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A(1)M Part of the A1 Strategic North - South Link

The archive includes the motorway from Junction 1 with the M25 in South Mimms to Junction 10 north of Baldock, length 23 miles and the length of 14 miles between Alconbury and Peterborough from Junction 14 to Junction 17.

Why has the A1 Great North Road not been improved to motorway status over its full length of some 400 miles, when it is a major north-south artery between London and Edinburgh? This appears perplexing, particularly as a scheme for a national motorway system submitted by the Institution of Highway Engineers to the Ministry of Transport in 1936 included a motorway between the north side of the London Orbital Motorway to the north of Hull as well as a motorway from the northwest side of the London Orbital Motorway to Leeds and Newcastle-upon-Tyne. The answer could be said to be 'expediency'. The Minister of War Transport, the Rt. Hon. Alfred Barnes, announced in the House of Commons in 1946 the Government's proposals for a network of principal national roads incorporating 800 miles of motor roads and improvements of existing roads incorporating by-passes of urban areas, but generally with improvement in their present alignment. The A1 was shown in the latter category. This had the advantage that relief from traffic congestion by the construction of by-passes and improvements could be started without recourse to new legislation required for restriction of categories of vehicles and access on motorways. However, the policy of by-passes and on-line improvements had the disadvantage that smaller communities which were not considered to merit a by-pass still had to endure the heavy traffic on this important artery.

In May 1956, Rt Hon. Harold Watkinson, Minister of Transport and Civil Aviation, pronounced that the Government intended to transform the A1 into a major north-south road link designed to cope with modern traffic conditions. The preparation of schemes for the provision of dual carriageways to replace the existing narrow and winding single carriageway lengths of the A1 was allocated to County Councils as Agents to the Ministry.

In Huntingdonshire, for example, the programme consisted of the provision of a dual carriageway for 28 miles of the A1 Great North Road from Eaton Socon, west of St Neots, to the River Nene at Wansford, north-west of Peterborough. The earliest length to be completed was the 5½ miles from Alconbury Hill, north-west of Huntingdon to the B660 road, near Conington. It was opened to traffic in 1957 and incorporated a unique constructional experiment by the County Council in conjunction with the Roads Research Laboratory of the Department Scientific and Industrial Research. This extended over 2½ miles of the northbound carriageway and has provided most useful basic data on the performance under traffic of a wide range of thicknesses and strengths of the layers of rigid and flexible road pavements.

Stilton Bypass, south of Peterborough, opened to traffic by Rt Hon Harold Watkinson on the 21st July 1958, was the first bypass to be completed on the A1 subsequent to the Minister's pronouncement. This section of the ancient Roman Road, Ermine Street, and later post-road between London, York and Scotland, has the added distinction of being part of the route on which the first Turnpike Road Act of 1663 applied, with Stilton one of the first three locations authorised for the collection of tolls in the Act.

The earliest length of the A1 to be opened as a motorway, following the procedure laid down in the Special Roads Act 1949, was Stevenage Bypass in May 1962. Its length is 7 miles, with Hertfordshire County Council as Agent Authority, Main Contractor Martin Cowley with a tender price of £1.8 million. This was followed by Baldock Bypass in July 1967, also 7 miles long, with Herts C C as Agent Authority, Main Contractor A Monk with a tender price of £3.5 million.

In 1959, the Government decided that improvement of the A1 between South Mimms and Welwyn should be examined as a whole and in 1962 the Minister of Transport announced that this would form a continuous motorway. The A1 (M) Lemsford - Welwyn length of 3 miles was opened in May 1973 under the aegis of the Eastern Road Construction Unit (Herts Sub-Unit), Main Contractor A F Budge, tender price £2,2 million. The length of 3 miles between South Mimms and Roestock, south of Hatfield, was opened in May 1979, also under the aegis of ERCU (Herts SU), Main Contractor Higgs and Hill, tender price £3.6 million.

Roestock to Stanborough

This left the length of 3 miles of the A1 between Roestock and Stanborough.  This section of Al is part of the original Barnet By-Pass which was built in 1925-27 and the length between Roehyde (A405) and Oldings (A414) carries traffic from the North Orbital Road in addition to long distance north - south and local traffic.

After the publication in July 1972 of the Urban Motorways Committee report "New Roads in Towns" the proposals were reviewed. That review led to three "on-line" and two western bypass alternatives being identified as possible improvements between Roestock and Stanborough.  The public were consulted in 1974 to obtain their opinion of these alternatives and also to invite comment on the need for improvement and to elicit any other proposals. The scheme was one of the "on-line" alternatives and it was selected as the Department of Transport's preferred scheme in 1977.  It was the subject of a Public Inquiry in 1981 at which the details of the project and its effects were described, and objections to the scheme were presented, some of which resulted in amendments being made to the scheme as presented. The revised scheme is that which was built.

