Tetsuji Iida, senior representative of the Japan International Co-operation Agency told LBO that the transport master plan could come up with various recommendations including bus lanes, a Metro system or a combination.
JICA representative Tatsunori Higuchi said the agency will conduct origin and destination studies to monitor traffic patterns in the Greater Colombo region and also interview up to 50,000 commuters and residents as part of developing a transport master plan for the area.
He said plans of Sri Lanka's transport ministry, the urban development and road development agencies would be brought together in the master plan.
The RDA was building a circular expressway around the capital and plans for elevated city roads are also being explored.
Higuchi said the survey data analyzed, economic feasibility determined and proposals of the most appropriate transport modes would be made, which could include mass rail transit (MRT), light rail transit (LRT) or monorail options, he said.
"The Sri Lanka government can decide which transport mode should be introduced to Colombo," Higuchi said.
"Once Sri Lanka government requests JICA, we are ready to finance."
Defence and urban development secretary Gothabaya Rajapaksa told a business forum Wednesday that an MRT running from central Colombo to the Battaramulla area was under consideration.
It would connect bus and rail terminals in Colombo Fort with the Kotte administrative capital where many state agencies are being relocated to, he said.
An MRT system which can go underground in heavily built up areas could be least disruptive but also the most expensive option. An LRT system which is built on elevated tracks could be less expensive.
Costs of an MRT or overhead LRT system involve civil works, the cost of relocating existing housing as well as rolling stock and control systems.
JICA may not be able to fund the entire project on its own.
Mass transit system could cost several billions of dollars to build, depending on their length and needs cities with high population densities and commuters willing to pay relatively higher fares.
Iida said Sri Lankan commuters have got used to paying low rail and bus fares and Sri Lanka's bus route network was one of the most extensive in the region, which went to every place in the city.
Higuchi said with a port city also planned on reclaimed land as well as growth in tourism, transport needs in Metropolitan Colombo is expected to grow.
East Asian mass transit fares start from around two dollars, compared to about 10 cents for a bus in Sri Lanka. Subsidized rail fares are even cheaper.
In Sri Lanka travellers also pay rates comparable or higher rates than East Asian mass transit fares for three wheeler taxis.
In many countries commuters who would otherwise have used cars have shifted to MRTs, helping reduce congestion.
The transport master plan will take into account the entire system or roads and rail, Higuchi said.
A concession was earlier given to a private developer to build an LRT system, but nothing concrete came out of it. Another company has also proposed a rail link connecting the airport to Colombo.
JICA has funded the Delhi Metro. Delhi had a population of 5 million and Bangkok double that. But Sri Lanka's Western province had a population of over 5.0 million Higucchi said.
Jakarta is one of the last remaining large Asian capitals without a metro and it has a dedicated bus lane system - TransJakarta - which has come under fire for taking too much space and moving too little people.
Though MRT systems in some countries are publicly funded, some countries including Thailand and Malaysia private lines have been built with different firms operating different lines.
London's underground steam Metropolitan Railway opened in 1863 was also built by the people themselves. Electric 'tube' trains appeared in 1890. In the 20th century the London underground system was expropriated by rulers.