You need to consider very carefully if you really want to drop out of university.
Obviously I don't know you so don't know your exact circumstances, but if you don't have a good reason why you need to (rather than want to) drop out of university, it is not going to be a good trait you are showing your potential employer generally speaking. Questions are bound to be asked at interview stage as to why you wanted to do that, and simply answering "I want this job more" is highly unlikely going to convince your potential employer you will stick with the job.
By all means apply and give it a good go if you want this job really badly, taking onboard what other people have suggested before, but just remember, the railway is a massive industry and you will still have plenty of opportunities in the future even if you miss out on what may seem to be an ideal one for you on this occasion.