"By a certain route" vs. "via a certain route"

Question

Which one is correct:

• by a certain route
• via a certain route

If "by a certain route" is beyond doubt, then when do we use "via"? I always thought that if we go along something (in this case, go along a route), then "via" is used ("via a route").

Answer 1

I see both as semantically correct. Both are used, according to ngrams for by a certain route,via a certain route, the latter less commonly.

My own rationale for not using via and a together is that two ə sounds together sound odd or require extra effort to say. (However, Wiktionary shows the sounds as being different: /ˈviːə/, /ˈvaɪə/ vs. /ɑː/, /a/)

Answer 2

Though both usages are common, using 'by' is more ambiguous. 'by' can mean 'next to' whereas via always describes the traveling itself. So, if the route was 'a highway':

She traveled via a highway She traveled by a highway

In the latter case, her route could have only briefly led her next to the highway.

Answer 3

Beyond doubt it is by a certain route.

via implies through or by way of, which is similar in meaning to route. Therefore, we would not use via and route together.

On the other hand, you could say via a certain point/ place/ other suitable noun, without the use of route.