A stupid guy I used to know would take a long piece of re-bar, lay it across both rails where the crossing relay for the electric signals started, and run away. He did this at 3-4 a.m. after having too many beers. It was on a rural line with no CTC and no computerized anticipator so the only people who ever came along to remove it were the RCMP after the bell woke up people who lived 25’ from the crossing. He never did get caught as far as I know.
Getting a running start at the low profile obstruction will take the engine right over it, but if the locomotive is stopped, the obstruction placed against the wheel will keep the loco from moving over it. Of course if enough power is applied the wheels may slip and the spinning action could catch the top coin and throw it (rapidly followed by the coin/s below it) like a baseball is thrown from a pitching machine, and then the loco would lurch forward. I wouldn’t want to be to the rear of the wheels if someone were to try this!