Harbourfront. Following studies on the feasibility of urban applications of automated people mover systems as feeder transport in the 1990s, a Light Rapid Transit (LRT) line was built between Choa Chu Kang and Bukit Panjang and was opened in 1999. However, this LRT line was plagued with many problems such as damaged guide rails. The subsequent LRT lines built in Sengkang and Punggol in the early 2000s hence used the Mitsubishi Crystal Mover instead; said technology was also adopted for the Changi Airport Skytrain in 2007 to replace the original C-100 system when the system was further expanded to serve the new Terminal 3. Several LRT systems were also planned for many other new towns but were either cancelled or planned as new MRT lines instead. In 2002, construction of the Circle Line, which was previously conceived as separate LRT lines, commenced and was to connect the sub-regional centres of Bishan, Paya Lebar and Buona Vista together. However, construction was impeded by the collapse of Nicoll Highway in 2004 that claimed four lives and injured another three. Operations of the fully automated medium capacity line only commenced in 2009 and the original line was fully completed by 2012. The second medium-capacity MRT line, the Downtown MRT line, was built from 2008 and was opened in stages from 2013 to 2017. In January 2020, the sixth MRT line, the Thomson-East Coast MRT Line, commenced operations. In 2005, the original Sentosa monorail was closed down due to plans to redevelop Sentosa with an integrated resort by 2010. A new Sentosa Express built by Hitachi commenced operations two years later. The MRT system was hit by a series of serious disruptions in the 2010s, the most serious cases occurring in December 2011, July 2015 and October 2017. To address the problems, the government has sought to renew and expand the network as well as expand the workforce in the rail industry. This has included replacement of sleepers, third rail, power supply, signalling and track circuits on the North South and East West MRT Lines, procurement of new rolling stock for existing lines and building of new lines to relieve congestion on the existing lines. The Singapore Rail Academy was also inaugurated in 2017 to better train railway engineers and a new integrated train testing centre is to be built by 2022 to rigorously test new rail technologies. These efforts are starting to pay