If a highway within a city is more than 64 m wide and bisects the entire city, then the city is viewed as divided in two, and the teĥum Shabbat for residents of each of the two sections is calculated separately. This is also the case for a wide-open area such as a park or large garden. If it is more than 64 m wide and bisects the entire city, then the city is viewed as divided in two, and the teĥum Shabbat for each of the two sections is calculated separately.
At first glance, it would seem that the Ayalon Highway divides Tel Aviv into two cities. Nevertheless, since there is an eruv that encompasses all of Tel Aviv and the nearby cities, the eruv unites the different sections. Additionally, if a highway bisects a city but the rectangles drawn around each section overlap, then the overlapping area joins together the sections and we draw a new rectangle around the entire area, as explained above. Additionally, one could argue that since it is intended that all a city’s residents will make use of a highway, park, or large garden, they are considered part of the city and do not actually divide it.
Others disagree, maintaining that these factors – an eruv, usage by all city residents, and overlapping rectangles – cannot join together the two sections formed by a highway or park that bisects a city. The primary position is the lenient one. However, it is proper to be stringent and avoid walking more than twelve mil beyond the highway, since some say that traveling beyond twelve mil is forbidden by Torah law (see section 1 above).
If the road bisecting a city is not straight, the rectangles drawn around each section can overlap, thus uniting the city even if there is no eruv. This opinion was expressed by R. Shalom Noaĥ Segal Weiss in Tikun Eruvin 2:5:39 (p. 211) and n. 156 (pp. 236-237). Maĥazeh Avraham OĤ 70 states that even if the rectangles do not touch each other, as long as the distance between them is less than 64 m, they are considered joined.
Another justification for leniency is that the shi’ur of 64 m – double the size of a city’s outskirts – was based on the standards in talmudic times. However, now that cities are much more sprawling, the entire area that serves the city’s residents should be considered part of the city’s outskirts. This can be derived from the law of a city that is situated next to a stream. If the bank of the stream that is closer to the city has a balcony that is four amot wide, the entire stream is considered part of the city, and the city’s teĥum is measured from the farther bank. This would seem to be the case even when the width of the stream is greater than 64 m. MB 398:46 cites Ritva (Eruvin 61a, s.v. “ve-Ra”Ĥ z”l”) that since “this stream is in front of the whole city and is fit to be used by all the city’s residents, we can consider it an extension of the city even though it is not habitable.” We may also add the possibility raised by MA (398:13) that from the status of the stream we can extrapolate to any place that the city residents use. If so, urban highways are a part of the city even if they are very wide, since their purpose is to be used by the city’s residents. This would also be the case with public parks and gardens. R. Michael Bleicher writes along these lines in Teĥum Shabbat U-medidato, p. 24. (Nevertheless, we see from Rema, cited at the beginning of this note, that the definition of a city is based on physical criteria, not on whether the two sections share a municipality.)
In practice, since the law is rabbinic, we may be lenient, whether based on the rationale that the city has an eruv, or on the rationale that the rectangles drawn around each section overlap. Each rationale is sufficient on its own, and they are even stronger when considered together. Even when distances greater than twelve mil are involved, where some Rishonim maintain that a Torah prohibition applies, we may be lenient based on these rationales. However, if there is no great need, it is proper to defer to the stringent opinion.