The permittee shall maintain safe crossings for two lanes of vehicle traffic at all street intersections where possible and safe crossings for pedestrians at intervals of not more than three hundred feet. If any excavation is made across any public street, alley or sidewalk, at least one safe crossing shall be maintained when possible for vehicles and pedestrians. If the street is not wide enough to hold the excavated material without using part of the adjacent sidewalk, a passageway at least one-half of the sidewalk width shall be maintained along such sidewalk. (Ord. 106 §10, 1961).