	The A12 starts just north of the Blackwall Tunnel at a junction with the A102 and the A13. From here to past Ipswich (including the entire section through London) the road is a dual carriageway. North of the junction, the A12 heads northwards as a 2/3 lane dual carriageway mostly at street level. This stretch of road is known as the Blackwall Tunnel Northern Approach. This stretch ends at the triple-layer interchange with the A11 at Bow Road where it becomes the East Cross Route. This is mainly a 3/4 lane dual carriageway built mainly on flyovers and underpasses and was built in the late 1960s, previously called the A102(M).