A talk given by Mr. A.S. Whittaker (member) at Green Hills, Worthing on 9th May, 1983
With the President in the chair we were given a comprehensive dissertation on the U.K. motorway system by an engineer who had participated in the project from the very beginning, with particular involvement in the midland areas.
The Special Roads Act of 1949 set up the motorway programe but prior to that James Drake, the entrepreneurial Lancashire County Surveyor, had set up a team which produced the Road Plans for Lancashire based on the future motorway system (M6, M6l, M62, M55, M65, M580) as well as the link roads. Alan Whittaker expressed his good fortune to be a member of the team; the experience of taking part in such a comprehensive report, and the public discussion and consensus which followed, proved very valuable as he moved to Monmouthshire, then Yorkshire and in 1956 to Warwickshire.
Here, the imminence of the Ml/M45 motorways caused quite a stir, for example, the last bridge building had been in 1938, and Alan was given the task of setting up a new section to design and complete the 6.5 KM Menden By-pass and to prepare the Warwickshire length of the M45. Start of survey and design in August ’56, out to tender April ’57 and completion was in 13 months. At the same time the A45 from Birmingham City Boundary to its join up with the M45 was upgraded to dual carriageway, all to be opened with the Ml in 1959.
During the progress of the M1/MA5 there had been disagreements with the Ministry of Transport on some details; their insistence on open drainage across the hard shoulders and down embankments, the limited construction of hard shoulders and the use of as-dug gravel for sub-base. W.C.C. had always made extensive use of the high quality stone available locally, providing good drainage, but M.O.T. took advice from the Road Research Laboratory to use gravel in 112 KM of motorways with considerable savings. The speaker insisted that the sub-grade be kept dry and equally important that bridges be waterproofed. He ensured that all bridges in Warwickshire were waterproofed but many on MI/M45 relied only on asphalt wearing surface over the bridge deck concrete, in the belief that concrete properly laid was waterproof.
The Inadequacy of free flow drainage was shown by deep ruts forming on the hard shoulders of Ml/M45 due to heavy lorries, so the M.O.T. specification was changed to extend the carriageway to include the shoulder, although to less construction depth, and to provide controlled drainage. This was applied on Ml and M6 as they proceeded and retrospectively on parts of Ml and M45. Alan provided a consultative role with the M.O.T. for the M6 but the main task of the Warwickshire team was provision of access from major roads to all the junctions e.g. A26, A46, A444, A446 and A452. He explained to us the problems with the A446 around Coleshill where a plan he devised in 1959 was not adopted because of M.O.T. prevarication, this plan was later blocked by the construction of the British Gas Lurgi plant so that M.O.T. pinned their faith on the M42 northwards route now under construction.
The layout of motorways in the Midlands is essentially an H format comprising M5/M6 and M6/M1. A double cross-over format had been considered but the M.O.T. decided against it on grounds of cost and speed of implementation. It was rapidly becoming obvious that the H was inadequate. Alan spelt some aspects out to us and the Warwickshire engineers continued to push for implementation of a double crossover. They supported the principle and general line of route but not certain local aspects. Unfortunately the M.O.T. became inflexible with these minor aspects which should have been settled prior to the public enquiries. The SW to NE link of the crossover emerged in the M42, now partly built and otherwise mostly under construction.
From 1971 traffic figures showed rapid increase in heavy goods vehicles as well as cars. M.O.T. and R.R.L. had reduced their requirements for road thickness, from the rule of thumb of at least getting below the frost level of 440 mm. New design and construction was based on one million standard axles of 8 tonnes and expectation of lives of 20 years for asphalt and 30 for concrete. Warwickshire engineers were not convinced and stuck to their tried design for trunk roads so having, at least, foundations good for 20 years.
Within 5 years of opening M6 to the NW, congestion was causing motorists to use trunk roads as reliefs with consequent increase in deterioration, the A444 suffered embankment slips, rutting and transverse cracks in the slow lanes and, even worse, longitudinal cracks. Patching did not last long and, as similar problems arose on the M6 at Stafford the speaker set up a team to prepare contracts, supervise and monitor remedial work on the whole of the M6 through Warwickshire. Work to improve drainage included total reconstruction of three lane carriagways for the worst areas or half middle lane plus slow lane and for the remainder, where headroom permitted, an overlay of 200-250 mm of asphalt. On viaducts and bridge decks damp-proof courses and joints were protected and/or removed.
To carry out this work contraflow traffic control at 80 KM/h came into use. The limitations as to temperature at which laying is allowed and the need to avoid certain sensitive times, e.g. motor show and cup finals, leads to periods of frustration for road users. Eventually a maximum contraflow length of 3.2 KM with a minimum of 9.6 KM between contracts was adopted. From August ’77 to 1985 about 34 KM of M6 has been strengthened with two contracts for completion by 1987.
Warwickshire were allowed by M.O.T. to use their own specification for the sub-base and to increase the depth of the road base. Recently research and cutting back by M.O.T. and R.R.L. reduce deflectograph probability factor from 0.9 to 0.5, in a period when HGV daily figures are still rising – on M6 from 10,986 in 1977 to 16,500 in 1984. The speakers previous colleagues consider this retrograde and will lead to less than 20 years life. The main causes of failure appear, as before, poor embankment material, inefficient drainage and cracking of the original lean concrete base into 10 – 12 slabs. Concern arises also from overloading, which occurs in spite of M.O.T. weighing bays and the mobile weight testing units which can be set up quickly on the hard shoulder.
Many senior engineers do not consider the motorway program finished on completion of M25 as stated by Government. The obvious overloading on many, e.g. Ml, M5, M6, M67 in a year when the M.O.T. programs of reconstruction is 128 KM at £140 million does suggest some alternative motorway routes will be essential. Some likely examples of relief were given and reference made to routes for the 21st century including, in this area, the extension of the M27 from Havant to Dover incorporating by-passes for Brighton and Worthing.
The talk was illustrated by large maps of the motorway system and by sectional drawings of different constructions.
A very lively discussion followed but had to be curtailed through shortage of time. In answer to a question about estimates (E.L. Jones) Alan said first estimates were on a cost per mile basis, then more detailed and finally from quantities. The Surveyors Department, updated for inflation.
The contractor in effect decides whether concrete or asphalt by virtue of price and, of course, the relative costs depend on location. Concrete surfaces are expected to give 30 years life but with more cement 40 years, but joints are still a drawback. In answer to D.R. Fife he said the slow lane is worst for wear damage because of heavy axle loads, even though speeds lower, but Warwickshire saved here because of their stronger base. L.G. Hill said concrete is not resilient so will crack and absorb moisture so why not use a resilient surface on a main support system to which the speaker said foundations were the cause of the problem – e.g. brick hardcore before the sub-base. In answer to J.J. Thomas it was said that one heavy goods vehicle is as damaging as 600,000 cars. L.A.E. Fosbrooke asked about aerial surveys to be told that they were useful in cities but not much used for road planning, for example the Ml was based on ordnance surveys and Warwickshire carried out their own surveys. N.H. Taylor proposed the vote of thanks and asked about M.O.T. specifications and queried whether they had made prior enquiries about overseas experience in motorway construction. He said suffering failures is one way of learning but some troubles are due to mistakes. Perhaps consultation could have avoided some troubles. He expressed the appreciation of the meeting for a most interesting talk which undoubtedly meritted a much larger attendance. All present gave enthusiastic