Governing bodies of cities and towns, and county commissioners for unorganized places shall annually, and at other times when advisable, cause to be cut and disposed of, from within the limits of town maintained highways, all trees and bushes that may cause damage or pose a safety hazard to such highways or to the traveling public; provided however that no tree which has a circumference of 15 inches or more at a point 4 feet from the ground shall be removed in the absence of notice to the abutter in the same manner as provided in N.H. Rev. Stat. § 231:145 and N.H. Rev. Stat. § 231:146, except when the delay entailed by such notice would pose an imminent threat to safety or property. Shade and fruit trees that have been set out or marked by the abutting landowners or by the town tree wardens, and young trees standing at a proper distance from the highway and from each other, shall be preserved, as well as banks and hedges of bushes that serve as a protection of the highway, or that add to the beauty of the roadside.