John Metcalf was the first of the great road builders during the Transport Revolution. He was a remarkable man, who had been blind since the age of six, but went on to build about 300 km of turnpike road, mainly in Lancashire, Derbyshire, Cheshire and Yorkshire, in the period 1765 – 1792. His nickname was ‘Blind Jack Metcalf’.
Metcalf believed that a good road should have good foundations, be well drained and have a smooth convex (rounded) surface to allow rainwater to drain quickly into ditches at the side of the road.
Metcalf established his reputation as a road builder, particularly, by building a good dry road across marshland. Other engineers thought it could not be done, but Metcalf accomplished the task by first making a foundation of brushwood and heather. He showed the importance of good drainage, since it was rain which caused most of the problems on the roads.
During the time that Metcalf was working his roads needed no repair and could be used for several years. The fact that Metcalf was blind made his achievements even more remarkable.
Thomas Telford came from Scotland and started work as a stonemason but eventually became one of the greatest of all civil engineers, building canals (Caledonian), docks in London (Menai Suspension Bridge), over 1,200 bridges and well over 1,500 km of excellent new roads.
Telford built many turnpike roads in Scotland, having been commissioned by Parliament to do so, but his greatest achievement was the construction of the 500km long, London to Holyhead road. It was 10m wide and so soundly built, that parts of the road are still in use today on the A5. He took care to avoid steep gradients and sharp bends on his roads. He made the camber across the road gently convex, instead of resembling the side of an orange, as in the older roads.
Telford was very particular about the way his roads were built. Contractors had to carry out the strict requirements of Telford and were carefully watched by a supervisor who had been well trained.
Telford developed a method of road building which required a foundation of heavy stones. The road was then built up with a layer of stones with gravel for the surface. The surface was cambered to encourage drainage. This method made for an excellent quality but it was expensive on materials and labour. The vast majority of trusts could not afford to adopt this method with only limited funds at their disposal.
Parliament commissioned Telford to build a number of roads in Great Britain. In 1815 he was asked to improve the main road between Shrewsbury and Holyhead. Since the 1801 Act of Union with Ireland, Irish MPs had wanted a better route between Dublin and Westminster. Parliament gave in to their demands. Between London and Shrewsbury the road was reasonable, with 29 Turnpike Trusts along the route. From Shrewsbury onwards the road quickly deteriorated as it passed over the Snowdonian mountains. Telford was granted £750,000 to improve this stretch of roads, straighten out bends and improve drainage. To take the road over the Menai Straits Telford constructed a magnificent suspension bridge and it was opened, amid great enthusiasm in 1826. When the road was completed, travelling time from London to Holyhead was reduced from three days to just over one day.
John McAdam, like Telford, also came from southern Scotland. He had long been interested in the mechanics of road-building but it was not until he was nearly 60, that he began to make his name as a road engineer. In 1815 he was appointed surveyor-general of the roads in the Bristol area.
McAdam used a very different method to construct a road than those of Telford and Metcalf. McAdam believed that solid stone foundations were unnecessary. He claimed that a shallow layer (20-25 cm deep) of small stone chips, not larger than 40 mm in diameter, was the best material for ordinary roads, not the larger rectangular blocks of stone or cobbles which were usually used, particularly in towns.
This layer of broken stones (usually granite) knitted together (because of the different edges and angles of the chips) especially when compacted down by the weight of traffic. This caused the road surface to become smooth and hard, making coach journeys more comfortable and letting rainwater run off quickly into drains at the side of the roads.
This ‘macadamised’ surface, as it was called, was cheaper to use than the solid, more permanent methods favored by Telford. The weight of the wheeled traffic on the surface of the road would grind stones down to make a smooth surface. The method was successful and it also had the advantage of being cheap on materials and labour. Therefore, it had a particular appeal to the Turnpike Trusts. Tar was later used to produce the smooth, hard wearing road surfaces we use today – called tarmacadam.
McAdam was made Surveyor-General of the roads in the Bristol area in 1815 and in 1827. Parliament appointed him to the position of General-Surveyor of Roads. He also was the consultant engineer for numerous Turnpike Trusts nationwide.