SRT Dark Red Line
The SRT Dark Red Line is part of the planned SRT Red Line suburban railway system to serve the greater Bangkok Metropolitan Region which includes Bangkok Province and 4 adjoining provinces. It runs on a north–south axis through Bangkok. When fully completed, the line will extend from Thammasat University's Rangsit campus in Pathum Thani Province to Maha Chai in Samut Sakhon Province for a full length of nearly 87 km.

Construction started in 2013 and was originally due to be completed within 3 years. By the end of September 2019, civil works were almost fully complete at 99.56%

In May 2018, the SRT announced that the Dark Red line should finally open in October 2020. Fares will be set at between 14-45 baht. However, more recently the SRT has stated that the new Intercity Terminal at Bang Sue will not open until January 2021 and this is likely to be the date for the line to start operations. 

In July 2016, the Cabinet approved the first section of the southern extension from Bang Sue to Hua Lamphong. However, the 10km 4 station northern extension from Rangsit to Thammasat University will be built first and was expected to be tendered by September 2018. The extension to Thammasat University may now be tendered in the 2nd half of 2019.

The area where the path passes

Route Alignment
Initially, Rangsit to Bang Sue. Eventually, Thammasat University's Rangsit campus in Pathum Thani Province to Maha Chai in Samut Sakhon Province.

History
In February 2009, Prime Minister Abhisit Vejjajiva secured a 24 billion baht (US$685 million) loan from the Japanese Government for the 67 km (42 mi) segment. The first Phase from Bang Sue to Rangsit was approved in 2010 but delayed due to a complicated 2.5 year contractual dispute. 

The 21.6 km, 9 station Rangsit to Bang Sue section finally started construction in May 2013 after new contracts were signed in January 2013. A construction period of 3 years was stated. By the end of 2013, the project was only 3% done & already months behind schedule due to a longer timetable in removing the Hopewell Pillars. In June 2014, the SRT requested an additional 8.14 billion baht to modify the Dark Red line to 4 tracks instead of 3, to accordingly redesign all stations and to provide for the longer platforms for the Bang Sue Terminal to cater for future HSR lines. 8.140 billion baht request is; 4.32 billion baht for Contract 1 (modifications to Bangsue Central to cater for High Speed trains); 3.35 billion Baht for Contract 2 (4th track and stations redesign) and 473 million baht for Contract 3.

It is worth noting that the budget for the 1st Phase of the Dark Red Line project have progressively increased due to numerous delays and further redesign of the project. From an initial 59.89 billion baht in 2007, to 75.55 billion baht in 2009 and to 80.38 billion baht in 2012. The additional requested 8.14 billion baht will increase the current budget to 88.52 billion baht.

Construction Progress
The 26 km, 9 station Bang Sue to Rangsit section finally started construction in May 2013 with a scheduled construction period of 3 years. Construction works were delayed by 2 months due to site access issues for the contractor and delays related to removing slum dwellers residing within the right of way. However, it was hoped that the use of some of the old Hopewell pillars would speed up the initial construction timetable. By the end of 2013, the project was only 3% done & already months behind schedule due to a longer timetable in removing the Hopewell Pillars.

In June 2014, the SRT requested an additional 8.14 billion baht to modify the Dark Red line to 4 tracks instead of 3, to accordingly redesign all stations and to provide for the longer platforms for the Bang Sue Terminal to cater for future HSR lines. 8.140 billion baht request is; 4.32 billion baht for Contract 1 (modifications to Bang Sue to cater for High Speed trains); 3.35 billion Baht for Contract 2 (4th track and stations redesign) and 473 million baht for Contract 3.

As of September 2017, civil works progress was stated to be 88.63%. By the end of September 2019 civil works were almost fully complete at 99.56% and Electrical and Signalling installation was at 45.60%.

New Intercity Terminal at Bang Sue (Contract 1)
Contract 1 of the project is for the construction of a new, 4 level Intercity Terminal to cater for all SRT Intercity Trains, SRT Red Line suburban trains and the yet to be built Airport Rail Link extension. The delayed contract process was finally signed in January 2013. In August 2013, the SRT sought extra funds for the project to be redesigned in order to extend upper level platforms to a 400-600m length in order to accommodate future planned High Speed Lines. (Funding was finally requested in June 2014 - see above section)

In March 2013, the new Intercity Terminal at Bang Sue started construction. Between March and June, excavation works for the foundation of the Terminal were delayed by the unearthing of numerous World War II unexploded bombs which required safe removal by army Explosive Ordnance Teams.
As of July 2014, construction was 10% behind schedule.

The new Bang Sue was originally scheduled to open by end of 2016 but the above-mentioned redesign work and other delays have resulted in an expected 2020 opening date. As of September 2017, construction progress of the station civil works was at 57.50%. By the end of September 2019 civil works were at 86.01% and the new Bang Sue station was expected to finally open in January 2021.

Rolling stock (Contract 3)

The 3rd contract for the Dark Red Line is for electrical and systems (E&S) and procuring EMU rolling stock. An overhead catenary electrical system is specified. As of April 2014, only 2 bidders remained but one of the bidding consortium's was disqualified on due to the fact that one of the consortium members (Maru Beni Corp) had convictions for bribery in an Indonesian bidding process.

This left MHSC Consortium (Mitsubishi and Hitachi and Sumitomo) as the sole bidder qualified for the contract. However, their bid of 28,899 Million Baht was above the SRT median price of 26 billion baht which was set in 2010. The MHSC Consortium argued that their bid reflects 2013 prices after the minimum wage increase of January 2012. Finally, after a 2-year delay in the bidding process, in July 2014 JICA approved the loan for Contract 3. However, the coup of May 2014 delayed finalization leading to further review and negotiations. By mid 2016, negotiations had concluded and Hitachi promised that all rolling stock for the Dark Red line would be delivered by 2020. The contract specifies 25 EMUs consisting of ten 4 car sets and fifteen 6 car sets for 130 cars in total. 

In late September 2019 the first 2 sets of rolling stock were shipped from Japan  and both arrived in Thailand at Laem Chabang port on 12 October 2019 for shipment to Bangkok.

Line segments 
 Bang Sue-Rangsit:  (under construction)
 Rangsit-Thammasat:  (planned for tender in late 2019)
 Bang Sue-Hua Lamphong:  (cabinet approved)
 Hua Lamphong-Bang Bon-Maha Chai:  (planned)

Construction segments 
Construction segments based on M-Map:

There is a future extension that is not included in M-Map, but is included in information brochures.

List of stations