Improvement work to the existing A1 and A1(M) between its junctions with the M18 and M62 in West Yorkshire. The full, official title of this scheme is "A1 M18 to M62 Redhouse to Darrington and Doncaster bypass", which reflects the fact that this work was previously being pursued as two separate projects, one to widen the Doncaster Bypass and the other to upgrade the A1 between Redhouse and Darrington.
The aim of the scheme is to relieve the daily congestion on this length of road and to improve its accident record, particularly on the non-motorway section between Redhouse and Darrington which is an early 1960s dual carriageway with poor horizontal and vertical alignment that forms a link in the national motorway network.
Previous proposals for this part of the A1 involved widening the Doncaster Bypass to provide a third lane from the M18 to Redhouse, and construction of a new off-line dual three lane motorway to bypass the existing road from Redhouse to Darrington. Highways England started a new phase of surveys and assessment work in early 2019 and intend to form new proposals for the improvement work, but it is likely that the result will be a proposal along similar lines. Notably, the A1(M) Doncaster Bypass is not suitable for a typical Smart Motorway scheme in its current form: it is one of the UK's oldest motorways, opened in 1961, and its hard shoulders are not wide enough to convert to a running lane. The road will, therefore, have to be either widened or bypassed.
With thanks to Andrew for information on this page.