In my experience, any section of any location with more roadside scenery objects and buildings suffers large performance losses compared to the basics of just trees and shrubs and grass, and more so at night when other light sources are around as you mention.
Be it the villages in Mediterraneo, Monte Carlo, Mexico, Portugal, etc, even the very small block of industrial buildings in Pacifico you snake around in that one section. They all need a lot more optimization.
Turning off the headlights in these sections at night helps, but even then it's still hitting the framerate more than one would expect like there is in the daytime in those areas.
I've already resorted to running most every night stage with my headlights off and brightness cranked up because of this other issue with excessive noise and artifacting on the roads from the headlights interacting with what I assume are the overly strong bump/normal/diffuse maps on the surfaces. Only workaround that skirts that and also helps somewhat with this performance issue at night. It's absolutely silly to have to do, but I don't know if I ever see either of these issues getting addressed in the future so I might as well get used to it. Not a recommendation, just a crummy option.
