A Merriwa Railway Line was built from Muswellbrook to Denman in 1915 and then extended to Sandy Hollow and Merriwa in 1917. The section between Sandy Hollow and Merriwa has been closed since 1988. The Sandy Hollow Line between Sandy Hollow, Gulgong and Maryvale,, was originally surveyed in 1860 as a more easily graded crossing of the Great Dividing Range than the Blue Mountains line nearer to Sydney. It was not commenced, however, until 1937, when it began as an unemployment relief scheme of the NSW Government, achieving infamy for having no modern mechanical devices used on it, other than trucks carrying concrete for the 5 tunnels and bridge piers, all other work being done with picks, shovels, hand drills, horses and carts. Construction continued through World War 2 at a desultory pace, held up by money, labour and especially steel shortages, only to be abandoned unfinished, approximately 92% complete, a few years later in 1951. The line crosses the Great Dividing Range by following the Goulburn River and Bylong Valleys from Sandy Hollow to Bylong, with a tunnel under Cox's Gap. The Kerrabee Tunnel, No.1 of 3 in the Bylong range and 1 of 5 on the entire line, that was built under Cox's Gap between 1946 and 1949 was used for eastbound road traffic on the Bylong Valley Way until work recommenced in the early 1980s. It was used in 1978 in the filming of the opening scene for the television series Torque, hosted by Peter Wherrett. In that scene, a Bolwell Nagari driven by Wherrett approached as lights in the dark tunnel, then the camera drew back as the car drove out of the tunnel. The tunnel was also used in a scene in the Australian movie The Chain Reaction The line was opened as a heavy-haul railway to the major coal mine at Ulan in 1982 and extended to Gulgong in 1985 to meet the line to Dunedoo and Dubbo. It is unlikely to be extended to Maryvale.
Current status
Because of Coal from the Ulan Area is now the primary function of this line, Australian Rail Track Corporation refer to the line as the Ulan line all the way from Muswellbrook to Gulgong. Coal from the Ulan, Moolarben, Wilpinjong @ the Western Ulan End and Mangoola, Mt Pleasant and Bengalla Mines close to Muswellbrook also use this line.
In preparation for this, ARTC are upgrading the lines in the Muswellbrook yard and adding two more passing loops to the Ulan line in 2007. More Loops have been added since then as below. The line previously used outdated electric train staffsafeworking procedures in 5 sections over its length. This is being replaced with centralised traffic control in 5 stages. The stages correspond to the 5 ETS sections, numbered from Muswellbrook to Gulgong. The 4th stage, to Ulan, was completed in May 2008. This extends CTC to the westernmost coal mine on the line, covering the majority of train movements on the line. Progress at upgrading the signaling by ARTC was criticised as slow and causing bottlenecks. The upgrade was previously due to be completed at the end of 2007.
Station layout
Ulan has a balloon loop to terminate, load, and return the coal trains up to 1800m long. There is also a crossing loop 900m long. Unlike earlier plans, there are no sidings for general freight, nor any passenger platforms. Wilpinjong, Moolarben, Mangoola, Mt Pleasant and Bengalla also have a balloon loops.
Crossing loops
As of December 2019, there are thirteen crossing loops. The loops are located at:
