyhead. It came into being in 2001 following the construction of the A55 into town and has since been extended. However, the road lies entirely south of the A5 and is therefore out-of-zone.
The road starts at a roundabout on the A5 London Road in the middle of a retail park. It heads westwards and passes a couple of roundabouts providing access to various parts of the park. Soon a dumbbell roundabout is reached, which is junction 2 of the A55. On the far side, we enter open country and cross a roundabout giving access to an unclassified road before ending just afterwards at one final roundabout on the B4545. Some maps claim the A55 to B4545 section to be unclassified, although it is signed on the ground as A5153 throughout.
An amended OpenStreetMap trace for this route awaits uploading to the SABRE Wiki.