Flickering and shimmering textures on modded tracks

[eitow]

Can somebody tell me how to fix this graphical problem I got on some modded tracks, where textures are flickering and shimmering at the place of dashboard?

The greater intensity of this is most at the start of the track, then it gradually lowers a bit as I drive more on the track. It looks same as the heat shimmering on the highways but at the place of dashboard. Thank you.