An overhead bypass above the rail track would have been easier, less inconvenience, and possibly cheaper .......the rail road is a straight 10 kms in length

Yes, without knowing all the details that would have made more sense to me also. The overhead Chonburi expressway is great.

I suspect that these tunnels will just lead to massive congestion at Naklua, though maybe something has been planned about that.

The original plans for the Chonburi expressway were for it to continue & run through Pattaya to Rayong, but the project was stopped, government changed and surprise! they discovered there had been corruption! If they had continued it would have solved so many problems!

The tunnel is a copy of the one that runs through the center of Khon Kaen which works ok, though it took years to build etc!!! must be a good profit margin!

Tunnel will be a disaster. The only thing is does is funnels all that traffic into a more congested area on either side of it. How do I know? The phuket tunnel.