Good question, and it's not always clear-cut.
Look for judging or evaluating words.
- Observable facts look like objective statements: there were jeeps and trucks, driven by uniformed drivers.
- Narrator commentary uses subjective judgments or evaluations (usually through adjectives, modal verbs, or metaphor): the war made transport more difficult; people went about as they had always done; the city was tuned to the needs of the soldier.
If you're highlighting, just go with whichever you think is closest. The main thing to watch for is if you do see a subjective thought or feeling word, check whether it's the narrator or a character—and if it's a character, you're too close!