The parking lot shall be provided with attractive walls, guardrails or screening shrubbery, at least along the street side, to limit points of ingress and egress, to prevent encroachment of parked vehicles on any sidewalk, and to improve the general appearance and, where necessary, with a bumper curb parallel with the inside of the wall or guardrail at such distance that the wheels of the motor vehicles in the parking lot are stopped prior to the motor vehicle's contact with the wall or guardrail. (Prior code § 28-1-3)