|From:||Ross on Wye (SO614259)|
|Length:||7.4 miles (11.9 km)|
|Meets:||A449, B4224, M50, B4222, B4215, B4216|
|Route outline (key)|
The first 6 km of the route – from the roundabout at the western terminus of the M50 (junction 4) to the notorious junction 3 ("the UK's only motorway T-junction") near Linton – parallels the motorway, though on a somewhat hillier course through Upton Bishop (where it intersects the B4224) to the north.
The motorway swings to the north-east here, but the B4221 continues eastward towards Kilcot on a 2.5-km-long near-straight stretch, crossing the county boundary at Gorsley and shortly afterwards being joined by the B4222 coming in from the right.
The final section of the route, from Kilcot to Newent, is less well aligned and subject to a 50 mph speed limit as well as a ban on overtaking throughout. The route ends at the north end of Newent High Street at a traffic-light-controlled junction from which the B4215 heads north and east and the B4216 goes south into the town centre.