What is the permissible limit for projection into a public road when no harm is evident?

Primary text

The primary ruling is that constructing any structure over a public road without permission is impermissible because it constitutes building upon the property of others without their authorization, analogous to building a bench or such a structure in a non-cul-de-sac road without the permission of its residents. This contrasts with walking in the road, which is its purpose and causes no lasting harm, or sitting, which is transient and unavoidable. Furthermore, such projections are not entirely harmless; they darken the road, block light, risk falling objects upon passersby, and may cause people to strike their heads as the ground level rises over time. Such structures also impede the passage of beasts of burden carrying loads, thereby blocking the road except for pedestrians. Anything leading to potential harm in the future must be prevented from the outset.