The following thread if for loading times calculated to be different between riders heroes story run on various versions. Timing for these was done when you hit start game or next track and ended when the blue mission objective disappeared.
PC:
Game start: 5 (seconds) To splash canyon: 5.5 To egg factory: 5.8 To green cave: 5.3 To sand ruins: 5.3 To babylon garden: 8
Gamecube:
Game start: 13.59 To splash canyon: 13.25 To egg factory: 11.62 To green cave: 12 To sand ruins: 10.75 To babylon garden: 17
All load times on consoles are similar. But do not worry, in the future the RTA without load times will be implemented. You also have the option of doing Individual Levels speedrun. I posted the links in this forum in case you are interested. Generally, Riders players have always preferred ILs, for many reasons. But the idea is also to make speedrun of the stories!