comparison to the addition work that would need to be performed to facilitate such rolling stock being operated. There were also some concerns over the tunnel's ventilation being sufficient considering the challenging conditions encountered during construction, but it was believed that these would settle during routine operations without the need for extensive intervention. During 1909, the Gotthardbahn was integrated into the Swiss Federal Railways. On 18 October 1920, the first electric trains were run through the Gotthard Tunnel. Initially, the voltage had to be reduced from the desired to , because the grime deposited on the insulators by the steam locomotives encouraged excessive arcing. However, in May the next year, steam was replaced entirely by electric traction, and the problem of soot and grime was eliminated. During 1932, a memorial for those workers who had died during the tunnel's construction was erected close to the station building at Airolo. The memorial contains a relief produced by Vincenzo Vela from 1882/1883, titled "Vittime del lavoro" (Victims of labour). Until the opening of the Gotthard Road Tunnel in 1980, the Swiss Federal Railways offered car shuttle train services for cars and trucks through the Gotthard Tunnel. Today, that service exists as the rolling highway from the German to the Italian border and aims to reduce truck traffic on Swiss expressways. An improvisational piggyback service from Göschenen to Airolo was offered during the two-month closure of the Gotthard Road Tunnel following a fatal fire caused by a collision in 2001. Neighbouring tunnels The adjacent ramps include several turn tunnels (see Table of turn tunnels). While a triumph of its era and an example of pioneering engineering, the Gotthard Tunnel was considered to be relatively slow to traverse by twentieth century standards, leading to talk of building a superior successor tunnel as early as the 1940s. During 1980, the neighbouring Gotthard Road Tunnel was opened; by 2016, it was reportedly being used to convey around one million freight lorries each year. A second railway tunnel, the Gotthard Base Tunnel, was opened on 1 June 2016 after 17 years of construction; in comparison, it is considerably longer (57.1km; namely the world's longest railway tunnel) and at a about 500 m lower elevation than the first Gotthard Tunnel, enabling trains to traverse the Central Alps on a flat and straight route and therefore more efficiently, at higher speeds, with much less energy consumption, and longer freight