Interesting point about what goes through "regularly" on the train. You might also what to keep an eye out for what goes through irregularly. As an example I used to live in a University town in the middle of the UK that had a main major road run between our dorms and the main campus. Usually nothing very interesting on the road, then ever once in a while a ordinary looking box truck would go past, the giveaway it was worthy of closer inspection were the three police vehicle escort it always had.

One day I was waiting to cross the road when it went past and I noticed the discrete radioactive signs on the side and back. As far as I could ascertain from talking to a few people who should know, it was carrying "medium level" waste on its way to a facility around 200ml to the North East. Apparently it broke its journey at the regional police headquarters, which was only 0.5ml up the road from our dorms!