Road connecting to the Cross-Harbour Tunnel. A new tunnel was therefore created and given the number 1A. During the modernisation of the line in the early 1980s, Tunnels 1, 3, 4 were removed by demolishing the mounds above them. Tunnel 1A already had double track width when built; a completely new Beacon Hill Tunnel (Tunnel 2) was constructed and took over the original one; and Tunnel 5 was doubled. The new one is known as Tunnel 5A. Rolling stock The line is currently served solely by nine-car R-Stock trains, which entered service on 6 February 2021. Before the introduction of the new R-stock trains, the East Rail line was operated with two types of commuter trains: the 29 refurbished Metro-Cammell EMUs and eight sets of the newer SP1900 EMUs, manufactured by Kinki Sharyo of Japan in 2001. Both models shared the same exterior colour scheme, door arrangement (five pairs per car, except first class), as well as consisting of 12 carriages per train including a first class section. The interior design between the two models is different, and the transverse seating near the ends of the Metro-Cammell carriages has been replaced with longitudinal seating in the Kinki Sharyo models to allow for a wider gangway between compartments. All of the East Rail line Hyundai-Rotem trains are maintained at Ho Tung Lau Depot in Sha Tin. With the construction of the Sha Tin to Central Link, which cannot accommodate trains of greater than nine cars, the MTR decided in December 2012 to phase out all of the aging Metro-Cammell trains from 2020 and replace them with 37 sets of 9-car R-Stock trains built by Hyundai Rotem of South Korea. In 2020, the MTR purchased an additional 6 trains bringing the total number to 43 sets. The first new train arrived in Hong Kong in September 2015 and entered service in February 2021. They fully replaced the older fleet in time for the opening of the Hung Hom to Admiralty section of the Sha Tin to Central Link on May 15, 2022. Due to the shorter train length, there are concerns that the new formation may worsen the existing overcrowding problem. However, the Transport and Housing Bureau and MTRC suggest that the new signaling system and higher train speeds will increase the train frequency from three minutes down to two minutes. It is also estimated that with the completion of the Sha