Silom Line
The Silom Line is an elevated rapid transit line of the BTS Skytrain system in Bangkok, Thailand, extending approximately 14 kilometers from Bang Wa station in the west to National Stadium station in the east while serving 14 stations through key districts including Phasi Charoen, Khlong San, Bangkok Yai, Sathon, Bang Rak, and Pathum Wan.[1] Designated the dark green line, it follows a route along Phetchakasem, Ratchaphruek, and Krung Thon Buri roads before crossing the Chao Phraya River at Saphan Taksin, then proceeding via Sathorn, Silom, and Rama I roads to interconnect with the Sukhumvit Line at Siam station.[1] Operations began on 5 December 1999 with an initial 6.5-kilometer segment from National Stadium to Saphan Taksin comprising four stations, marking a foundational component of Bangkok's modern mass transit infrastructure aimed at alleviating severe road congestion.[2] Subsequent westward extensions progressively added capacity: a 2.2-kilometer link to Wongwian Yai in August 2009, further segments to Talat Phlu in February 2013 and Bang Wa in December 2013 totaling 8.17 kilometers and six stations beyond Saphan Taksin, and the infill Saint Louis station between Chong Nonsi and Surasak in February 2021 to enhance service density in the Sathorn business corridor.[2] Operated by the Bangkok Mass Transit System Public Company Limited under a concession from the Thai government, the line employs automated train control on a viaduct typically 12 meters above road medians, supporting high-frequency service that connects commercial hubs, financial centers, and tourist areas while integrating with ferries at Saphan Taksin and future alignments like the Gold Line.[1][2]History
Planning and construction of the original line
The planning for the original Silom Line formed part of broader efforts to address Bangkok's escalating traffic congestion through elevated mass transit, with initial proposals dating to the early 1990s amid competing bids from entities including the State Railway of Thailand and Bangkok Metropolitan Administration. In September 1991, the Bangkok Mass Transit System Public Company Limited (BTSC) was awarded the concession to develop and operate the initial network, formalized by agreement with the Bangkok Metropolitan Administration on 9 April 1992, with subsequent amendments in 1995 to refine terms including route alignments and financial obligations.[3][4] Construction of the 6.5-kilometer elevated Silom Line, running from National Stadium station to Saphan Taksin station, began in the mid-1990s following site preparations such as piling works, involving the erection of viaducts and stations integrated into the city's dense urban fabric along Silom and Sathorn roads.[5] The project faced significant hurdles, including the 1997 Asian financial crisis, which imposed heavy debt burdens on BTSC—estimated at billions of dollars—and tested the consortium's viability through funding shortfalls and economic contraction, yet proceeded under private financing without direct government bailout for the skytrain component.[6] The line's infrastructure featured standard-gauge tracks on concrete viaducts supported by columns, designed for compatibility with imported rolling stock and automatic train control systems sourced from international suppliers like Siemens and Mitsubishi. Despite initial low ridership projections and operational risks, the segment opened to the public on 5 December 1999, coinciding with the Thai king's birthday celebrations, marking the debut of electric rail transit in Thailand alongside the parallel Sukhumvit Line.[2][7]Initial operations and early extensions
The Silom Line began revenue service on 5 December 1999 as part of the initial phase of the Bangkok Mass Transit System (BTS) Skytrain network, running 6.5 kilometres from National Stadium station in the east to Saphan Taksin station in the southwest.[2][8] This segment included seven stations—National Stadium, Ratchadamri, Sala Daeng, Si Lom, Chong Nonsi, Surasak, and Saphan Taksin—connecting central business and entertainment districts such as Pathum Wan and Sathorn, with an interchange to the Sukhumvit Line at Siam station (though Siam is on the Sukhumvit Line, the lines share platforms there).[8][9] Operations were managed by the Bangkok Mass Transit System Public Company Limited under a 30-year concession, utilizing automated fare collection and air-conditioned trains to alleviate road congestion in Bangkok's densely populated core.[8] Initial daily ridership exceeded expectations, reflecting demand for reliable elevated rail amid the city's traffic challenges, though early years saw financial strains due to construction cost overruns and lower-than-projected passenger volumes influenced by the 1997 Asian financial crisis aftermath.[9] The line's first extension, funded by the Bangkok Metropolitan Administration after delays in central government approval, added 2.2 kilometres westward from Saphan Taksin to Wongwian Yai station, incorporating two new intermediate stations at Krung Thon Buri and Wongwian Yai.[2] Construction commenced on 13 December 2005, with completion postponed from an initial 2007 target due to tendering issues and land acquisition hurdles.[10] Commercial operations on this segment launched on 23 August 2009, extending the total line length to 8.7 kilometres and serving nine stations, thereby improving connectivity to Thonburi-side residential and commercial areas across the Chao Phraya River.[2] This addition increased network capacity and ridership potential, aligning with broader efforts to expand the BTS core system ahead of further westward pushes.[11]Major expansions including Bang Wa
