The M16 motorway was the designation planned in the late 1960s and early 1970s for use on Ringway 3, a new

motorway A controlled-access highway is a type of highway that has been designed for high-speed vehicular traffic, with all traffic flow—ingress and egress—regulated. Common English terms are freeway, motorway and expressway. Other similar terms i ...

planned as part of the

London Ringways The London Ringways were a series of four ring roads planned in the 1960s to circle London at various distances from the city centre. They were part of a comprehensive scheme developed by the Greater London Council (GLC) to alleviate traffic con ...

Plan to run a circular route around

London London is the capital and largest city of England and the United Kingdom, with a population of just under 9 million. It stands on the River Thames in south-east England at the head of a estuary down to the North Sea, and has been a majo ...

. Construction of the first section of the M16 began in 1973 between

South Mimms South Mimms is a village and civil parish in the Hertsmere district of Hertfordshire in the East of England. It is a small settlement located near to the junction of the M25 motorway with the A1(M) motorway and is perhaps more widely known because ...

and

Potters Bar Potters Bar is a town in Hertfordshire, England,in the historic County of Middlesex Hertsmere Borough Council – Community Strategy First Review (PDF) north of central London. In 2011, it had a population of 21,882. In 2022 the population was ...

Hertfordshire Hertfordshire ( or ; often abbreviated Herts) is one of the home counties in southern England. It borders Bedfordshire and Cambridgeshire to the north, Essex to the east, Greater London to the south, and Buckinghamshire to the west. For govern ...

and opened in September 1975 with the temporary general purpose road designation A1178. During construction of the first section of the motorway, the majority of the Ringways plan was cancelled and, in 1975 the plans for Ringway 3 were modified to combine it with parts of another motorway, Ringway 4, the outermost Ringway. The M16 designation was dropped and the combined motorway was given the designation M25 which had originally been intended for the southern and western part of Ringway 4.The section of Ringway 3 west of South Mimms

anti-clockwise Two-dimensional rotation can occur in two possible directions. Clockwise motion (abbreviated CW) proceeds in the same direction as a clock's hands: from the top to the right, then down and then to the left, and back up to the top. The opposite s ...

around London to

Swanley Swanley is a town and civil parish in the Sevenoaks District of Kent, England, southeast of central London, adjacent to the Greater London boundary and within the M25 motorway periphery. The population at the 2011 census was 16,226. History I ...

Kent Kent is a county in South East England and one of the home counties. It borders Greater London to the north-west, Surrey to the west and East Sussex to the south-west, and Essex to the north across the estuary of the River Thames; it faces ...

was cancelled and the section clockwise from Potters Bar to the

Dartford Tunnel The Dartford-Thurrock River Crossing, commonly known as the Dartford Crossing and until 1991 the Dartford Tunnel, is a major road crossing of the River Thames in England, carrying the A282 road between Dartford in Kent in the south and Thurro ...

was constructed between 1979 and 1982. The section of Ringway 3 south of the river between Dartford and Swanley was constructed between 1974 and 1977. The South Mimms junction was originally intended to be the end of a short spur connecting the A1 to the M16. The main alignment of the M16 would have continued south-west of the junction towards

Radlett Radlett is a village in Hertfordshire, England, between Elstree and St Albans on Watling Street, with a population of 8,042. It is in the council district of Hertsmere in the south of the county, and is covered by two wards; Aldenham East and ...

and

Bushey Bushey is a town in the Hertsmere borough of Hertfordshire in the East of England. It has a population of over 25,000 inhabitants. Bushey Heath is a large neighbourhood south east of Bushey on the boundary with the London Borough of Harrow re ...

. Evidence of this unbuilt alignment remains in the wide gap between the carriageways to the east of the South Mimms junction which would have been the point at which the spur would have separated from the continuing carriageway.

References

{{DEFAULTSORT:1-0016 Former motorways of the United Kingdom Geography of the London Borough of Enfield Hertsmere London Ringways M25 motorway Motorways in England Roads in Essex Transport in the London Borough of Enfield Roads in Hertfordshire