I. Except when directed to proceed by a police officer or traffic control signal, every driver of a vehicle approaching a stop intersection indicated by a stop sign shall stop as required by N.H. Rev. Stat. § 265:31, II, and after having stopped shall yield the right of way to any vehicle which has entered the intersection from another highway or which is approaching so closely on said highway as to constitute an immediate hazard during the time when such driver is moving across or within the intersection.
II. The driver of a vehicle approaching a yield sign shall in obedience to such sign slow down to a speed reasonable for the existing conditions and shall yield the right of way to any vehicle in the intersection or approaching on another highway so closely as to constitute an immediate hazard during the time such driver is moving across or within the intersection. If such a driver is involved in a collision with a vehicle in the intersection after driving past a yield sign without yielding, such collision shall be deemed prima facie evidence of his failure to yield right of way.
III. The driver of a vehicle using an entrance ramp onto a highway shall yield to the vehicles on the highway, regardless of whether there is a yield sign on the entrance ramp.