If portions of the Master Plan contain proposals for drainage rights-of-way, schools, parks or playgrounds within the proposed subdivision or in its vicinity, or if standards for the allocation of portions of subdivisions for drainage rights-of-way, school sites, park and playground purposes have been adopted, before approving subdivisions the Planning Board may further require that such drainage rights-of-way, school sites, parks or playgrounds be shown in locations and of sizes suitable to their intended uses. The Planning Board shall be permitted to reserve the location and extent of school sites, public parks and playgrounds shown on the Master Plan or any part thereof for a period of one year after the approval of the final plat or within such further time as agreed to by the applying party. Unless during such one-year period or extension thereof the municipality shall have entered into a contract to purchase or shall have instituted condemnation proceedings according to law for said school site, park or play-ground, the subdivider shall not be bound by the proposals for such shown on the Master Plan. This provision shall not apply to the streets and roads or drainage rights-of-way required for final approval of any plat and deemed essential to the public welfare.