In order to cross the coastal mountain ranges of the former Cape Colony, Charles Michell (Surveyor-General, Civil Engineer and Superintendent of Works) and John Montagu (British Colonial Secretary for the Cape Colony) introduced a road building program. Their goal was achieved by the father-and-son combination of Andrew and Thomas Bain, whose civil engineering prowess effected a quantum leap in the quality and range of the road network of the 19th-century Cape Colony.
Thomas served his apprenticeship from 1848 to 1854 as his father's assistant in the capacity of Assistant Inspector of Roads. In this capacity he was involved in the construction of Michell's Pass near Ceres and Bainskloof pass near Wellington. After passing first in the Government examinations in 1854, he was promoted to Roads Inspector for the Western Province. Thomas and his father's careers as road builders continued to be intertwined until Andrew's death in 1864.
Bain built 24 major mountain roads and passes in the second half of the 1800s. His father built eight during the first half of the same century. One of the few passes in South Africa not built by a Bain during that period was Montagu Pass from George to Oudtshoorn, which was built in 1843–47 by Henry Fancourt White, a road engineer from Australia. Bain's first road construction project as newly promoted Roads Inspector was Grey's Pass (renamed Piekenierskloof pass after it was reconstructed in 1958), completed in 1858, that opened up the Olifantsriver valley to the Swartland and the Cape Town market.
One of Bain's major achievements was the construction of the road on the coastal plain between George and the forestry town of Knysna. The project was started in 1867 and took 15 years to complete. This road linked Knysna to the more developed areas towards Cape Town and replaced the dreaded river crossing at Kaaimansgat which early travelers described with trepidation. This project was followed by a series of passes across the Langeberg and Outeniqua mountain ranges. These passes include the Robinson, Tradouw, Garcia and Burgers Passes as well as the Kogmanskloof road. Then followed the 185 km Tsitsikama road, linking the western and eastern portions of the Cape Colony through the indigenous forests of the coastal plain. This road involved the crossing of major ravines, including the Grootriver, Bobbejaansriver, Bloukransriver and Stormsriver gorges.
In March 1873 Bain was appointed as district engineer in the Railway Department. Due to a lack of a suitable candidate to fill the position in the Road Department that he vacated, he rejoined the Road Department after 18 months. In 1877 he became an Associate of the Institution of Civil Engineers.
Bain's crowning achievement was the Swartberg Pass that connects Oudtshoorn, the largest town in the Little Karoo, with Prince Albert beyond the Swartberg mountains in the open plains of the Great Karoo. Construction on the scenic 24 km long Swartberg pass started in 1884 and was completed in 1887. Bain was assisted by another road engineer, John Tassie, who built the last 6 km of the road leading out of the mountain pass into Prince Albert. At the same time, Bain was also in charge of the construction of the Schoemanspoort pass that connects the Swartberg pass with Oudtshoorn. Bain's last road-building project was the construction of Victoria Road in 1887, a coastal road linking Sea Point with Camps Bay and beyond. The route from Cape Town reached it via Kloof Nek, the pass between Table Mountain and Lion’s Head.
In 1888 Bain resigned from the Road Department and accepted the position of Irrigation and Geological Surveyor of the (Cape) Colony. His career with the Road Department resulted in the creation of multiple mountain passes in South Africa. He continued his work in his new capacity until his death. During his tenure he designed and completed the Verkeerdevlei reservoir, amongst other projects.
