Except as otherwise provided herein, it shall be unlawful for any person to stop or park any vehicle so as to obstruct a private driveway in any manner, which includes stopping or parking any vehicle within five feet of the outer portion of a curb cut on a private driveway; provided, however, that, in the congested district a vehicle may be parked at the entrance to a driveway providing that ingress and egress to a business conducted on the adjacent premises, only between the period of time after the business served by such driveway has been closed for the day and opening of business on the following day, unless prohibited by signs posted by the City Council.