How fast do I have to go over the speed limit to get a ticket? Theoretically any speed over the posted speed limit is a violation. CRS 42-4-1101 states that no person shall drive a vehicle on a highway at a speed greater than is reasonable and prudent under the conditions then existing. (2) Except when a special hazard exists that requires a lower speed, the following speeds shall be lawful: (a) Twenty miles per hour on narrow, winding mountain highways or on blind curves; (b) Twenty-five miles per hour in any business district, as defined in section 42-1-102 (11); (c) Thirty miles per hour in any residence district, as defined in section 42-1-102 (80); (d) Forty miles per hour on open mountain highways; (e) Forty-five miles per hour for all vehicles in the business of transporting trash, where higher speeds are posted, when said vehicle is loaded as an exempted vehicle pursuant to section 42-4-507 (3); (f) Fifty-five miles per hour on other open highways which are not on the interstate system, as defined in section 43-2-101 (2), C.R.S., and are not surfaced, four-lane freeways or expressways; (g) Sixty-five miles per hour on surfaced, four-lane highways which are on the interstate system, as defined in section 43-2-101 (2), C.R.S., or are freeways or expressways; (h) Any speed not in excess of a speed limit designated by an official traffic control device. (3) No driver of a vehicle shall fail to decrease the speed of such vehicle from an otherwise lawful speed to a reasonable and prudent speed when a special hazard exists with respect to pedestrians or other traffic or by reason of weather or highway conditions. (4) Except as otherwise provided in paragraph (c) of subsection (8) of this section, any speed in excess of the lawful speeds set forth in subsection (2) of this section shall be prima facie evidence that such speed was not reasonable or prudent under the conditions then existing.