The westward expansion of the Silom Line beyond Saphan Taksin station was planned to alleviate traffic congestion in Bangkok's Thonburi district and connect to emerging residential and commercial areas along the Chao Phraya River's west bank. Construction for the initial phase to Wongwian Yai began on December 13, 2005, funded by the Bangkok Metropolitan Administration after central government approval stalled, with an original target completion within two years but delayed due to tendering issues and land acquisition challenges.[12][13] This phase opened on August 23, 2009, extending 2.7 kilometers and adding two stations—Krung Thon Buri and Wongwian Yai—using elevated viaducts with cast-in-situ concrete methods to minimize disruption in densely populated areas.[2] The extension incorporated Bombardier signaling upgrades to existing rolling stock for improved safety and capacity on the curving alignment crossing the river via a new bridge.[14] Further extension from Wongwian Yai to Bang Wa, spanning 5.3 kilometers and adding three stations (Pho Nimit, Talat Phlu, and Bang Wa), commenced construction around 2010 under a separate Bangkok Metropolitan Administration contract, initially slated for December 2012 but postponed due to utility relocations and structural testing.[13][15] This phase proceeded in three segments during 2013: an initial shuttle service from Wongwian Yai to Pho Nimit in early 2013, followed by integration to Talat Phlu, and full service to Bang Wa commencing December 5, 2013, totaling 4.8 kilometers of new track with four additional platforms.[8][2][16] Bang Wa station, the line's western terminus, features direct interchange facilities with the MRT Blue Line (opened December 2019), though separate ticketing systems persist, enhancing connectivity to suburban routes without unified fares.[16] These expansions increased the Silom Line's total length to approximately 17 kilometers, boosting daily capacity by integrating feeder buses and reducing reliance on road bridges during peak hours.[11] No further operational extensions beyond Bang Wa have occurred as of 2025, though proposals for Taling Chan persist in planning stages.[8]Route and stations
Current route alignment
The Silom Line of the BTS Skytrain system in Bangkok operates as a fully elevated route spanning 14 kilometers with 14 stations, connecting the western suburb of Bang Wa to the central Pathum Wan district. Commencing at Bang Wa station in Phasi Charoen district on the Thonburi side of the Chao Phraya River, the line initially follows an alignment roughly parallel to Phetkasem Road and local thoroughfares through densely populated residential and market areas, passing stations such as Wutthakat, Talat Phlu, Pho Nimit, and Wongwian Yai before curving northward toward the river. It continues via Krung Thon Buri station, serving industrial and commercial zones, and reaches Saphan Taksin station adjacent to the riverfront, where passengers can transfer to Chao Phraya Express Boat services.[1][17] From Saphan Taksin, the alignment crosses the Chao Phraya River on an elevated viaduct, transitioning to the eastern bank and aligning with Sathon Road southward initially before turning northward along key arterial roads in the Sathon and Bang Rak districts. This segment serves high-density business and financial hubs, including stations at Surasak, Chong Nonsi, and Sala Daeng (with interchange to the MRT Blue Line). The route then proceeds along Silom Road, a major commercial corridor, through Si Lom station, before veering slightly east via Ratchadamri Road to Siam station for interchange with the Sukhumvit Line, and finally terminating at National Stadium station near major shopping centers like MBK and Siam Paragon. The entire alignment utilizes standard gauge track with third-rail electrification, designed to bypass ground-level traffic congestion in Bangkok's core.[1][17] The stations, listed from western terminus to eastern terminus, are:| Station Name | District/Area Served |
|---|---|
| Bang Wa | Phasi Charoen |
| Wutthakat | Bangkok Noi |
| Talat Phlu | Bangkok Noi |
| Pho Nimit | Bangkok Noi |
| Wongwian Yai | Khlong San |
| Krung Thon Buri | Khlong San |
| Saphan Taksin | Khlong San (riverfront) |
| Surasak | Sathon |
| Chong Nonsi | Sathon |
| Sala Daeng | Bang Rak/Sathon |
| Si Lom | Bang Rak |
| Ratchadamri | Pathum Wan |
| Siam | Pathum Wan (interchange) |
| National Stadium | Pathum Wan |
Station details and interchanges
