the section of a12 between brentwood and ipswich and previously between great yarmouth and lowestoft, which is now classified as a southern extension of the a47 was classed as a major trunk road, and therefore managed by highways england, whereas the section between ipswich and lowestoft was de-trunked in 2001 and therefore passed control over from highways england to suffolk county council, hence why this section is primarily single carriageway and poorly invested in, therefore the a12 has only now been labelled as a main trunk road between brentwood and ipswich with the northern half after the a14 being deemed a non-primary extension, and a lesser important road.