Sports training facilities: one parking space for each 250 square feet of gross floor area of principal buildings. Parking requirements for athletic fields shall be determined by the reviewing board at the time of site plan approval on a case-by-case basis, and shall consider whether or not: (1) all athletic fields and principal buildings will be in use at the same time, (2) the time of peak demand for athletic fields and principal buildings will be different, (3) some or all individuals would normally be expected to use both principal buildings and athletic fields during the same site visit, (4) site users will use mass transportation, and (5) other factors in determining parking demand. For purposes of administering this provision only, a covered athletic field shall be considered an athletic field and not a principal building for the purposes of calculating the parking requirement.