A Gadol’s View Confirmed
The Gemara rules that a tzuras hapesach – literally, “appearance of a doorway” – only permits one to carry in a place where doing so is otherwise only rabbinically forbidden. Tzuros hapesach do not permit one to carry in a reshus harabim where carrying is forbidden by Torah law.
The Chazon Ish rules that your average street today is not considered a reshus harabim even if 600,000 people regularly travel on it (Orach Chayim 107:5). This ruling is based on our Gemara, which states that an area surrounded by walls is considered a reshus hayachid even if the walls do not stretch across the entire length of each side. It is sufficient for each wall to run along the majority of its side.
Buildings Here, Buildings There
The Chazon Ish points out that the majority of city streets nowadays are flanked by buildings on both sides. At the end of streets, there is often a dead end or “T,” which closes off the street with a wall, barrier, or building. Although there may be breaks between the buildings aligning the street, this is not relevant. As long as the buildings cover the majority of the street, the street is considered a reshus hayachid.
One possible objection to this ruling is that sometimes a gap of ten amos (about 16 feet) separates buildings, which should strip the street of its reshus hayachid status. The Chazon Ish, however, explains that this rule is only a rabbinic stringency and a tzuras hapesach/eiruv allows one to carry in such a case.
Some Debate, Yet Support
The Chazon Ish himself concedes that this leniency is the subject of debate among earlier poskim. The Beis Ephraim supports the Chazon Ish’s view, but the Mishkanos Yaakov disagrees.
Ancient manuscripts of the Tosefos HaRosh have since been found in which he rules explicitly like the Beis Ephraim and Chazon Ish. No matter how large the gap in the wall, if it encloses the majority of the street, the street is a reshus hayachid according to Torah law if there is a tzuras hapesach (17b s.v. Arba’ah).