The Board of Standards and Appeals may permit accessory group parking facilities with more than 150 spaces in Commercial or Manufacturing Districts, provided either that such facilities have separate entrances and exits on two or more streets or that the following findings are made:

(a)        that such facility, if accessory to a non-residential use, other than a non-profit hospital staff dwelling, has adequate reservoir space at the vehicular entrance to accommodate either 10 automobiles or five percent of the total parking spaces provided by the facility, whichever amount is greater, but in no event shall such reservoir space be required for more than 50 automobiles; and

(b)        that the streets providing access to such use will be adequate to handle the traffic generated thereby.

The Board may prescribe appropriate conditions and safeguards to minimize adverse effects on the character of the surrounding area, including limitations on signs or requirements for locations of entrances or for shielding of floodlights.