This video did not show Dhaka's notorious traffic jam. We need to build underground rail system to reduce traffic congestions in Dhaka.
Traffic jams are not common except in older part of Dhaka and in the Azimpur/Dhanmondi areas.
Many of the next upcoming MRT lines (Lines 1, 2, 4 and 5) will be underground at least partially.
Underground lines will be built only in crowded urbanized densely populated areas, which will be more expensive to build and maintain (even cheap cut and cover situation, not true tunnel boring underground lines) - compared to viaducts (The first one, Line 6, is built on top of viaducts).
Here are more details on Lines 1, 2, 4 and 5.
Note that MRT Line 1 (currently under construction, 2nd line to be built in Dhaka) will be partly viaduct, part underground. Line 4 is still in doubt as non-feasible (Narayanganj route) because there is a dual gauge train line which has been upgraded already for urban commuter rail use. However it still maybe built and extended South.
Further expansion of existing
MRT Line 6 is planned, with the hope of extending it towards
Tongi in
Gazipur metropolitan and
Savar Upazila.
en.wikipedia.org
en.wikipedia.org
en.wikipedia.org
en.wikipedia.org