Visibility Areas for ‘streets’ is an obnoxious regulation created with public safety (“adequate sight distance”) as the reason. In urban environments, street corners help define community character – just look at wonderful corners scattered all throughout San Francisco!
Enforcing a 25′ x 25′ triangular setback on urban corners (unless you’re willing to argue with the City Engineer over it) does not improve safety. In a city that was developed with small lot width dimensions, this regulation is not only a burden on property owners (having to maintain an open, somewhat public zone on their property) it is a regulation that limits developable building area and increases the cost of construction should you wish to use this area on upper floor levels when many urban zones allow for a zero-foot front & street-side setback.
I am NOT suggesting that Visibility Area regulations at narrower streets, alleys, or driveways be removed, although the entire code section could be revisited.
San Diego Municipal Code