This railway spur was born out of the need to build the railway from Calahorra to Arnedillo or, more precisely, to transport the coal produced by the Préjano coalmines. Since the main line did not reach the mines but instead passed through Ariñano, some 5 km away, a narrow 60cm gauge mining railway was built to transport the coal to the metre gauge Calahorra railway.
Thus the two railways were born at the same time, entering into operation in 1924. In the early years the mining cars first travelled from the mine heads to the station of Préjano-pueblo. There trains were assembled and pulled by petrol-driven locomotives to the station of Préjano-empalme (or Ariñano), where the coal was transferred into wagons owned by the mining company to take it on to Calahorra.
This situation continued until 1938 when the State took over the running of the Calahorra-Arnedillo railway and the mining company decided to close the stretch between Ariñano and Préjano-pueblo. From then on, the horse-drawn cars would arrive at Préjano-pueblo where the coal was transferred to trucks which took it on by road to Ariñano. There, as before, the coal would be loaded onto railway wagons for the final part of the journey down to Calahorra.
The truth is that coal production from the mines was never exactly abundant (the mining company only ever had two wagons to transport the coal to Calahorra) and the quality of the coal was rather mediocre. There were even attempts to set up a power plant at Ariñano but, somewhat strangely, once completed the plant was immediately dismantled and taken to another region. Finally the last sections of the mining railway were definitively closed in 1966, at the same time as the Arnedillo line