5.1 Road & rail
HEW 705: SO 056 070 to ST 085 950
The Penydarren Tramroad, engineered by George Overton and opened in 1802, has a unique place in railway history. On it, on 21 February 1804, what is generally regarded as the first journey by a steam locomotive was made by a machine built by Richard Trevithick. The L-section cast iron rails were 3 ft long, weighing 56 Ib each, laid on stone blocks to a gauge of 4 ft 4 in. over the out- sides of the flanges. The rails proved too fragile for the weight of the locomotive, so that although the experiment showed the possibilities of this new form of traction it also demonstrated that these could not be fully realized until a much better track became available - which did not happen until 1825, on the Stockton and Darlington Railway.
The Glamorganshire Canal was completed between Merthyr Tydfil and the sea at Cardiff in 1798. In consequence of disagreements between Richard Crawshay, whose Cyfarthfa ironworks were best served by the canal, and the other ironmasters of Merthyr, a tramroad was constructed from Samuel Homfray's Penydarren works to a point on the canal at Abercynon (the Navigation Hotel nearby was once the offices of the Canal Company). This route effectively bypassed part of the canal route, particularly ten sets of locks north of the junction at Abercynon.
From its southern terminus at Abercynon (ST 085 950) the route of the Tramroad runs along the eastern bank of the River Taff. Near Quaker's Yard the river was crossed by timber bridges at ST 094 963 and ST 090 966 (HEW 799). About 1815, these were replaced by segmental, nearly semicircular, masonry arches of 60 ft span and 9 ft wide, which have parallel rings about 18 in. deep composed of 2 to 3 jn. flat stone voussoirs similar to Pont y Gwaith (HEW 800), and indeed, Pontypridd (HEW 27). The old alignment can still be traced.
Further on, the Tramroad was eventually crossed by the Taff Vale Railway on a viaduct (HEW 801, ST 089 965). The section between Quaker's Yard and Pont y Gwaith follows the deep valley of the Taff through pleasantly wooded country.
North of Merthyr Vale the route crosses to the east side of the A470 trunk road and continues to Merthyr where its course is perpetuated in the names of two streets, Tramroadside South and Tramroadside North.
At SO 056 070, near the point of termination, there is a memorial to Richard Trevithick.
HEW 1219: SO 052 057 to ST 190 750
At Pontypridd the River Taff is joined by the River Rhondda before flowing on to Cardiff. Between the two rivers lies the valley of the Gynon, a tributary of the Taff.
At the turn of the 18th- 19th centuries the discovery of iron ore along the heads of the valleys and coal in the valleys led to the establishment of ironworks, as at Cyfarthfa and Dowlais near Merthyr Tydfil, and to a rapid expansion in coal mining. These industries required means of transport for the raw materials and for the finished products. The Glamorganshire Canal from Merthyr to Cardiff was built between 1790 and 1798 to give communication with the sea, but in general the South Wales countryside did not really lend itself to the development of canals, and so there was a great proliferation of horse tramroads such as Penydarren (HEW 705).
By 1830 canals and tramroads were proving inadequate, so in 1835 the Merthyr ironmasters engaged I. K. Brunei to construct the first major commercial railway in South Wales. An Act of June 1836 authorized a single 4 ft 8y in. gauge track, 24^- miles long, with six passing places, from Merthyr, at the head of the Taff Vale, to Cardiff, where dockland development was beginning.
Major works included a rope-worked incline at 1 in 19 north of Navigation (Abercynon); a masonry viaduct at Pontypridd (HEW 1220, ST 071 900) with a skew span of 110 ft across the Rhondda; and the six span masonry viaduct across the Taff and the Penydarren Tramroad at Quaker's Yard (HEW 801). This is unusual in having octagonal piers with deeply chamfered arches. There were three other crossings of the Taff, at Whitchurch and to the north and south of Taffs Well. The southernmost sixteen miles were opened in October 1840 and the line was opened throughout on 28 April 1841.
In the course of time, coal became the dominant traffic. The Taff Vale Railway expanded into the Cynon valley from 1845; by 1856 it had reached Treherbert near the head of the Rhondda Each and in the following year the line to Merthyr had been doubled. Before the end of the century the company had penetrated to Llan-trisant, Cowbridge and Aberthaw and beyond Cardiff to Penarth, where it eventually owned the docks, and to Barry. The railway now had adequate outlets to the sea, but, in spite of some not entirely satisfactory transfer arrangements built at Cardiff, was not able to make use of the broad gauge South Wales Railway (HEW 1191) to move its traffic eastward across the Severn into England until the conversion of that railway to standard gauge in 1872.
