R.I. Gen. Laws § 31-14-4

Whenever the state traffic commission shall determine upon the basis of an engineering and traffic investigation that any prima facie speed set forth in § 31-14-2 is greater or less than is reasonable or safe under the conditions found to exist at any intersection or other place or upon any part of a highway, the commission may determine and declare a reasonable and safe prima facie speed limit for that place which shall be effective at all times or during hours of daylight or darkness, or at any other times that may be determined when appropriate signs giving notice of limits are erected at the intersection or other place or part of the highway.