For a few hundred metres, it now runs to the right of the considerably narrower road on Vignoles rails, until the line reaches the former halt of Chur-Sassal, which was abandoned in 2001.

Over its whole length, the line climbs a total of 1,155 m (3,789 ft) in elevation and crosses the Plessur once and the Schanfiggerstrasse (Schanfigg road) three times.

The five intermediate stations of Lüen-Castiel, St. Peter-Molinis, Peist, Langwies and Litzirüti are served before the line reaches the terminus of Arosa on the Obersee (upper lake), 25.681 km (15.957 mi) from Chur.

It was planned to run the line along the cantonal road after it was widened with some sections on separate track through tunnels in difficult places.

The Chur engineer Robert Wildberger and his colleague Englert applied for a concession for the construction of an electric railway to Arosa in January 1903.

It put forward three different options, with the first involving a 23.4 km (14.5 mi) line running on the left side of the Plessur.

The latter two options provided for rack railways to overcome the slope, which was expressly not recommended by the chief engineer Moser of Zurich, who had been commissioned by the municipality of Arosa.

All three proposals began at the Chur station forecourt, headed west and crossed the Plessur near the Welschdörfli district, ran under the Rosenhügel through a 500 m (1,600 ft)-long tunnel and had their first stop at Bodmergut.

The core of this 32 km (20 mi) project was a tunnel connection under the Urdenfürggli and the Hörnli mountains to the Wasserboden lake at an altitude of 2,100 m (6,900 ft).

It was followed by a protracted competition between the Wildberger & Co. project, which was revised again and favoured by the Schanfigg valley communities, and the proposal of Ahlsfeld & Spyri, which initially also found the support of the city of Chur.

After a conference to determine a way forward in December 1909, the Chur city council supported the project of Wildberger, which also caused a change in opinion in Arosa and led to a withdrawal of the Churwalden line's application for a concession.

Nevertheless, an engineer from Chur, Versell, proposed a new, 24 km (15 mi) option, the so-called Lenzerheidebahn via Malix, Praden, Tschiertschen and under the Ochsenalp to the Obersee.

Gustav Bener, who had been commissioned as chief engineer, and the Wildberger company resolved outstanding issues and presented plans to the Grisons government for approval on 4 March 1912.

The unstable terrain made site management difficult, causing the original opening date of 15 November 1914 to be postponed.

The construction of the Lüen power plant, which was intended to supply both the railway line and the city of Chur with electricity, was not allowed to fall behind, unlike the other works.

In addition to the difficult terrain, preparations for the general mobilisation at the beginning of the First World War also caused serious problems, as various construction workers and engineers were drafted for military service.

The ChA used a different electrification system for its blue and white rolling stock than the neighbouring Rhaetian Railway, namely the rare voltage of 2400 volts DC.

As part of this, consideration was given to converting the Arosa line to single-phase alternating current and the Ge 4/4 I main network locomotives that were under construction were modified for the possible new application.

After the Second World War, three new three new substations with rectifier systems were built to improve the power supply in Chur-Sand, Lüen-Castiel and in the Haspel mine.

The project, which would have been built during the planned conversion of the Arosa railway to 11 kilovolts AC, had to be abandoned in the autumn of 1996 due to the withdrawal of a guaranteed federal contribution.

The Sand substation, which feeds the contact wire between Sassal and Arosa, is also supplied via a cable in the river bed of the Plessur.

As a result of a newly developed system of overhead wire, suspension and power supply, costly construction measures in tunnels and cuttings—in particular the lowering of the track—were kept to a minimum.

The total modernisation costs, including investment in rolling stock and the extension of the passing loop at St. Peter-Molinis station, amounted to CHF 58.3 million, 96 per cent of which was borne by the federal government.

Due to a parliamentary initiative, Amberg Engineering AG prepared a preliminary project for the construction of a tunnel between Litzirüti and Davos in 2010 on behalf of the government of the Grisons.

Following the partial collapse of a side wall as a result of water inflow on 3 April 2009, a replacement of the Partusa bridge at Peist was planned and built in 2010.

[16] On Good Friday, 29 March 2013, rocks fell on the railway again at the east portal of the Lüener Rüfe tunnel over a length of about 100 m (330 ft).

In addition to clearing, the extensive safety measures included the demolition of two unstable rock spires in the area affected.

Loose rubble was also removed using earth-moving equipment and certain rock areas were covered with a net under tension before the actual repair of the railway facilities commenced.

[23] The costs of repairing the two rockfalls and the damage caused to the railway track amounted to around CHF 3.8 million, most of which was borne by the federal government and the canton of the Grisons.

[30] Wet fresh snow on 23 October and 6 November 2014 caused damage to the catenary between Litzirüti and Arosa and St. Peter-Molinis and Peist.