Junction. The service functioned as a rail-based alternative to the Aust Ferry, which was operated under an erratic timetable determined by the tides, or lengthy road journeys via Gloucester. The rail shuttle service was continued after the end of World War II, but was ultimately made redundant by the opening of the Severn Bridge in 1966, leading to its discontinuation shortly thereafter. Electrification As part of the 21st-century modernisation of the Great Western Main Line, the tunnel was prepared for electrification. While the structure provided good clearances and was therefore relatively easy to electrify, there was also a detracting factor in the form of the continuous seepage of water through the tunnel roof in some areas, which provided a key engineering challenge. The options of using either conventional tunnel electrification equipment or a covered solid beam technology were considered; supported by studies, it was decided to use the solid beam approach. Accordingly, along the length of the tunnel's roof, an aluminium conductor rail was installed to hold an un-tensioned copper contact cable; this rail is held in place using roughly 7000 high-grade stainless steel fixtures, which should be resistant to the hostile tunnel environment. Reportedly, the rigid rail is more robust, requires less maintenance, and is more compact than traditional overhead wires, and has been used in several other tunnels along the GWML. In order to install the overhead electrification equipment, a six-week closure of the Severn Tunnel was necessary, which commenced on 12 September 2016. During that time, alternative means of travel were either a longer train journey via Gloucester, or a bus service between Severn Tunnel Junction and Bristol Parkway stations. Also during that time, and possibly later, there were direct flights between Cardiff and London City Airport. Following the completion of this work, which involved the installation of of copper contact wires using 1,700 vertical drop tubes and 857 anchoring points at a rough cost of £10 million to perform, the tunnel was reopened to regular traffic on 22 October 2016. However, less than two years later, another three-week closure of the tunnel was enacted after it was discovered that some of the recently installed overhead electrification equipment had already started to rust. To combat corrosion, aluminium wire was used, the first of its type in the United Kingdom. Electric trains began operating through the tunnel in June 2020. See also Severn tunnel (1810) Crossings of the