Highlands History | Picton to Mittagong rail section opened 1919

The route selected for the deviation had a steadily rising grade from Picton, at 552 feet above sea level, all the way to Mittagong at 2027 feet. Whereas the original 1867 section of line followed a rocky ridge between the Nattai and Bargo Rivers, the deviation would be to its east, along a ridge between the Bargo and Nepean Rivers and mostly running parallel with the Southern Road.

Despite labour and equipment shortages due to World War I, construction began in 1915 and included the heavy work of building several tunnels, one 3016 feet long.

A report in the Sydney Morning Herald in February 1916 included the following: "Much excellent road-making has been accomplished in NSW, and no greater tribute could be paid to the skill of those civil engineers who designed the Great Southern Road between Picton and Mittagong, than has been done by the present-day railway engineers in adopting, almost in its entirety, the swath through the primeval bush cut by the pioneer road-makers. The new railway route will, however, interfere somewhat with the road and crosses it about ten times. This has been found to be unavoidable."

The Herald also stated that the deviation, although almost four miles longer than the old line, would secure an improved grade: "On the old line the pull up from Balmoral to Hill Top imposed a great tax on the locomotive, but the natural difficulties would be quite overcome on the new line by taking a wide sweep to the left of the main vehicle road coming from Sydney."

The new line also required a viaduct of considerable length to span the Bargo River. As road travellers had discovered from the 1820s, the river was unpredictable and when it rose they could not cross. A station was built at Bargo and, in 1924, somewhat further along the line at Yanderra where a village developed after a real estate firm began selling residential blocks, although the station eventually closed.

The rail line then wound up through rough sandstone country where apple, pear and cherry orchards had flourished since the 1890s, the station opening there being named Yerrinbool. The rail made a wide sweep through this locality, crossing the main Southern Road at each end of the curve, where arched brick under-bridges were built for road traffic. The rail then entered Yerrinbool tunnel, 811 feet long, and through deep rock cuttings to Aylmerton tunnel, 3016 feet in length, then proceeding through dairy country to Aylmerton station.

The new line continued up to Mittagong where it connected at Braemar to the already duplicated main line to Goulburn. The Bargo deviation's opening in July 1919 completed duplication of the entire Southern Line from Sydney to Goulburn.

On 11 July, 1919 the Sydney Morning Herald announced: "A new railway time-table will be brought into force from Sunday next. On the southern line, the deviation from Picton to Mittagong will be opened for traffic, and the Melbourne expresses and all mail and through passenger trains will run via that route. On the loop line from Picton to Mittagong, via Thirlmere and Hill Top, a local service of trains will be provided, connecting at Picton with main line trains."

While it was railway practice to pull up old lines, the Railway Commissioners had made an exception to allow the deviated Picton to Mittagong section to continue in use for local services after objections had been raised by residents of the small townships affected. Until the 1980s a mixed train ran daily and a rail motor extended to Bowral on three days a week enabling residents along the line to shop. Also a Sunday evening up passenger train ran from Moss Vale to Sydney via the Loop Line.

Although it caused the eventual closure of the loop line, the deviation via Bargo had been an absolute necessity with its smoother gradients and the efficiencies of being a duplicated track. This month marks its 100 years of being an essential component of the Southern Line.