City Hall opened a partial section of the overpass from Rama III Road to Na Ranong Junction to motorists to relieve traffic congestion which has built up over the past two years.
Bangkok Metropolitan Administration Public Works Department director Taiwut Khankaew said the two-lane overpass from Rama III Road to Sunthorn Kosa Road in Klong Toey district had been open since last week.
"It has worked properly and safely. It will relieve traffic congestion problems at the Na Ranong intersection and Penang Market and traffic conditions will be even better when the whole project is completed in another 12 months," Mr Taiwut said.
He said the City Hall project to build a four-lane overpass over the congested Na Ranong intersection had been under way since late 2018 and is expected to be completed by the end of this year.
The work had removed two flyovers with a plan to replace them with a 1.9-kilometre overpass -- with six traffic lanes altogether -- from Nonsi Wittaya School to Queen Sirikit Natiional Convention Centre on Rama IV.
The overpass has two exit ramps -- one to Na Ranong Junction and another exit ramp to Sunlakakhon Junction.
The contractor also needs to build a new flyover across Chua Phloeng rail crossing.
He said City Hall executives rushed the early opening for this partial exit to reduce traffic impact and air pollution.
The area has recorded dangerously high levels of PM2.5.