Circle MRT Line

History

Plans for the Circle Line date back to the 1980s. The then Minister for Communications and Information, Dr Yeo Ning Hong stated that such a system "would be feasible when the population reaches four million."

The Circle Line was first known as the Marina Line in May 1998. The Marina Line was initially planned as a 12-station underground line, starting from Chinatown and Dhoby Ghaut via the National Stadium to either Kallang or Paya Lebar station. However, the Chinatown leg was later truncated and was reduced to 6 stations up to Stadium station. On the other hand, a further extension towards Upper Paya Lebar was added in the year 2000. The Marina Line was also merged with an LRT line that goes from Paya Lebar to Buona Vista via Serangoon and Bishan to form Circle Line Stage 3 and 4 in 2001. Circle Line Stage 5 was finalised in February 2002 when Stage 4 was extended from Buona Vista to World Trade Centre to close up the link and to provide connectivity from the west to Sentosa, and it became the full Circle Line in the end. Stations in Circle Line that were a part of the original Marina Line plans include Dhoby Ghaut, Bras Basah, Esplanade, Promenade, Nicoll Highway and Stadium. Also, the part of the Marina Line from Chinatown to Promenade is now part of the Downtown Line.

Construction started in April 2002, and was supposed to be opened from 2006 and fully opened in 2010, with an estimated cost of S$6.7 billion, but the Nicoll Highway collapse caused the construction of the Circle Line to be delayed to open from 28 May 2009 (the Stage 3 of which it is not affected by Nicoll Highway collapse), with full opening on 8 October 2011, at an escalated cost of nearly S$10 billion. Due to the re-alignment of the Nicoll Highway Station to a new location, the station is only two-thirds the size of the original plan before the collapse, and located 100 metres (330 ft) away from the highway collapse site. The decision was also made to open both Caldecott, and Haw Par Villa stations (previously Thomson and West Coast), as a normal stations leaving the Bukit Brown MRT Station closed, and there is only a middle track and emergency escape shaft.

Stage 3, a 5 kilometres (3.1 mi) five-station segment stretching from Bartley to Marymount, was the first section of the line opened, on May 28, 2009. Initial ridership on this section was lower than estimated, at 32,000 passengers per day (ppd) instead of the estimated 55,000 ppd. Tunneling works for the entire line were completed on August 17, 2009. Stages 1 and 2 started operations on April 17, 2010, Stages 4 and 5 on October 8, 2011, and the final Circle Line Extension on January 14, 2012. The line was also fully completed in October 2011, to commemorate operator SMRT's 24th anniversary.

Circle Line Stage 6

On 17 January 2013, the Land Transport Authority (LTA) announced 'Circle Line Stage 6' which will finally close the circle, running between Marina Bay and HarbourFront. This extension will help commuters who want to go from Harbourfront to Marina Bay or vice versa. It will be a 4 km extension. On 29 October 2015, the LTA announced the 3 station locations for the 'Circle Line Stage 6'. The stations are Keppel Station, Cantonment Station and Prince Edward Station. Tenders were called for construction in 2016 and demolition, diversion and utility works commence this year in 2017. Construction of the line will begin earliest in 2018 and it is due for completion in 2025. When the three CCL6 stations: Keppel, Cantonment and Prince Edward are completed in 2025, the CCL will have a total of 33 stations, including 12 interchange stations with other MRT lines.

Nicoll Highway collapse

On 20 April 2004, a section of the tunnel being built for the Circle Line collapsed, apparently when a retaining wall used in the tunnel's construction gave way. This occurred near what was planned to become the Nicoll Highway Station on the Circle line, not far from the Merdeka Bridge. The accident left a collapse zone 150 metres (490 ft) wide, 100 metres (330 ft) long, and 30 metres (98 ft) deep. Four workers were killed, with three more injured.

A criminal inquiry found the main contractor Nishimatsu Construction Company and joint venture partner firm Lum Chang Construction Company and their officers, as well as key Land Transport Authority officers responsible for the collapse. Several other officers and subcontractors were reprimanded and issued warnings in connection with the accident.

As a result of this accident, the first phase of the Circle Line, previously scheduled to open in 2008, was completed in 2009 instead. The affected station has been shifted about 100 metres (330 ft) away from the accident site and is now located at Republic Avenue.

This accident had also resulted in stricter safety regulations for the construction of all future MRT lines. The shifting of the Nicoll Highway Station also meant it can no longer serve as a terminus for the Bukit Timah Line, partially influencing the creation of the current Downtown Line.

Other incidents

On 16 August 2007, the Building and Construction Authority (BCA) issued a stop-work order and revoked the contractor's tunnelling permit after a 7 metres (23 ft) stretch of two lanes sank about 20 centimetres (7.9 in), close to the junction of Telok Blangah Road and Alexandra Road in the evening, resulting in a halting of tunnelling works.

A section of the road above a construction site near Holland Road caved in on the morning of 24 May 2008, creating a massive hole. The hole, directly in front of two private houses along Cornwall Gardens Road, measured 8 by 7 metres and was 3 metres deep. No one was injured, but the road was temporarily closed to traffic.

Line disruptions

On 20 September 2011, a power fault disrupted train services on all 16 stations on the Circle Line. The four hours delay left thousands of commuters stranded during rush-hour. It was reported that leaks and a damaged cable along the Circle Line were the cause of the disruption. The disruption started at about 5.30 am. Train services were gradually restored from 8am and all services were restored just before 10am. Dakota and Mountbatten stations were the last two to resume operations. Investigations were carried out. It was later found that a faulty cable beneath the platform level at Dakota Station caused a power fault on Tuesday morning that affected train services at all 16 stations on the Circle Line. 27,000 passengers were affected by the disruption during the four hours delay, with bus bridging services plying the Circle Line route.

Starting in late August 2016, intermittent signal interference led to a five-day series of train disruptions, which reappeared in November. A team of data scientists explored the data and discovered via a Marey Chart visualization that it was caused by hardware problems sending errant signals from a "rogue" train, PV46.

Stations

The main route goes between Dhoby Ghaut and HarbourFront, with a branch line between Marina Bay and Stadium. Its train frequency is 5 minutes during off-peak, and 2.5 minutes during peak hours, the branch line is being extended to HarbourFront during peak hours and several extended/free travel rides (National Day, New Year's Eve, F1 weekend).

Rolling stock

The rolling stock consists of 40 Alstom Metropolis C830 trains running in three-car formation. They are stabled at Kim Chuan depot, the world's largest underground depot when it opened in 2009. 24 additional Alstom Metropolis & Shanghai Electric C830C trains has started delivery from end July 2014 and began operation from 26 June 2015. Currently all 24 C830Cs are in revenue service.

The automated CBTC system on board relies on "continuous two-way digital communication" between each controlled train and the control centre.

Train control

The Circle Line is equipped with Alstom Urbalis 300 Communications-based train control (CBTC) moving block signalling system on the MASTRIA system with Automatic train control (ATC) under Automatic train operation (ATO) GoA 4 (UTO). The subsystems consist of Automatic train protection (ATP) to govern train speed, Iconis Automatic Train Supervision (ATS) to track and schedule trains and Smartlock Computer-based interlocking (CBI) system that prevents incorrect signal and track points to be set.

Train Data Management System (TDMS) which concentrate and dispatch the rolling stock information with fixed equipment. The IAGO Waveguide communications network has the capability to transmit video and is almost maintenance-free. Base stations are located within the signalling equipment room.

Automatic platform screen doors supplied by Westinghouse provide safety for commuters, offering protection from arriving and departing trains.