EMV and Iain says it very well, but to add my own view to that: I've been to several downright hazardous places, and it has always without exception ended up that way because I've earned their trust and proved my reliability by NEVER EVER making demands or bitching about anything, but happily accepting any position I might be given, no matter how bad it might really be. If I end up getting anything I'm happy, if not, cest la vie, I tried :-) But the first thing I always do is clarify that I'll leave in an instant if they find me even in the least bit annoying. I also make perfectly clear how far I am willing to go myself, stating I'm not a daredevil, and some of these places actually square scares me into sometimes ridiculous carefulness and respect.
A dock or train-yard might not seem very threatening, but there are much really heavy machinery, and even the smallest moment of inattention from someone not used to the place might end up badly. The foremen knows this.
When I visit locations there are never no guarantees I'll get any better position after being granted a position, and they might very well say no to even being in the vicinity of the place, but mostly when they'll come to trust me I got very nice things, sometimes even surprising me beyond what I could ever imagine! My greatest pride, that I can actually talk about, was a humongous display-window in a former mall that was up for razing. The foreman didn't wanna let med smash it at first because it would let the dust spread, and quite frankly we both knew what would happen if I cut myself at their location. After being allowed closer and closer as time passed 'till getting some truly amazing positions to the razing, wearing their protective gear, he actually ended up happily smashing it for me and boarding up the gaping hole with plywood! :-)
Mind you, most people actually think these kind'a things are fun, but are not willing to take the consequences if anythings goes wrong and/or anyone would get injured or killed. We must respect that, and neither should we.