The Alter Rebbe's Rulings on Reshus Harabim
The Alter Rebbe records both the view requiring shishim ribo and the stricter view. His presentation preserves the dispute for practical halacha.
The view requiring shishim ribo
According to the commonly cited lenient definition, width and openness alone do not create a complete Torah public domain without the required passage of shishim ribo.
That view can allow tzuras hapesach in places that would otherwise have the physical form of reshus harabim. It still requires an honest determination of whether the relevant public reaches six hundred thousand.
The stricter view
The Alter Rebbe also records the stricter position, under which a properly formed public street is reshus harabim without making six hundred thousand a necessary condition.
This is not a marginal fact to be omitted from a city-eruv analysis. The responsible posek must decide how the community treats the dispute and what form of enclosure is therefore required.
Practical application in a city
The Rav first establishes the width, openness, alignment, access, and public use of the streets. He then applies the two definitions and the accepted rules of psak.
Only after that decision can the builders know whether ordinary tzuras hapesach is available or whether doors, walls, or another stronger enclosure are needed.