What about passenger loads or vehicle faults? Or because the driver is getting used to routes and are being thrown straight into higher profile routes whilst getting used to different vehicles, tickets and company operating procedures?

Anyone remember Unit 1 and Unit 2 routes pre 2014? Unit 1 = more experienced drivers and Unit 2 = newer drivers?

Percy Main example from before 2014:

Unit 1: 19, 309, 310, X39
Unit 2: 1, 9, 17, 40/41, 80 and whatever else Percy Main had at the time although I presume the more experienced Unit 2 drivers did the 1?

Would it not be better having more experienced Riverside drivers doing the 21, X10 & X21 on a dedicated rota?