How will the right answer fit in terms of support and conclusion?

Only the right answer will NOT add support for the conclusion.

Highlight the main conclusion in the passage, if there is one:

it is more dangerous for an individual to drive during the day than during the night.

Journalist: [CONCLUSION]. A recent study found that [SUPPORT].

Map the wording of the answers to the wording of the passage:

(A) …more unsafe than safe vehicles on the road.

That would pretty clearly make it more dangerous during the day, so this one supports the conclusion for sure.

(B) …decreased law enforcement presence…

They expect us to agree that would also clearly it make it more dangerous during the day.

(C) …drive more cautiously during the night…

A good reason why it would be safer at night, which still definitely supports the conclusion.

(D) The number of travelers per vehicle…

This is the only one that doesn’t tell us about night and day. That’s a huge signal that it’s the least relevant answer. And since we don’t know if this info is the same during the day and at night, it can’t support the conclusion.

(E) …drive faster during the day…

No doubt that will make it more dangerous.

(D) is the correct answer.