Steel was an expensive option (requiring importation from Britain) whereas the use of bricks complied with a long-standing policy to use local materials as far as possible to contain costs.

[2] The complex consists of six stone single-track 4 ft 8+1⁄2 in (1,435 mm) standard gauge viaducts and bridges, dated from 1872 and 1916, either in use and extended for double line or abandoned on deviation in 1906.

[5] The single track Main Western Railway reached Sodwalls and Tarana in April 1872 along a more-or-less direct route from Rydal.

[6] Rydal rail underbridges was listed on the New South Wales State Heritage Register on 2 April 1999 having satisfied the following criteria.

[1] The place possesses uncommon, rare or endangered aspects of the cultural or natural history of New South Wales.