The Newport Abergavenny and Hereford Railway Co. exploited this situation to gain a share of the lucrative business by pushing their Taff Vale extension westwards to join the TVR at Quaker's Yard. It was over these routes that there was a massive movement of coal northwards in the First World War to fuel th Navy at Scapa Flow.
The Taff Vale being first in the field, was able to choose the easiest routes m difficult country. Later railways competing for the lucrative coal traffic had to contend with a harsh topography sometimes having to move from valley to valley, and at the expensi of long viaducts and tunnels.  It is little wonder, then, that the surviving lines of British Rail in the area largely use the pioneering routes of the Taff Vale Railway.
HEW 27: ST 074 904
There are a number of engineering works in the vicinity of the Taff and Cynon valleys north of Pontypridd
No study of bridges - and especially masonry arch bridges -would be complete without a reference to William Edwards's famous arch across the River Taff at Pontypridd. His first attempt in 1750, a multi- span bridge, was washed away in a flood after only two years. Edwards then decided to span from bank to bank, but again his arch was washed away in a flood even before the centre was struck.
His next attempt was also doomed to failure. The span 140 ft involved a rise of 35 ft and this meant a great weight of filling over the haunches compared with the crown where there was only the arch ring and the parapets. During the construction of the spandrel walls the excessive weight near the abutments forced the crown upwards and the bridge again coliapsed. Fortunately this was not a sudden failure and Edwards had time to observe the mode of collapse.
Jervoise has described the third and successful single span as follows: 'Edwards then rebuilt the bridge to the same design except that he placed at each end three cylindrical holes graduated in size, the largest being 9 ft in diameter, to relieve the arch from the pressure of its haunches'. The spandrel infilling was of charcoal, for further lightness.
This scheme proved successful, and the bridge, which was completed in 1755, still stands.
The bridge soffit is an almost perfect arc of a circle 89 ft in radius and the arch ring has a depth of construction of only 2j ft. The relatively large rise at the crown resulted in steep slopes at either end of the bridge and this caused serious problems for heavy carts - both during the ascent and descent. A modern bridge has been built alongside and Edwards's masterpiece is preserved and used for pedestrians only. It is 11 ft wide between parapets.
HEW 620: ST077 911
The Berw Road Bridge, which crosses the River Taff about half a mile upstream of William Edwards's masonry arch bridge, is one of several early reinforced concrete bridges in South Wales built on the Hennebique system.
The bridge has a central clear span of 116 ft and side spans of 25 ft. The width between parapets is 26 ft.
The main span has three parabolic arched ribs, at 12 ft centres, cross-braced at intervals. The longitudinal beams supporting the deck are supported by columns off the ribs over the outer thirds of the span and the arch itself serves as direct support to the deck over the middle third.
The side spans have their outer main beams arched to match the centre span.
The bridge was built in 1907 to the design of L. G. Mouehel and Partners. The deck was reconstructed in recent years.
HEW 800: ST 080 975
Pont y Gwaith is a masonry bridge of 55 ft span, 15 ft 9 in. rise, over the Taff about a mile north of Quakers Yard. It has several features in common with Pontypridd (HEW 27), including the use of thin stones to form the arch ring; the severe road gradient; and the narrowing in plan from abutments to mid-span; but has no opening in the spandrels. Both span and width of bridge are much less than those of Pontypridd. There is a noticeable tendency of the arch to be pointed at the crown like the first Ouse Bridge at York. At the present time the bridge is being affected by mining subsidence.
HEW 171: SO 030 076
During the second half of the 19th century the network of railways expanded rapidly in South Wales to handle the vast tonnages of coal being produced. The difficult terrain forced the construction of numerous viaducts, some with masonry arches, some with metal spans. Often of great height and curved in plan, they produced some excellent and sometimes unique examples of bridge engineering. Many have since been demolished and others are disused, such as Cefn Coed, a masonry viaduct which carried a part of the Brecon and Merthyr and London and North Western Joint Railway over the Taf Fawr. It is 770 ft long and 115 ft high with 15 semicircular arches of 39 ft 9 in. and is on a curve. It was designed by Alexander Sutherland in consultation with Henry Conybeare and built by Savin & Ward in 1866.
The line was opened on 1 August 1867 and closed in 1962.
