I read explanations: ""Since" is a length of time stretching from a point in past time up to the present, while "that" is merely introduces a tensed clause.", "We use 'since' followed by a point in time, not a period". There is the sentence:
- "It was several years since/that I had been travelling that road."
I was told "since" is needed here. But, as far as I understand this sentence: "It was (a some point in time) that (in which) I (already) had been travelling that road." So, according the explanation, I think there must be "that", isn't it? May be there is context where "since/that" are both possible?
Another sentence that was offered to me:
- "It had been several years since I traveled that road."
I understand this sentence this way: "By some point in the past some time had passed after the last time I traveled the road". So in other words: "(By that time) several years had passed since I traveled that road." - right?
Another sentence, that I was told is clumsy but correct:
- "It had been several years since I had been traveling that road."
-is confusing for me, could you please explain the meaning to me?