The inner shells of the tardis are mapped onto the exterior but that interface is so thin that it fits between atoms so quite literally at the exterior the tardis slips between the layers of atoms in a person's shoes and the ground. At the scale of an atom the electrons are vast distances from the center of an atom so relatively there is actually lots of space to slip through..... and because the interior is so much bigger that tiny space can be a much larger distance such as the distance to the console room because the interior is amplified or larger than normal space. This is identical to walking into the doors steps taken across the doorways extend into the doorway only inside there is no further sides of the police box you cross directly into the larger space.
The Tardis is eventually discovered to be alive. This applies in the sense that it is grown and has the capacity of thought and consciousness. Having said this, it is easy to assume that if 'she' wanted to - A person would remain safe as the actual Tardis came into being and thus encapsulated them within.