If you're talking street directions Si quis viam quaesit, dicis..., you say, I believe, "Tene viam ad finem (ipsam)" "Keep on this course/road to the (very) end" or "Press straight ahead..." = "In directum niti..." or "I in directum..."
Overlooked this: "Obdura!" will do for "Keep right on to the end", also, without "ad finem" (unless you like the emphasis and want to include "ad finem"), just like "Perfer!"
I'm writing in Latin hoping for correction, and not because I'm confident in how I express myself. Latinè scribo ut ab omnibus corrigar, non quod confidenter me exprimam.