Yes, if the railroad catches you out on the main putting down pennies to be flattened by a train they may have you arrested and fined. If you happen to be looking the wrong way for a train when another train comes along you might be injured or killed. Stay away from the tracks whether or not you are in a yard or along a branchline or mainline. It is all tresspassing.
The chances are pretty slim that you will ever find a penny which has been run over by a train at track speeds. They get a little hot and start to stick to a wheel and then they get thrown off into the weeds.
Even though the train weighs 20,000 tons it is the weight on the axle which is the important dimension. So take a 200 ton loco and divide that by 12 for the number of wheels on the loco and that is the number to consider. The result is still enough to squash the penny but no where the 20K tons you were using. Until you develop a better understanding of the forces to deal with stay away and then you should still stay off the property.
Larger coins like quarters and half dollars just get thrown off the track harder and perhaps could injure or maime someone nearby.
It is all fun until someone looses and eye like your mother says.
