We are internally subjective, but our Te filters out this subjectivity before it enters into the real world. I have a lot of thoughts, feelings, and beliefs stemming from my Ni, but I always analyze them with my Te before acting on them, at least in important scenarios.

With your metaphor hap, I disagree about the Ni trying to find the most efficient route, that's Te that would do that. Ni would probably think of the most abstract and interesting route, not the most efficient. When I'm in a serious Ni mood and I'm driving, I take the longest way home, so that I can think about things. When my Te is around, I find the most efficient.