'this route was' is correct and usable in written English.
You can use it to refer to something that happened in the past: I took a wrong turn and realized too late that this route was a dead end.
Surveillance footage from this route was shown to the jury.
Most of this route was inside Norwegian waters and therefore legally sacrosanct.
Going this route was a strange step for Mr. Hall, who is 73.
Everyone who needed to walk this route was depending upon him to clear the way.
Sportingly, this gave it a summer season to settle into Britain before this route was blocked.
This route was rebuilt with Western aid after the toppling of the Taliban, but has become increasingly dangerous.
But in 1910, this route was in its infancy; the railway route was completed only nine years earlier.
I also believed that this route was likelier to succeed, increasing the probability that the stock has value in the end.
"Unauthorised", "unofficial", "unscheduled", "leaked" - use your own term, but this route was not the normal one.
The ferrites obtained using this route was NixFe3−xO4 (x = 0.5) and MnxFe3−xO4 (x ∼ 0.65).
The hydroxyapatite synthesized using this route was found to be nano-sized (15 50 nm).
