On an old railroad turned bike path I came across a small sign, maybe 8" by

[John]

10" with a black X what is it? X has crossing markings on it..

 

[Cyndi]

It means"Rail Road Crossing".They are still used today.

 

[Derail]

Yup, it alerts the Engineer he's coming up on a road crossing. They're particularly handy at night or in heavy rain or fog.