Basics…
Anyone who appears in a public place, or can be viewed from a public place can be photographed.
If you, the photographer use that image for personal use, such as adding it to your own photo album, no issues.
If you publish it on the web in say, Photobucket or Flicker, still no issues.
If you sell the image, or publish/use it for personal gain, then the issue of the person in the photo rights come into play.
If they are visible from a public place, and are engaged in their daily work which takes place in plain view to the general public, your pretty much ok.
Look at it from this point…I have a big bay view window in the front of my house.
If I leave the drapes and blinds open and up, and can been seen from the street, anyone can snap my picture…no, they are not invading my privacy.
On the other hand, if I had the drapes drawn, and the photographer stuck his lens in between the drapes to take the shot, then I have a case against the photographer.
The issue of privacy depends on me…if I wish not to be seen, then it is my responsibility to close the drapes, but by leaving them open, I invite people to look in, thus negating and privacy issues.
Same applies to people who work outdoors.
If they wish to not be seen or photographed, it is their responsibility to erect some form of barrier.
If the people or person in the photograph can not be readily or easily identified, then there is no issue there.
If they can be readily and easily identified, or of you zoom in on their face in a close up, then, before you publish the photo for personal gain, you must secure a release for publication statement from the person.
And, if the person is in a group of say, track workers laying rail, and you take the photo from a public street, it is pretty much your image to do with as you see fit, unless one of the group request you to cease photographing them specifically.
That inst