Great Western Express Xbox One Lag

*please delete if not allowed* I have the original xbox one console and when playing Train Sim World I have noticed that the Great Western Express route is alot more leggy than the Southern Coastway route. I particularly notice the lag on the class 166 but the weird thing is it runs amazingly through parts of the journey and on Southern coastway I do get lag with some long pauses but it happens alot less. Can anyone help please?

 

Sorry ,laggy.