The Sukhumvit-Central Road bypass tunnel is now 80 percent complete, with contractors having made up lost time to finish the job by Feb. 1.
Subcontractors currently are working on the interior of the 475-meter-long tunnel, installing lights, security cameras, air-circulation systems, noise barriers and drainage.
While most the exterior work is complete, Napa Construction, the main contractor, has kept detours in place to keep things running smoothly, although signs have been erected to better direct traffic and apologize for the inconvenience.
Workers said the interior work is actually the tricky part as there are many details that take time to get right.
Completion is scheduled for Feb. 1, alleviating fears of delays raised in July when contractors said the project was behind schedule due to rain and flooding, with more delays expected.