The term "grade crossing" when used in this chapter means any point or place where a logging or industrial railroad crosses a highway or a highway crosses such railroad or such railroad crosses any other railroad, at a common grade.

The term "over-crossing" when used in this chapter means any point or place where a highway crosses a railroad by passing above the same.

The term "under-crossing" when used in this chapter means any point or place where a highway crosses a railroad by passing under the same.

The term "over-crossing" or "under-crossing" shall also mean any point or place where one railroad crosses another railroad not at grade.

The term "logging" or "industrial" railroad when used in this chapter shall include every railway owned or operated primarily for the purpose of carrying the property of its owners or operators or a limited class of persons, with all tracks, spurs and sidings used in connection therewith.