The Silom Line operates 14 elevated stations along its approximately 14-kilometer route, connecting central Bangkok's commercial districts with western suburbs.[1] All stations feature platform screen doors, escalators, and elevators for accessibility, with capacities designed for peak-hour crowds exceeding 500 passengers per train.[18] Key interchanges facilitate transfers to other transit modes, enhancing connectivity across Bangkok's network:| Station Code | Station Name (English/Thai) | District | Interchanges |
|---|---|---|---|
| W01 | National Stadium (สนามกีฬาแห่งชาติ) | Pathum Wan | None |
| CEN | Siam (สยาม) | Pathum Wan | BTS Sukhumvit Line[1] |
| S01 | Ratchadamri (ราชดำริ) | Pathum Wan | None |
| S02 | Sala Daeng (ศาลาแดง) | Bang Rak | MRT Blue Line (Silom station)[19] |
| S03 | Chong Nonsi (ช่องนนทรี) | Bang Rak | None |
| S04 | Saint Louis (เซนต์หลุยส์) | Bang Rak | None (opened February 8, 2021)[2] |
| S05 | Surasak (สุรศักดิ์) | Bang Rak | None |
| S06 | Saphan Taksin (สะพานตากสิน) | Bang Kok | Chao Phraya Express Boat piers[1] |
| S07 | Krung Thon Buri (กรุงธนบุรี) | Khlong San | Gold Line (cable-suspended transit to Iconsiam)[19] |
| S08 | Wongwian Yai (วงเวียนใหญ่) | Khlong San | MRT Blue Line (Wongwian Yai station)[20] |
| S09 | Pho Nimit (โพธิ์นิมิตร) | Khlong San | None |
| S10 | Talat Phlu (ตลาดพลู) | Thon Buri | None |
| S11 | Wutthakat (วุฒากร) | Thon Buri | None |
| S12 | Bang Wa (บางหว้า) | Phasi Charoen | MRT Blue Line (Bang Wa station)[21] |
Technical specifications
Infrastructure and track
The Silom Line operates entirely on an elevated guideway constructed from precast segmental concrete viaducts, assembled span-by-span using dry joints and external post-tensioning to minimize disruption in urban areas.[1] These viaducts feature a 9-meter-wide deck elevated approximately 12 meters above road medians, supported by single-column cast concrete piers typically 2 meters wide with spans of 30 to 35 meters.[1] The 3.6-kilometer extension from Saphan Taksin to Bang Wa, completed in 2013, employed cast-in-situ methods for its viaducts, including a bridge spanning the Chao Phraya River.[22] Tracks are electrified using a 750 V DC third rail system, with power delivered via an under-contact rail composed of aluminum backed by a steel contact surface for durability.[2][23] The line incorporates automatic signaling and train control systems, upgraded in the mid-2010s to manage trackside equipment such as points and signals, thereby improving operational capacity during peak hours.[24]Rolling stock
The Silom Line employs 4-car electric multiple unit (EMU) trains from the BTS Skytrain fleet, shared with the Sukhumvit Line but with allocations adjusted for demand on the busier Silom corridor. The primary rolling stock comprises 35 Siemens Modular Metro trains, originally deployed in 1999 at system opening, each configured as A-C-C1-A (two powered end cars with cabs and two trailers) and extended to four cars from initial three-car sets. These trains measure 86.6 meters in length and 3.12 meters in width, accommodating up to 1,490 passengers (168 seated plus standees at 6 per square meter).[25] To support the 2010 extension to Bang Wa and alleviate congestion, 12 CNR (now CRRC) 4-car trains were introduced, featuring a Tc-M-Tc-M configuration with two powered intermediate cars and two trailers, totaling 87.25 meters in length and 3.12 meters in width, with 168 seats and capacity for approximately 1,100 passengers including standees.[26][27] Both types operate on 750 V DC third-rail electrification, incorporate air-conditioning, and support automatic train control for driverless operation in sections, though with onboard supervision.[25][26] By 2017, the combined BTS fleet reached 52 four-car sets, enabling peak headways of 2 minutes on the Silom Line, though maintenance and peak-hour demands occasionally necessitate mixing of Siemens and CNR units.[28] All vehicles feature longitudinal seating, four doors per side per car, and LED/LCD displays for passenger information, optimized for Bangkok's tropical climate with enhanced ventilation systems.[25][26]Operations
Service patterns and headways
The Silom Line operates daily from 6:00 a.m. to midnight, with first trains departing terminal stations around 6:00 a.m. and last trains arriving by midnight.[29][30] All services follow an all-stations pattern, with no express or skip-stop operations in standard scheduling, though signaling constraints limit minimum headways to approximately 3 minutes 45 seconds during peak demand.[31] Headways vary by time of day and weekday versus weekend. During weekday peak hours (roughly 6:00–9:00 a.m. and 4:00–8:00 p.m.), trains run every 3 to 4 minutes to accommodate high ridership in the central business district.[31][32] Off-peak weekday intervals extend to 5–8 minutes, while evenings after 8:00 p.m. and early mornings see headways of 7–10 minutes.[33][34] On weekends and holidays, frequencies are generally consistent with off-peak weekday levels, averaging 6–10 minutes throughout the day to balance capacity with lower demand.[33]| Period | Weekday Headway | Weekend Headway |
|---|---|---|
| Peak (6–9 a.m., 4–8 p.m.) | 3–4 minutes | N/A (off-peak equivalent) |
| Off-peak daytime | 5–8 minutes | 6–10 minutes |
| Evenings/late (after 8 p.m.) | 7–10 minutes | 6–10 minutes |