Motorists have been warned of worsening traffic at the Lat Phrao five-way intersection while the extended section of the Green Line electric railway is being built.
The construction of the Green Line extension from Mo Chit to Khu Khot in Pathum Thani is now under way but the focus is on Lat Phrao, where the rail line will traverse the junction at a height of 26 metres.
This part stretches from Mo Chit BTS station to Lat Phrao, which will be built close to Central Lat Phrao department store.
Mass Rapid Transit Authority of Thailand (MRTA) governor Peerayudh Singpatanakul insisted there will be no technical problems in building the elevated rail line at such a height, which is close to the level of a five or six-storey building.
The rail line must be raised that high because the Don Muang Tollway across the intersection is already 20m high.
With the presence of the elevated rail line, four levels of transport construction would exist there, covering Vibhavadi Rangsit Road, the intersection overpass, the Don Muang Tollway and the elevated railway.
A working team overseeing the construction of the Green Line extension will convene this month to iron out plans to manage traffic in the area, Mr Peerayudh said.
The construction will get started when the plans are approved.
Deputy permanent secretary for transport Peraphon Thawornsupacharoen, who also chairs the working team, expressed concerns over the impact of the railway construction on traffic at the intersection.
The Department of Highways, he said, was instructed to work closely with the MRTA to work out plans to deal with traffic before, during and after construction, he said, adding the plans must give details on how to cope with the traffic.
"What is worrying is the plan to deal with traffic before and during construction," Mr Peraphon said.
"After the construction is completed, plans must be drawn up to ward off impacts on motorists," he added.
The governor expressed confidence the extension will be built in accordance with the plan and be finished in 2020.
The construction of the Green Line extension also faces another hurdle at the Ratchayothin intersection on how to deal with the road landscape in the area.
Debates are still ongoing as to whether the Ratchayothin flyover has to be torn down.
An MRTA source said a proposal had been raised that the flyover has to be demolished and replaced by a tunnel to boost traffic flow at the intersection.
However, concerns have flared that the demolition of the overpass could deliver a negative outcome on traffic, and the problem could widen to other areas.
The source, however, noted the overpass is only 9m high and it should not hinder the construction of the Green Line elevated railways, which are planned to be built 16m above ground.
The source said the plan to remove the flyover and replace it with a tunnel was raised by the Office of Transport and Traffic Policy and Planning (OTP), which intends to tackle traffic problems in the long run.
"But this may be difficult to do. Public opinions must be sounded out as there are people who agree and disagree over the matter," the source added.
Mr Peerayudh said work is now under way to minimise footpaths around the Ratchayothin intersection to pave the way for more road surfaces.
He said the work is likely to be completed in October this year.
Afterwards, the flyover will be closed for seven to 10 days as a trial to gauge the impact on the traffic, he said.
The plan for the demolition of the overpass remains in place in accordance with the MRTA board's resolution and City Hall's approval, Mr Peerayudh said.
He did, however, concede that it was unknown as to whether the plan will be revised.