A person commits an offense if he operates a vehicle on any street within the city at a speed greater than 30 miles per hour or on any public alley at a speed greater than 15 miles per hour, unless otherwise provided by this chapter. Any speed in excess of 30 miles per hour on a public street or 15 miles per hour in a public alley, unless otherwise provided by this chapter, shall be prima facie evidence that the speed is not reasonable or prudent and is unlawful. (Ord. 14584)