Gaon:
“There are basically two shitos on how to determine 600k, according to the Mishkenos Yaakov;
A) its either any road that leads to 600k, no matter the size of the town (as per Ritvah and his opinion in rashi) B) or, all 600k need to traverse through one road etc. (As per shitas Tur and Shulchan Aruch in Rashi) .”
I would just amend it as such: A) The road has the possibility of shishim ribo traversing it (as per Ritva and Rosh). B) The road actually has shishim ribo traversing it (as per Sefer HaTrumah, Semag, Smak, Rokeach, Or Zarua and Maharam MeRotenberg).
It’s of interest to note that the Ritva on Shabbos, which was not printed in the time of the Miskenos Yaakov, uses the term bokim bo as well. Clearly the Ritva when using the terms shyichnsu bo shishim ribo, or derch l’shishim ribo only means to denote that we include in the count, of the shishim ribo, those who do not live in the city, as well.