This route is by High Speed Tracks. You can find it here: https://alanthomsonsim.com/downloads/the-railways-of-devon-and-cornwall/
(Fictional). Take a GWR 170 from Exmouth to Exeter with a tight schedule to keep on a busy summer timetable.
Difficulty: Hard
Requirements:
AP class 170 EP (plus TurboTed's GWR reskin)
AP class 158 EP (Cummins)
You can find them here:
https://www.armstrongpowerhouse.com/enhancements/multiple_unit/class_168-170-171_enhancement_pack