I heard that if a trainee spads while the driver trainer is in the cab then the driver trainer is responsible and it goes on their record. I assume if this is true it would put a lot off.
It varies from company to company, some have as 455 driver has said 2 licenses but some just have one. For example if you have a road learner who has 20 years experience in the cab with you and you are a DI and there is an incident then the DI gets the blame, the same goes for anyone driving who is not competent in any of the criteria needed for the rules, route and traction. The DI role is not easy and I personally do not think the enhanced pay is enough to merit the risk, I have had new drivers before questioning me on where to brake for stations, signals and speeds as far as I am concerned if a DI says jump the trainee says how high or is on the cushions for the rest of the day. I have even had one trainee that I refused to work with due to their attitude towards the drivers role.