A4252 being reduced to D1
The A4252 is an entirely dual carriageway link between the A41 and M5 at J1 near West Bromwich and the A457 at Smethwick, in the Black Country. The A4182 is met at a roundabout about halfway along. Whilst the A4252 is a short but locally important link, its confusing numbering history make it more interesting than average.
The road was shown in early editions of the relevant OS Landranger sheet as being a B-class road, but no number is listed alongside the road (it was possibly the B4168 whose route was parallel); whilst from about 1979 it was upgraded to A-class and became an extension of the A4031 via a multiplex with the A41. This numbering was replaced in 1981 when the A4031 was diverted via Oldbury Town Centre near its original route, and from between then and 2004 it held the number A4168, which is deeply confusing as the "real" A4168 is in Dudley, approximately 5 miles away. Confusingly, whilst the signage at M5 J1 shows the correct number, as at December 2017, the road markings on the roundabout and approaches still state A4168, over 13 years after the route lost that number.