Chabad.org — English translation + Rashi
Torah Temimah (Pesachim 93b): the distant journey is measured from the entrance of the Azarah (or, according to another view, from a fixed distance).
English: What is a distant road? From Modi’im and outward, and the same measure in every direction — the words of Rabbi Akiva. Rabbi Eliezer says: from the threshold of the Azarah and outward.
Definition of distance — the verse’s “distant road” receives a concrete geographic measure in the Oral Law.
Physical distance from the place of the offering is itself a recognized ground for the second opportunity.