What was described as the "Hatfield Project" was an overall concept - Road and Redevelopment.  The aim was to create an acceptable solution to a difficult problem, which would overcome the conflicting demands of highway, environment and local needs. The overall concept had been to create a scheme which offered the opportunity to revitalise and replace the infra-structure of the District at the same time as solving the very obvious traffic problem in this largely urban environment.  Hence, a partnership involving both the public and private sectors, was brought together to bring to fruition a suitable scheme.  The final link in achieving this overall Concept was therefore the selection by the District Council of a development partner.

The Department of Transport, the Hertfordshire County Council and the Welwyn Hatfield District Council worked closely together during the project conception. The chosen scheme included, on environmental grounds, a 1150 metre long tunnel and in so doing created a redevelopment area of some 25 acres of land on the western side of Hatfield only ½ mile from the town centre.  Work started In the spring of 1983.  At Hatfield this initially involved alterations to gas, electricity and water mains, sewers and telephone equipment, and demolition of buildings. These was necessary to enable road construction to proceed unhindered.

Hatfield tunnelOn April 2nd 1984 Tarmac National Construction (now Carrilion Construction) started road construction work under contract to the Department of Transport. This work was supervised by Hertfordshire County Council.  On October 26th 1984 W.H. Smith and Company Electrical Engineers Ltd were appointed to supply the electrical and mechanical services for the tunnel, the work being supervised by Mott Hay and Anderson Electrical and Mechanical Services.

The advance Works included numerous public utilities' services which followed the route of the existing A1 through Hatfield which is close to the new motorway and crosses it twice.  Large scale alterations were necessary to the public utilities' apparatus to enable the new road to be constructed. As far as possible these alterations were carried out in advance of the road construction.  The alterations to the public services were co-ordinated by Hertfordshire County Council and were carried out by the various service authorities, British Gas, Eastern Electricity, Lee Valley Water Co., Welwyn Hatfield District Council (its sewerage agent to Thames Water Authority) and British Telecom.

The built-up area on the line of the motorway, between Cavendish Way and Birchwood was demolished by Kimbell Construction Ltd in advance of the road construction. This was done to avoid the potential disruption to construction work due to unforeseeable difficulties in the demolition of a large built-up area.  The contract also included the erection of a temporary noise barrier along the eastern boundary of the demolition area. This barrier remained during the road construction period to screen the adjacent houses from the construction work and was removed after construction of the motorway was completed.

The motorway is entirely at or below ground level. The major cutting is from south of Cavendish Way to Birchwood, and this cutting is the site of the tunnel and its approaches. The motorway is also in cutting where it passes under Roehyde interchange.  The interchanges are on embankments above motorway level.  

Excavation totalled 900,000 cubic metres of which 390,000 cubic metres were placed in embankments and a further 80,000 cubic metres used as filling for landscaping and other environmental improvements, including the construction of noise mounds to protect adjacent properties from the effects of the completed motorway.

In addition to the disposal of water which falls upon the road surfaces, the drainage scheme involved the lowering of the ground water level at the site of the tunnel.  The permanent ground water drainage system consisted of a grid of filter drains below the motorway which discharged to a pump chamber behind the cast abutment of the tunnel at the Southern Sub-Station. A separate drainage system to collect water from the motorway surface in the tunnel also discharged into that pump chamber.

Water from the motorway cutting at Roehyde was also collected in a pump chamber situated within the interchange roundabout on the west side of the motorway.  Water from the tunnel pump chamber is pumped to the Roehyde pump chamber. From there, together with the water from the adjacent motorway, it is pumped to an outfall into the Ellenbrook.  In fact, all water from the motorway and all-purpose roads between Roestock and the north end of the tunnel discharges into the Ellenbrook. However, discharge to the brook had to be limited to not more than 75 litres per second. To achieve this all water first passed into a balancing pond, either via the pumps at Roehyde or directly from gravity drains.   The capacity of the balancing pond is 1,200 cubic metres and the outfall from the pond is designed to pass a flow of 75 litres per second when the pond is full.

Water from the northern approach to the tunnel collects in a pump chamber adjacent to the north portal of the tunnel; discharge from the pumps is piped some 1,600 metres to an outfall into the River Lea. The motorway and all-purpose roads at the northern end of the scheme discharge by gravity to the River Lea.  To prevent pollution of the water courses by oil or other chemicals which might be spilled on the highway, Ellenbrook is protected by the balancing pond which is designed to act as an oil trap. It also has a penstock by which the outfall can be closed if pollutants which are miscible with water should be spilled on the highway.  The River Lea is protected by an oil trap which also has a penstock to close the outfall.

The 1150m long Hatfield Tunnel is a cut-and-cover structure constructed east of the existing A1 between Cavendish Way and the Green Lanes Roundabout. The tunnel accommodates the full motorway formation width with a continuous separating wall along the motorway centre line. Raised walkways along both sides of each carriageway accommodate the extensive cabling and service ducts required for tunnel services and motorway communications.

The construction of the tunnel is of traditional reinforced concrete, the roof, walls and foundation bases being continuous to form a two bay portal. The tunnel is founded on the glacial gravels with spread footings, but where additional heavy loads from the development structures affect the central wall its foundations are strengthened locally by insitu bored piles founding in the hard chalk sub strata.  It is estimated that nearly 10,000 tonnes of reinforcement and over 80,000 cubic metres of concrete were used to construct the tunnel.

