btw - speaking of buses to open rear curtains for the sake of rear view is the most drunken and illegal drugs consumed law ever written. It is nearly impossible to have a view of the rear of the bus from the front from using a smallish mirror and dodging about 50 passengers in the vision.
This is why most buses are either now equipped with cameras or still employ a helper to assist in backing up.
If such laws are even bothered to be written then laws indicating necessary materials and performance standards should be written too. Have you seen the poor plastic sheets that buses use as "windows" in Pakistan?