This Quiet Earth is a good one, though I last watched the movie about 10 years ago. I should give it another viewing, sometime.
In TQE, I don't recall the flood lights and such that you mentioned, but No Blade of Grass and 28 Days later have some similarities to what you described.
Oh, Idaho Transfer, which is stuck in Public Domain Hell (No good legitimate release) is another good one, similar to what you mentioned.
Back to This Quiet Earth. What I recall about the movie, is there is a lot of exploring early on, then the love triangle, then the ending.
Esteban, I'm glad you figured out the title. If you mentioned 80s, I may have figured it out. But now that you've mentioned the title, I think in the next week or so I'll watch it again, it's been long enough.
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