(a) No person shall drive a motor vehicle on the site at a speed greater than or in a manner other than is reasonable and prudent for the particular location, given the conditions of traffic, weather, and road surface and having regard to the actual and potential hazards existing.

(b) Except when a special hazard exists that requires lower speed for compliance with paragraph (a) of this section, the speed limit on the site is 25 m.p.h., unless another speed limit has been duly posted, and no person shall drive a motor vehicle on the site in excess of the speed limit.