In this subtitle:

1. (1) "Exhaust emission system" means a motor vehicle engine modification designed to control or reduce the emission of substances from a motor vehicle or motor vehicle engine, of a model year of 1968 or later, and installed on or incorporated in a motor vehicle or motor vehicle engine in compliance with requirements imposed by the Motor Vehicle Air Pollution Control Act (42 U.S.C. Section 1857 et seq.) or other applicable law.
2. (2) "Metal tire" includes a tire the surface of which in contact with the highway is wholly or partly made of metal or other hard, nonresilient material.

3. (3) "Muffler" means a device that reduces noise using:

   1. (A) a mechanical design, including a series of chambers or baffle plates, to receive exhaust gas from an internal combustion engine; or
   2. (B) turbine wheels to receive exhaust gas from a diesel engine.

4. (4) "Solid tire" includes only a tire that:

   1. (A) is made of rubber or another resilient material; and
   2. (B) does not use compressed air to support its load.

Acts 1995, 74th Leg., ch. 165, Sec. 1, eff. Sept. 1, 1995.