Today, the IRS issued proposed regulations relating to the excise taxes imposed on the sale of highway tractors, trailers, trucks, and tires, as well as the use of heavy vehicles on the highway.  The proposed regulations define the term "highway vehicle" as any self-propelled vehicle, or any truck, trailer, or semitrailer, designed to perform a function of transporting a load over public highways.  The proposed regulations reflect legislative changes and court rulings regarding these topics in recent years.