The numbering system for A-roads, devised in the early 1920s, was based around patterns of roads radiating from two hubs at London and Edinburgh.

[3] It passes through or near north London, Hatfield, Stevenage, Baldock, Biggleswade, Peterborough, Stamford, Grantham, Newark-on-Trent, Retford, Doncaster, Pontefract, York, Wetherby, Ripon, Darlington, Durham, Gateshead, Newcastle upon Tyne, Morpeth, Alnwick, Berwick-upon-Tweed, Dunbar, Haddington, Musselburgh, and east Edinburgh.

[4] It was designated by the Ministry of Transport in 1921, and for much of its route it followed various branches of the historic Great North Road, the main deviation being between Boroughbridge and Darlington.

[8] By the 12th century, because of flooding and damage by traffic, an alternative route out of London was found through Muswell Hill, and became part of the Great North Road.

[15] The inns on the road, many of which still survive, were staging posts on the coach routes, providing accommodation, stabling for the horses and replacement mounts.

Continuing north, the A1 runs on modern bypasses around Stamford, Grantham, Newark-on-Trent, Retford, Bawtry, Doncaster, Knottingley, Garforth, Wetherby, Knaresborough, Boroughbridge, Scotch Corner, Darlington, Newton Aycliffe, Durham and Chester-le-Street, past the Angel of the North sculpture and the Metrocentre in Gateshead, through the western suburbs of Newcastle upon Tyne, Morpeth, Alnwick, Berwick-upon-Tweed, into Scotland at Marshall Meadows, past Haddington and Musselburgh before arriving in Edinburgh at the East End of Princes Street near Waverley Station, at the junction of the A7, A8 and A900 roads.

Scotch Corner, in North Yorkshire, marks the point where before the M6 was built, the traffic for Glasgow and the west of Scotland diverged from that for Edinburgh.

[21] Plans to dual the single carriageway section of road north of Newcastle upon Tyne were shelved in 2006 as they were not considered a regional priority by central government.

[27] It had originally been proposed that the road would be upgraded to motorway from Dishforth to Barton (between Scotch Corner and Darlington), which was the start of current northernmost section of A1(M).

Councils in the north east have called for the section from Hook Moor in Yorkshire (where the M1 link road joins the A1(M)) to Washington to be renumbered as the M1.

[30] In his Autumn Statement on 5 December 2012, the Chancellor of the Exchequer announced that the Government would upgrade a section of road from two to three lanes in each direction within the highway boundary[31] at Lobley Hill (between Coal House and the Metro Centre[31]), Gateshead at a cost of £64 million[32] and create parallel link roads between the Lobley Hill and Gateshead Quay junctions.

This scheme was meant to result in the A1 becoming the A1(M) along the upgraded sections, however the legal proceedings for this did not take place, and instead features a large amount of restrictions, similar to a motorway.

[36][37] A1 Scotswood to North Brunton Upgrade The A1 road, a key route in Great Britain, has seen several major developments in recent years.

Notably, the A1 Scotswood to North Brunton upgrade, completed in November 2022, represents a significant enhancement of the route.

This project, valued at approximately £110 million, added an additional lane in each direction between junctions 74 and 79, covering a distance of five miles.

The upgrade also had a positive environmental impact, reducing carbon emissions by over 8,000 tonnes, thanks to methods such as reusing materials and employing sustainable drainage systems.

[44] The new Grade Separated Junction would allow the A1 and A421 traffic to pass over each other, with a middle level roundabout connecting them together including links to local roads.

As of 2024, National Highways has made substantial progress, including the installation of key infrastructure such as bridges and slip roads.

National Highways, responsible for overseeing roadworks on motorways and major A roads, has outlined plans for continued investment in the A1 to support both local traffic and freight transport.

These upgrades are expected to alleviate congestion, improve safety, and support the economy by enhancing the accessibility of key business and service hubs across the North East.

[48] These projects are part of an ongoing effort to expand the A1 from its current dual carriageway sections into full motorway status in certain areas, a development that is expected to improve traffic flow and reduce accidents.

[49] In response to questions regarding transport in the north, Highways England stated that a new dual carriageway section between Morpeth and Felton and also that of Alnwick to Ellingham would start in 2021 with full opening in 2023.

[50] However in June 2022 UK government minister Grant Shapps delayed a decision about a Development Consent Order signing off on National Highways' plans until December 2022.

[51] Measures were also announced to enhance the performance and safety of the A1 north of Ellingham to include three sections of climbing lanes, five junctions with improved right turn refuges, and better crossing facilities for pedestrians and cyclists.

This will relieve local congestion and provide the capacity needed to make the A1 an alternative (and better) strategic route to the north east.

[31] In 2003 a proposal for a bypass of Sandy and Beeston, Bedfordshire, was put forward as a green-lighted scheme as part of a government multi-modal study, with a cost of £67 million.

[55] It was also announced in 2014 that new technology would be implemented to bring the road to motorway standards, including detection loops, CCTV cameras and variable message signs to provide better information for drivers and active traffic management across Tyne and Wear,[31] while Junction 6 (Welwyn North) to Junction 8 (Hitchin) would be upgraded to smart motorway, including widening of a two-lane section to dual three lanes and hard shoulder running.

[56] A strategic study will examine how to improve the safety and performance of the A1 between Peterborough and the M25, including whether to upgrade the old dual carriageway section to motorway standard.