By the early 1900s much of the original single track railways in New South Wales had become inadequate for railway operations, particularly the busy Main Lines (South, West and North) through the
Great Dividing Range. Plans were made to duplicate the tracks and at the same time ease the original steep grades and sharp curves, usually all achieved by deviation works. It was a major programme beginning in 1910 and continuing to 1923. The dominant bridge building material was bricks, mostly from the 1912 State Brickworks at
Homebush and mostly in the form of brick arches. This was due to (a) a general lack of expensive imported steel and (b) a long standing government policy to see local materials used as much as possible. Even for short spans, , where a simple steel plate web girder would have been the norm, brick arches were built. The quantity of bricks used in the programme was enormous so the period 1910-23 could be aptly described as the "era of brick arch construction". Thereafter, locally produced steel, from
Newcastle and
Port Kembla, displaced the use of bricks for superstructures, but large quantities of bricks continued to be used for piers, abutments and wings walls. In the duplication programme, that of the Main South was the largest. It had been duplicated to
Picton by 1892, then from 1913 to 1922 duplication was extended to
Cootamundra, a distance of , in sections but not always sequentially. For example the first section from Picton to
Bowral was one of the last completed in 1919 whereas the section, Bowral to
Goulburn, had been completed in 1915. A design policy of the duplication work was to eliminate level crossings, consequently there are as many underbridges and overbridges for roads as there are underbridges for waterways. Fast, safe, through running was to be the new standard for goods and passenger trains. == Description ==