  The concepts of train track was introduced by W. P. Thurston to study the
measured foliations/laminations and the pseudo-Anosov mapping classes on a
surface. In this paper, we translate some concepts of train tracks into the
language of cluster algebras using the Goncharov--Shen's potential function
[GS15]. Through this translation, we prove the sign stability [IK21] of the
general pseudo-Anosov mapping classes.
