Originally the route began on the A601 in the centre of Luton. The start was later pushed back to a point on the A1081 bypass but now the route has returned to beginning closer to the town centre.
Today the B653 begins at a mini-roundabout on the A505 Windmill Road, from which it heads south past a retail park to reach a double roundabout (which is actually part of a simple GSJ with the A1081). Turn right at the first roundabout to get to the A1081; turn left at the second to reach Luton Airport Parkway station. The B653 goes straight on at both these roundabouts to pass under the A1081 and enter open country.
Lea Bridge Corner, East Hyde
The road now runs southeastwards, accompanying the Midland Main Line for a couple of miles before going under it, and following the course of the River Lea for much longer. It meets the B652 in Cold Harbour, on the edge of Harpenden, and is the dominant partner in a "multiplex" for about half a mile before that road resumes its independent existence by turning off to the right. The B653 continues ahead out of town and reaches Wheathampstead a couple of miles further on.
On the edge of Wheathampstead we meet the B651 at a roundabout. Originally there then followed another multiplex (i.e. the route ahead – running south along the High Street – was a section of the B651), the B653 resuming, and continuing eastward, at a left turn into Marford Road. Today, however, the B653 crosses the B651 at the aforementioned roundabout to run along a short bypass, crossing the River Lea en route, to pick up its old route at another roundabout. From here the B653 continues east, not as close to the river as before, through Lemsford to meet the B197 at a roundabout on the western edge of Welwyn Garden City – and immediately west of the A1(M), before passing beneath the latter to end at a roundabout junction with the A6129.
In the 1960s the entire length of the B653 was upgraded to Class I status, becoming the A6129. It was downgraded and reverted to its original number back at the same time as the A5 and A6 were removed from St Albans.