The 900-day construction of three overpass projects over Na Ranong intersection is expected to cause major traffic problems around the area with motorists being advised to avoid the route.

Thanu Tharakhate, of Construction Supervision Division under City Hall's Department of Public Works (DPW), said the Bangkok Metropolitan Administration (BMA) is in the process of publicising details of the project.

"We are also seeking cooperation from motorists to avoid the route while construction is under way," Mr Thanu said.

The construction, which began last Friday, is planned to end in March 2021. (If work actually begins Monday, the 900-day deadline would be April 30, 2021)

The project is planned to enhance the traffic flow on Ratchadaphisek ring road, Mr Thanu said.

Although the ring road is present, traffic jams are not uncommon around the route's intersections.

The overpasses, he said, could be a solution to help address traffic jams at Na Ranong intersection and nearby areas.

The lengthy construction sparked fears of traffic mayhem among motorists.

Meanwhile, Sacred Heart Convent School, located near the intersection, has urged students and their parents to prepare themselves for the inconvenience that could happen over the next couple of years due to the work.

Boonthip Jia, a resident in the area, said she expects traffic mayhem because alternative routes in that area are just small roads and sois.

"The real affected group is cargo trucks that need to take this route to the Klong Toey Port," she said.

"Cargo delivery will be affected by the traffic diversion.

"That affects business, not just commuting time."

Under the project, the existing flyover that connects Queen Sirikit National Convention Centre on Ratchadaphisek Road with Bangkok's popular Penang Market will be torn down and rebuilt with a much longer length and height.

Another new overpass will be a 1.95-kilometre flyover, 15 metres above the ground. It will have four lanes.