Ordnance Survey - Half-Inch to the Mile, Ministry of Transport Road Maps (1923)
Background
This set of Ministry of Transport Road Maps, issued by the Ordnance Survey in 1923, were the first to accurately show the initial numbered roads. The roads depicted on this set of maps are the Class I (red) roads showing important routes connecting large population centres or through roads, and the less important Class II (green) roads.
The Ministry of Transport was formed in 1919, and following the Roads Act in 1920, the Government was allowed to generate revenue from an excise duty on road vehicles and licenses. With the rapid increase in road traffic, a method for managing the road network was needed. The Ministry of Transport devised a road classification system for this purpose, and a definitive list of road classifications was published in 1922/3.
The Maps
These maps covering England, Scotland, and Wales at a scale of half-inch to the mile (1:126,720) were reduced from larger-scale mapping at one-inch to the mile, primarily the OS One-Inch 3rd edition maps. OS mapping at the half-inch to the mile scale was started in 1903, and the full coverage of Great Britain was completed in 1910. The series was constructed on a Bonne's Projection on the origin 57º30'N, 4ºW. They were published as a set of 34 sheets covering Scotland, and 41 sheets covering England and Wales, with a standard sheet coverage of 48 by 36 miles, the area covered by four one-inch to the mile sheets. There were no contours on the maps, with relief shown just by spot heights. The series was published up until 1936, and the road classifications were constantly revised and updated on later editions of the maps.
Further reading
Roger Hellyer, Ordnance Survey Small -Scale Maps Indexes: 1801-1998 (Kerry : David Archer, 1999)
Richard Oliver, Ordnance Survey Maps: A concise guide for historians. 3rd ed. (London : The Charles Close Society, 2013)
Mike Parker, Mapping the Roads: Building Great Britain (Basingstoke : AA Publishing, 2013)