The A5121 is the former route of the A38 through Burton upon Trent, Staffordshire, before it was moved onto the Burton Bypass.
On completion of the bypass in 1966 the newly designated A5121 ran from the new grade-separated junction in Branston, along Burton Road (Branston) and Branston Road (Burton) into Burton town centre before being met by the B5017 (from Uttoxeter) at the Abbey Arcade. From here it travelled along the length of the High Street to reach the Queens Hotel, a short distance from the Trent river bridge.
The road then turned left (west) on to the A50, now the A511, for quarter of a mile before crossing the mainline railway and coming to Derby Turn. Here the road turned right (north) along Derby Road to reach the new grade-separated junction with the A38 at Clay Mills.
The mid-1990s saw significant road improvements in Burton, with the route of the A5121 through the town changing markedly. The 'old' road was downgraded to the B5018 from near the A38 GSJ at Branston along most of its length to the roundabout next to the new Burton Albion Football Club's Pirelli Stadium. The A5121 now takes a new route from the Branston GSJ directly to a crossroads junction with the B5017 at Shobnall Road and the A5189, which heads east to cross St. Peter's Bridge over the Trent to meet the A444 on the east bank. From here it continues past the Town Hall, negotiates a one-way system by the railway station, and onward to meet the A511 at Derby Turn. This new route is almost an exact shadow of the Roman road (Ryknild Street) from Wall, near Lichfield, to Little Chester in Derby.
Road improvements in 2008/9 have seen the A5121/A5189 roundabout replaced by traffic lights, and a dual-carriageway section created from the A38 GSJ along the A5121 for 700 metres.
The western and southern areas of the town, once farmland, have been swallowed up by housebuilding and other land grabs over the past decade, which continue apace today. This has resulted in a radically changing road layout. See PDF for the general idea .