|Length:||4.5 miles (7.2 km)|
|Meets:||unclassified, B4254, A472|
|Former Number(s):||B4254, A472|
|Old route now:||B4254|
|Route outline (key)|
The B4255 is a semi-rural B-road in eastern Glamorganshire.
It starts on an unclassfied road in Bedlinog, at the junction of the High Street with Moriah Street. It runs east then south along the High Street, descending steeply as it does so.
After a couple of hairpin bends the road reaches the bottom of the Bargoed Valley and levels out. It enters open country for a distance before reaching Trelewis where it becomes sprinkled with speed humps. Here it meets the B4254 and is the dominant partner in the multiplex south along the High Street.
Originally the northern end of the B4255 was on the A470 (now A4054) in Edwardsville. It headed east to Trelewis before following its current route to Nelson. The road from Trelewis to Bedlinog was originally unclassified but numbered as an extension of the B4254 early on, then in 1935 the two roads swapped numbers north of Trelewis, so that the B4254 went to Edwardsville and the B4255 to Bedlinog, as they do today.