Modern Road Construction UK
The great road builders of Britain, unfortunately, packed up shop and went back to Rome in the beginning of the fourth century.
The Roman Empire was in decline, their European borders were being overrun, the legions were needed nearer home, and took with them the engineers, the architects, and the knowledge of road construction.
Their roads remain, in places today as monuments to their construction skills, and it was to take thirteen hundred years before roads of equally hardy construction were built again in Britain.
The fact that they were was down to two separate engineers who worked independently of each other, but between them changed the face of road making forever.
Thomas Telford and John McAdam were both Scottish engineers. Telford, perhaps more a visionary, became involved in many projects including road building.
He was responsible for constructing over a thousand bridges during his laying of almost fifteen hundred miles of new or re-vamped roads in Scotland alone.
His roads were constructed with drainage foremost. The crown allowed run off down a uniformed camber into channelled drainage.
The basis was a 7 inch layer of large rock, a 7 inch layer of broken rock, topped with around an inch of gravel or broken stone over an 18 foot bed, with drainage ditches to both sides.
Telford’s roads were hard wearing, durable constructions, but carried one drawback in that they were considerably more expensive than roads being built by another equally brilliant engineer, John McAdam.
Nevertheless, Telford pioneered many engineering feats, his road built from London to Holyhead crossed the Menai straits to the Isle of Anglesey with a suspension bridge considered one of the greatest feats of iron works ever built.
He built canals, viaducts, aquaducts and became world renown for his contributions to the industrial revolution.
John McAdam pioneered his own method of road construction. He produced a harder surface, but used less substrata of large rock.
As long as there was drainage, and the road surface particles were bound together, the road should be durable enough, he foresaw.
A bed of broken stones laid in a symmetrical tight patterns and covered with small stones created a hard surface, with a gravel type dressing which was worn into the surface by traffic.
Similar technology is still used to this day, but with the advent of advanced construction machinery, (Hanlon CASE) the process of construction is much faster and cheaper in relative terms.
This was the McAdam road, and its economy of construction and adequate durability saw it taken up and adopted by most of Europe and America.
These roads were the precursors of the tar and bitumen binding that would become known as Tarmacadam.