Regardless if it's a train coming or a car/bike coming at you. When you're stopped and preparing to turn or otherwise cross a set of tracks or roadway, it is very difficult to gauge the speed of any oncoming object without really taking time to "study it". With a typical cursory view, it's hard to say with any degree of certainty if you have 6 or 35 or 60 seconds to cross, before the vehicle arrives at your path.
I estimate this train was traveling about 55-60 mph at the time. But when I saw the train coming and ahead about half a mile, and made the u-turn to get ahead of it (drove about 3 miles to next crossing), I thought the train was moving "slowly", and I would have time enough to get set up and perhaps wait a few minutes. I was barely able to get the camera turned on and placed before it rounded the bend, much faster then I thought it would.
So moral of the story is be careful if you see a train and think you can get to the crossing and clear it before it arrives. And if you watch these trains, you may learn (as I did) these trains can actually pick up speed faster then I previously would have assumed.