I have yet to see someone’s bags being searched in the subways or buses here in New York. Since anyone can refuse to be searched if they want to, this really is not much of a deterrent. If someone does not want their bag checked, they simply can refuse and they will be turned away from the transit point. If someone has a bomb in their backpack, all they have to do is go to another bus stop or subway station.
The searches are random. If someone planned to set off a bomb, they could easily see that police were searching bags and leave.
I really do think this is an example of civil liberties being sacrificed in the name of safety and security when the action being taken does not advance either one bit.