Sentence in question: そこを、対向車線を走る車が、もうスピードですれちがっていく
=> "vehicles, which drive there (=this road) on the opposite lane, pass by with extreme speed."
There are 2 を which both connect the noun to an intransitive verb expressing movement. This use of を is always a bit confusing to me, So I just wanted to ask for confirmation wether I got it right or not. Especially the first を in そこを gives me a headache. そこ clearly refers to the 高速道路 from before, but I'm not so sure wether the first を attaches to すれちがっていく or 走る? I think a relation to 走る would make more sense.
Furthermore, I'm not sure about why in ちがっていく , 行く or 来る should be used at all? AFAIK they usually indicate that something is moving towards or away from the speaker. If the verb is used in this function here, then I wonder why 行く should be preferred over 来る in this context. After all, the object passing by first needs to approach you and then move away from you again.