No person shall drive a vehicle on any street or highway within the corporate limits of the city at a speed greater than is reasonable and prudent under the circumstances then existing. Except when a special hazard exists that requires lower speeds in order to operate or drive such vehicle in a reasonable and prudent manner on or entering a highway or street, a speed of thirty (30) miles per hour along the streets and highways within the corporate limits of the city shall be lawful, but any speed in excess of thirty (30) miles per hour shall be prima facie evidence that the speed is not reasonable or prudent and that it is unlawful, except on streets or highways which have a speed limit set by the city or the Texas Department of Highways and Public Transportation which differs from the general speed limit of thirty (30) miles per hour. On any such street or highway, it is lawful to drive a vehicle at the speed which the said highway department or city has posted.
(1998 Code, sec. 10.301)