HEW 656:SO 038071
This unique cast iron 'bridge of troughs' still spans the River Taff where it was built in 1793 to carry a tramroad and water supply into the Gyfarthfa ironworks in Merthyr Tydfil.  The designer was the chief works engineer, Watkin George. In 1795 a second bridge, which no longer exists, was cast from the same patterns to an extension of the tramroad from the works to   the bridge, now used by pedestrians, spans 47 ft. Two substantial A-frames, one on each side of the deck, have their feet embedded 'n the river walls, with the apex at mid-span. The frames are held together by rnortice-and- tenon and dovetail joints (George was a former carpenter) and incorporate sockets which carry transverse members at mid-span and at the quarter points. These in turn support the deck structure, which is a closed rectangular box about 2 ft deep and 6 ft 2 in. wide.
Pont y Cafnau undoubtedly had its influence on other, better known, aqueducts. In 1794 the Shropshire ironmaster, William Reynolds, sketched the bridge and in the following year Telford reported that the design and method of construction of Longdon-upon-Tern Aqueduct, itself a prototype for Pontcysyllte (HEW 112) had been referred to Reynolds and himself.
HEW 1055:SO 024 Oil
This steel truss bridge, which carries the only remaining railway line in the Aberdare valley over the Afon Cynon,  played an interesting role in the development of modern design practices and construction techniques.
In the 1960s, the A40 trunk road east of Oxford was bein& widened from single to dual carriageway, and at Wheatley a bridge was erected in 1961 to carry the single-track Oxford to Tharne branch over the new carriageway. It was required to match in general appearance the adjacent rivetted truss bridge over the existing road.
P. S. A. Berridge was responsible for the design and chose to develop a structure which was largely prefabricated by welding, but with the necessary degree of site assembly carried out by Tor-shear bolts, which acted by applying a known pressure to the mating surfaces of the joints.
The experience gained was used in the construction of the much larger trusses, also designed by Berridge, which, in 1962, replaced I. K. Brunei's tubular suspension bridge at Chepstow.
Both bridges were fabricated at the Fairfield works at Chepstow, successors to Messrs. Finch, who did so much work for Brunei.
In 1973, on closure of the Thame branch, the bridge at Wheatley was dismantled and re-assembled near Aberdare. This time the more recently developed Huck fasteners were used for joint assembly.
HEW 371:SN 997 037
This interesting little bridge is certainly one of the oldest surviving 'railway' bridges in the world. In 1811 the Aberdare Canal Company completed a tramway between Hirwaun and the canal head at Cwmbach. The bridge carried the tramway across the River Cynon between Trecynon and Robertstown.
Four arched and trussed cast iron beams spring from continuous cast iron brackets built into the abutments. The width of each truss is only 3 in. and the depth varies from 1 ft at the centre to over 5 ft at the ends. Seventeen cast iron plates 9 ft 11 in. wide make up the total length of deck of 36 ft 8 in. The stone abutments were built with obvious skill.
HEW 804: ST 155 949
The masonry Hengoed, or Maes-y-Cwmmer viaduct, like the iron viaduct at Crumlin (HEW 72) was one of the major structures on the Taff Vale extension of the Newport, Abergavenny and Hereford Railway, and was built in 1857. It has 16 spans of 40 ft semicircular arches and a maximum height of 130 ft. It is built in rough stone, on a curve, and crosses the A469 (spans three and four), River Ryhmney (span seven), and a minor road (span eleven).
HEW 72: ST 213 986
Of all the many viaducts in  South Wales, perhaps the most interesting and   certainly the most dramatic was that at Crumlin.19'20 It is still worth describing although it was demolished in 1966. There is a small model in the National Museum of Wales and traces of the piers can be found on site.
Crumlin Viaduct had ten spans, divided into two groups, of seven and three, by a rock knoll. The total length approached 1700 ft. Grossing the valley of the Ebbw river at a height of 200 ft, the viaduct was built in 1857 by the Newport, Abergavenny and Hereford Railway for their extension to the Taff Vale. The piers
Newport Transporter Bridge each consisted of 12 cast iron columns 12 in. dia. in three rows of four, with an additional raker at each end, covering an area of about 42 ft by 21 ft. Each column was in eight pieces with wrought iron cross- bracing to adjacent columns. There were four lines of Warren truss girders, each of 150 ft span and 15 ft deep, cross-braced by iron plates in 1868 and by steel from 1930. This was the first large scale multi-span use of this design in wrought iron.
The viaduct was designed and built by T. W. Kennard, the partner of James Warren, who devised the truss configuration which bears his name, and which was first used for a major bridge at Newark Dyke, on the Great Northern Railway main line (HEW 1023, SK 801 558).21 The Crumlin columns were cast at his works and the wrought iron, supplied by Blaenavon Works, was fabricated at site and hoisted into position.