The Purple Line is a 23km long mass rapid heavy rail system that will connect Tao Bang Yai in the north-western suburbs of Bangkok in Nonthaburi province with Tao Poon in Bang Sue.

The line will serve the north-western suburbs and the southern area of the city, passing through the centre of the old city on an elevated line.

Currently under construction, the Purple Line is expected to open in 2014. The Mass Rapid Transit Authority of (MRTA) of Thailand has appointed a special purpose vehicle known as the Purple Line Project Consultant (PLPC) to manage and supervise the project completion.

The estimated cost of the project is Baht50bn. MRTA has received a loan of ¥62.4bn from the Japan Bank for International Cooperation, which will be repaid over 25 years.

The Purple Line will have an initial usage of 200,000 passengers a day, which is expected to increase to 290,000 passengers a day by 2022.

Lines and routes of Bangkok’s Purple Line

The Purple Line starts from Khlong Bang Phai depot and runs along the Kanchana Phisek Road to reach Bang Yai terminal.

“The Purple Line is a 23km long mass rapid heavy rail system.”

It will turn left at Rattana Tibet Road and cross over the Rama III bridge over the Chao Phraya River.

It will pass through Nonthaburi Civic Centre and run along the Tiwanon Road and Krung Thep-Nonthaburi Road. It will further pass over Wongsawang intersection flyover and terminate at Tao Poon terminal. The route will be completely elevated and will have 16 stations.

Project details

Construction of the Purple Line is divided into two sections.

The first section lies between the Khlong Bang Pai depot and Phra Nang Klao Bridge. It is 12km long and will have stations at Bang Yai, Sam Yaek Bang Yai, Bang Phlu, Bang Rak Yai, Tha It and Sai Ma.

Construction of 330m long Rama III bridge over the Phraya River forms part of the first section. Physical construction of this section began in November 2009 and is scheduled to be completed by July 2013.

The second section is 11km long and continues from Phra Nanag Klao Bride station to Tao Poon terminal. Construction work on this section commenced in March 2010 and is scheduled to be completed by November 2013.

Rapid transit-Purple Line infrastructure

All the stations except the Tao Poon interchange will have three levels and four entrances at street level.

The Tao Poon interchange station will have four levels with four street level entrances.

The station’s ground floor will house all the mechanical and electrical equipment. The first level will serve as the concourse and will house ticket vending machines, station operation facilities, access gates and retail stores.

Platforms and tracks are situated in the second level. All the stations will have 300m long central platforms which can accommodate a six-car train at the maximum.

To ensure passenger safety and convenience, the platforms will be marked with the train stop points and access doors.

Additional security is provided by half-height platform screen doors between the passengers on the platform and the train.

Tracks will be laid 17m above ground and will be levelled along most of the route. The tracks laid on either side of the platforms will be 14m apart at all stations except at Tao Poon where they will be 18m apart. On the viaduct non-station area tracks will be 4.4m apart.

Park and ride facilities will be available at Sam Yaek Bang Yai, Tha It, Yaek Nonthaburi and at the starting terminal.

The depot will serve as a maintenance, fleet parking and administrative facility. It will house and control the train operating system of the Purple Line.

The Purple Line will be initially serviced by nine trains an hour at headway of 6.45 minutes, which will be later increased to 16 trains an hour at headway of 3.45 minutes with increase in passenger traffic.

Trains will accelerate and deacelerate at a speed of 9m/second. They will travel a distance of 270m to achieve the top speed of 80km/h.

Contracts awarded

Many companies were involved in the consulting stage of the Purple Line project. PLPC was assisted by Asian Engineering Consultants, PCBK International, Chotichinda Mouchel Consultants, MAA Consultants, Moh And Associates, D2 Consult Asia, D2 Consult Ingenieure Zt, Thai Engineering Consultants, Wishakorn Company, DB International and Wisit Engineering Consultants.

“Bangkok’s Purple Line will have an initial usage of 200,000 passengers a day.”

The contract to build the second section was awarded to CKTC joint venture in 2009 for Baht14.3bn. The joint venture is comprised of Ch. Karnchang Public Company and Tokyo Construction.

The second contract was awarded in January 2010 to construct the first section.

Valued at Baht13.1bn, it was awarded to Sino-Thai Engineering and Construction.

The Khlong Bang Phai maintenance building and depot will be constructed by PAR joint venture which comprises of Power Line Engineering, Ascon Constrcution and RNC of Thailand.

Future expansion of Bangkok’s Purple Line

MRTA plans to extend the Purple Line from Tao Poon terminal to Rat Burana. The proposed 17km long extension will have 14 stations. The total length of the Purple Line post extension will be 40km with 30 stations.