Tunnel Services include power supplies, lighting, ventilation, environmental control, plant monitoring, pumping, communications, fire fighting, security and traffic surveillance. Automatic control systems will continuously monitor and report to central control and maintenance on the operational state of the plant and information transmitted and were stored on a computer.

The tunnel is longitudinally ventilated by 52 jet fans in each bore, located above the walkways at roof level and automatically controlled.  Panels at 39m intervals on the nearside walkway, provide emergency telephone facilities connected to police control, and automatic fire hose reels. Radio aerials for emergency and maintenance services are mounted in the tunnel roof.  Closed Circuit television System is provided in each bore of the tunnel and is remotely controlled from Police Control at Hertfordshire County Police HQ at Stanborough.

Sensor loop systems in the carriageway surface at intervals throughout the motorway detect vehicle movements. The data obtained is used to provide the police control room with information of traffic flow patterns and potential problems.

Green Lanes roundaboutApart from the tunnel, there are 12 other structures in the scheme plus extensive retaining wall construction through Green Lanes Roundabout.  There are 6 subways, 2 footbridges and 4 large road bridges over the motorway. All of the structures are of traditional reinforced concrete except for the OIdings Interchange bridge where the bridge was built on line with the necessity to keep the Al open and running. This requirement precluded temporary shuttering for an insitu concrete deck, thus precast prestressed concrete `U' beams lifted into position under a short-term temporary closure of the A1 formed part of the main span of the bridge.

 The route of the new motorway necessitated the demolition of over 200 properties, many of them commercial, but on completion the land above the tunnel was again made available for development together with areas immediately adjacent to the tunnel line which were acquired by Welwyn Hatfield District Council, so bringing the entire area into public ownership.

On June 12th 1984 the Welwyn Hatfield District Council unanimously selected as their development partner the Carroll Group of companies who put forward the futuristic Park Plaza plan.  With the comprehensive leisure theme which is the underlying feature of the scheme the focus of the proposed development was a 200,000 sq ft. glass covered shopping area situated over the southern section of the tunnel and containing a variety of leisure orientated retail units. Included in this totally new retail concept is an ice skating rink, restaurant, exhibition and activity areas. Covered ways link this centre to a 100-bedroom prestige hotel, enclosed garden centre and further open leisure activity areas. The proposed scheme also contains a small residential zone and a prestige office development at the northern end of the site.

Alconbury (Huntingdon) to Peterborough

 A1(M) Alconbury to PeterboroughThe other length of the A1 in the Eastern Region which has been improved as a motorway is on the Alconbury to Peterborough stretch, opened in October 1998 by Lord Whitty. This follows the corridor of the Stilton Bypass which catered for all-purpose traffic, but moves the alignment eastwards away from the village.

This improvement to motorway standard was needed primarily for safety reasons. It was the busiest length of the A1 which had not been raised for motorway standard. In 1961 it carried over 50,000 vehicles a day, of which about 1 in 5 were lorries; there was extensive congestion at peak times with regular queues of traffic up to five miles long; traffic was expected to double over the next 30 years; existing side road and property accesses were a source of danger to local and through traffic.

The total length of motorway is about 14 miles, with four lanes northbound and southbound, each with hard shoulder between Alconbury Hill and Norman Cross. Safety for through and local traffic is improved by the provision of a separate local road system.

Tenders for the project were invited in May 1995 under the new procedures on a "Design Build Finance and Operate" basis over a 10-year period. Tenders were returned by February 1996 and the successful tenderer, (Road Management Services, a joint venture of AMEC, Alfred McAlpine, Brown & Root and the Spanish firm Dragados) was appointed in April 1996, with work starting in May 1996.

Under the terms of this "DBFO" contract, payment is made in stages over the 30-year period based upon automatic continuous counting of the number of vehicles (shadow tolls). There is no stopping of vehicles and no payment of tolls to the drivers of vehicles it will be no different from a conventional motorway. The contract embodies performance incentives to provide a high level of service, ensure liaison with interested parties and protection of the environment. This private financing has enabled the upgrading of the A1 to take place earlier than would be possible under previous public financing arrangements.

Contract details:

Section Length Engineer Contractor Cost
South Mimms to Roestock (J1 to J2) 3m Herts Sub-unit Higgs & Hill £3.6m
Roestock to Stanborough (J2 to J4) 3m Herts CC Tarmac (now Carrilion Construction) £36.9m
Stanborough to Welwyn (J4 to J6) 3m Herts Sub-unit A F Budge £2.2m
Stevenage By-pass (J6 to J8) 7m Herts CC Martin Cowley £1.8m
Baldock By-pass (J8 to J10) 7m Herts CC A Monk £3.5
Alconbury to Peterborough (J13 to J17) 14m DBFO contract: AMEC, A McAlpine,Brown & Root & Dragos ?