The present B573, like the original, runs in the area of the Northamptonshire town of Wellingborough. The road was originally unclassified but seems to have gained its number after World War II.
The road starts at traffic lights on the A4500 (former A45) which runs to the north of Earls Barton. We head south to skirt the western edge of the village and then descend to a roundabout which gives access to/from the eastbound A45. An unclassified road continues on to serve the westbound slip roads. All this makes up A45 J10.
The above was a spur, however; the mainline of the B573 turned left at a TOTSO to run through the centre of Earls Barton. After zigzagging around the church (famous for its Anglo-Saxon tower) the road passes the village green and then continues along Broad Street. It takes some time to reenter open country and by the time we have, we cross the A45 at J11 very soon afterwards. The next village is Great Doddington, where we run along the High Street, after which we go over the A45 once more. There is a westbound onslip here but no other movements between the two roads.
On the far side of the A45 we TOTSO right and run alongside the A-road for a short distance as far as the northern roundabout of the dumbbell J14. There's then a multiplex along the A509 to the next roundabout where that road turns right and we continue ahead. After cannoning off the River Nene we head north along the Embankment and pass through an industrial estate before crossing the B571 at a mini-roundabout. A stream is then crossed and we soon reach the B572, which we cross at a staggered crossroads.
The road continues north through the eastern suburbs of Wellingborough and it isn't long before the end of the road, at a roundabout on the A5128.