The most pressing practical question when dealing with issues of Hotza’ah on Shabbat is whether streets in cities and towns are considered a reshut ha-rabim or karmelit. If streets today are considered a reshut ha-rabim, then it is very difficult to do what is necessary to transform them into a reshut ha-yaĥid. This transformation involves surrounding the entire city with a fence, installing doors in every entranceway, and ensuring that they are all closed at night. Barring this, it would be prohibited to carry in our cities and towns.
In contrast, if streets today are defined as a karmelit (i.e., only rabbinically are they treated as a reshut ha-rabim), then it is relatively easy to transform them into a reshut ha-yaĥid where carrying would be permitted. This transformation involves surrounding the city with a tzurat ha-petaĥ (halakhic doorway), by erecting poles and extending strings between them to form a sort of doorway between every pole (below 29:2-3).
Let us preface our discussion by recalling that the prohibitions of Shabbat are derived from the types of labor performed for the Mishkan. When the Torah commands us to refrain from melakha on Shabbat, it means refraining from Mishkan work, in which the Jews were involved in the desert. If so, then the definition of reshut ha-rabim should also be derived from the Israelites’ desert existence. Since the main thoroughfare in the Israelite camp was sixteen amot wide (7.30 m) in order to enable the passage of the two wagons that transported the different parts of the Mishkan, it follows that only a street equally wide is deemed a reshut ha-rabim. However, Rishonim disagree whether, in order to qualify an area as a reshut ha-rabim, there is also a minimum requirement for the number of people who make use of the street.
Some maintain that any street or marketplace that is open to the public and is sixteen amot wide is considered a reshut ha-rabim by Torah law. It makes no difference how many people pass through each day. According to this opinion, the eruvin that we construct nowadays (namely, the type known as tzurat ha-petaĥ) are ineffective, because our cities have streets wider than sixteen amot. Furthermore, according to this position, as long as a city has streets that are sixteen amot wide, a tzurat ha-petaĥ is not effective for the smaller streets either; the existence of a reshut ha-rabim within an area encompassed by a tzurat ha-petaĥ invalidates it. This is the opinion of Rambam, Rabbeinu Tam, Ramban, Rashba, and many others.
Others maintain that since the camp of the Israelites in the desert consisted of 600,000 men, all of whom needed to walk to the Mishkan in order to help build it and to hear the Torah taught by our teacher Moshe, the Kohanim, and the Levi’im, it follows that a reshut ha-rabim is defined as a road or marketplace that is at least sixteen amot wide, and through which 600,000 people pass daily. If fewer people traverse it daily, it is considered a karmelit. This is the opinion of Behag, Rashi, Smag, Rosh, and many others. Within this position, there is an additional debate. Some maintain that an area still qualifies as a reshut ha-rabim even if it is not used by 600,000 daily, but only frequently or even just occasionally. For in the desert, not all the men traveled on the path to the Mishkan every day. In practice, only in megacities such as New York City and Mexico City are there streets traversed by 600,000 people every day. Even most big cities do not have that many people passing through daily. Thus according to this opinion, most streets are not considered a reshut ha-rabim but rather a karmelit. Therefore, carrying there on Shabbat can be permitted with an eruv of the tzurat ha-petaĥ type. According to this opinion, today the streets considered a reshut ha-rabim by Torah law are mainly intercity highways. Since these roads are meant to serve everybody, and their use is not limited to people of one city alone, they are considered reshut ha-rabim even if fewer than 600,000 people pass through each day.
. BHL 345:7 lists twelve Rishonim who are lenient and twelve who are stringent. According to the simple reading of SA, one should be stringent. Based on this, a number of Aĥaronim write that le-khatĥila Sephardim must be stringent and not rely on an eruv of the tzurat ha-petaĥ type (Yalkut Yosef 345:4; Menuĥat Ahava 3:27:10, 59). In contrast, some Aĥaronim (MA, AHS) argue that R. Yosef Karo did not reach a decision, since SA in multiple places seems to follow the lenient position (303:18; 325:2). In the introduction to the second volume of Or Le-Tziyon 1:1:1-2, R. Ben-Zion Abba Shaul explains that R. Karo is stringent in a case of doubt about a Torah law and lenient in a case of doubt about a rabbinic law. Based on this principle, R. Abba Shaul resolves the apparent contradictions in SA. MA and Taz observe that most poskim tend to be lenient here. Therefore, they continue, one may rely on an eruv of the tzurat ha-petaĥ type to permit carrying in our cities. Many Ashkenazim follow this. Other Aĥaronim write that even though we cannot dissuade those who are lenient, nevertheless it is proper for a one who wishes to act virtuously in the eyes of his Creator to be stringent, since this is a doubt about a Torah law. MB 345:23 states similarly.Regarding the lenient position, some questions have been raised. First, if, indeed, it is necessary to have 600,000 use an area in order for it to be deemed a reshut ha-rabim, how is it possible that this criterion is nowhere mentioned in the Gemara? Second, the Sages decreed that we should not blow the shofar on Rosh Ha-shana if it falls on Shabbat and that we should not shake the lulav on the first day of Sukkot if it falls on Shabbat out of concern that people would carry the shofar or lulav in the public domain (RH 29b). In the time of the Sages, there were no streets with 600,000 people passing through. If a place with fewer than that many people is not considered a reshut ha-rabim, no one could have been carrying in a reshut ha-rabim by Torah law. If this is the case, why did they make their decree? Third, if there is no such thing as a reshut ha-rabim by Torah law today, why did they decree (section 14 below) that women not go out with their jewelry, out of concern that they would carry it?
A possible answer is that the reason that the Sages decreed not to blow the shofar or go out with jewelry on Shabbat is that even according to the lenient position, intercity roads are considered reshut ha-rabim regardless of how many people use them, as explained in BHL 345:7 toward the end of s.v. “she-ein.” In the time of the Sages, traveling on intercity roads was common since the cities were small. People would travel from city to city and from village to city on the same roads. The reason for the difference between intracity roads and intercity ones is that the roads outside a city belong to the entire world. Therefore, even if less than 600,000 people traverse an intercity road daily, it still belongs to the public and is considered a reshut ha-rabim. In contrast, a road within a city or adjacent to it belongs to the city residents and is not a reshut ha-rabim by Torah law. In such a case, only if 600,000 people traverse it daily is it considered a public road rather than belonging to the city’s residents. Based on this, we can understand why the Sages said that if the gates of Jerusalem had not been locked at night, it would have been a reshut ha-rabim (Eruvin 6b), even though presumably fewer than 600,000 people passed through daily. Since Jerusalem served the entire Jewish people, its streets belonged to all the pilgrims, and thus were comparable to intercity roads. Therefore, had the city not been walled, and had the gates not been locked each night, it would have been deemed a reshut ha-rabim. See more in the next note.