I. Whenever local authorities in their respective jurisdictions determine on the basis of an engineering or traffic investigation that the prima facie speed permitted under this chapter is greater or less than is reasonable and safe under the conditions found to exist upon a way or part of a way, the local authority may determine and declare a reasonable and safe prima facie limit thereon which:
(a) Decreases the limit at intersections;

Terms Used In New Hampshire Revised Statutes 265:63


(b) Increases the limit within an urban district but not to more than 60 miles per hour;
(c) Decreases the limit outside an urban district but not to less than 25 miles per hour; or
(d) Decreases the limit within any business or urban residence district but not to less than 25 miles per hour.
II. Local authorities in their respective jurisdictions shall determine by an engineering or traffic investigation the proper prima facie speed for all arterial streets and shall declare a reasonable and safe prima facie limit thereon which may be greater or less than the prima facie speed permitted hereunder for an urban district.
II-a. Local authorities shall not be required to hire outside consultants to determine the proper prima facie speed limits as provided in paragraphs I and II if the local community has sufficient staff to conduct the required engineering or traffic investigation.
III. Any altered limit established as hereinabove authorized shall be effective at all times or during hours of darkness or at other times as may be determined when appropriate signs giving notice thereof are erected upon such street or way.
IV. Any alteration of limits on state highways or extensions thereof in a municipality by local authorities shall not be effective until such alteration has been approved by the commissioner of transportation.
V. Notwithstanding the other provisions of this section, local authorities shall modify the speed limits authorized herein so that said speed limits shall not exceed the temporary prima facie speed limits established for the state highway system under N.H. Rev. Stat. § 265:62, II, so long as the same are in effect.