How do you fix the game lagging and stuttering when it's night time? I'd love to play the scenarios but I hate the low fps. I'd love to have my custom scenario all lit up at night, but I have to keep it to daytime hours. Any ideas how to fix?

This is an issue with many games (I have racing sims that literally have half the fps in night driving as during the day, never understood why since there is less being displayed); in RCT it is due mainly to lighting effects, but there is no easy fix; either a better computer or run the game in lower resolution.

You can try playing with display options in the game but by the time you make a noticeable improvement in frame rates you will probably not be happy with the appearance of the game.