Remember that green little box in front of the Khaleda’s office?
This means of transportation is called a CNG. It is the most common way of getting around if for rickshaw it is too far and you don’t have a car.
A ride of 45-60 minutes will cost about 300 taka (and that is for foreigners!).
The lock is inside and the driver opens/closes it himself.
Here is a little video of one of my rides. I must say that this distance was a very quite one, but still pretty bumpy. If it is in the traffic jam or on the crossroads it is sometimes a bit scary.
Update: CNG stands for compressed natural gas. And! Only in Dhaka they look like cells, in the rest of Bangladesh there are no doors at all!