Does Dhaka have wide roads to accommodate overhead metro or is it going to be partially underground??
DMRC has done a very good job with Delhi Metro and hopefully will do so in Dhaka.
Delhi Metro is the world's thirteenth largest metro system in terms of length. The metro has an average daily ridership of 2.01 million commuters. Imagine 2 million commuters removed from roads of Dhaka ... it will not only free up roads but also pollution.
Brief history of Delhi Metro:
Physical construction work on the Delhi Metro started on 1 October 1998.
Phase I completed 65.11 km (40.46 mi) of route length, of which 13.01 km (8.08 mi) is underground and 52.10 km (32.37 mi) surface or elevated. First line opened in 2002. The first phase of the project was completed in 2006, on budget and almost three years ahead of schedule, an achievement described by
Business Week as "nothing short of a miracle".
Phase II of the network comprises 128 km (80 mi) of route length and 79 stations, and is fully completed, with the first section opened in June 2008 and the last line opened in August 2011.
The capital cost of Phases I and II has been estimated to be

144.30 billion (US$2.2 billion) at 2004 prices. However, more recent estimates have placed the cost of construction at

2 billion
($31 million) per kilometre.
Phases III (112 km) and IV (108.5 km) are planned to be completed by 2016 and 2021 respectively, with the network spanning 413 km (257 mi). Total daily ridership will increase to 4 million by then.