Texas Transportation Code - TRANSP § 545.361. Special Speed Limitations

(a) An operator of a moped or a motorcycle equipped with a motor that has an engine piston displacement of 250 cubic centimeters or less may not drive at a speed of more than 35 miles per hour during the time specified by Section 547.302(a) unless the motorcycle or moped is equipped with a headlamp or lamps that reveal a person or vehicle 300 feet ahead.

(b) An operator of a vehicle equipped with solid rubber or cushion tires may not drive at a speed of more than 10 miles per hour.

(c) An operator driving over a bridge or other elevated structure that is a part of a highway may not drive at a speed of more than the maximum speed that can be maintained with safety to the bridge or structure, when signs are posted as provided by this section.

(d) An operator of self-propelled machinery designed or adapted for applying plant food materials or agricultural chemicals and not designed or adapted for the sole purpose of transporting the materials or chemicals may not drive at a speed of more than 30 miles per hour unless the machinery is registered under Chapter 502.

(e) The Texas Transportation Commission, for a state highway, the Texas Turnpike Authority, for any part of a turnpike constructed and maintained by the authority, and a local authority for a highway under the jurisdiction of the local authority, may investigate a bridge or other elevated structure that is a part of a highway.  If after conducting the investigation the commission, turnpike authority, or local authority finds that the structure cannot safely withstand vehicles traveling at a speed otherwise permissible under this subtitle, the commission, turnpike authority, or local authority shall: