I understand. Please don't think I'm criticising you. It's just I'm a registered fontaholic, and seeing Arial used anywhere brings on a migraine.
Let me explain: Arial is a font designed for Microsoft as they were cheapskates and didn't want to license Helvetica for their operating systems to use (not completely true, but that's what can be read between the lines of the official history). Arial was designed in 1982, so it ought not to appear on anything that is supposed to date from before then, and to be honest ought not appear on anything since, much like Comic Sans.
Now, the argument could be that even Helvetica is wrong, as the correct typeface for British Rail use is Transport, the same font designed for use on road signs in the early 1960s and still in use there today. Helvetica could be considered close enough to get away with for most generic labelling on rolling stock. Only type dweebs like me might spot the differences between Helvetica and Transport.
Equally, many workshops probably wouldn't use vinyl lettering on things like cranes, and might revert to the time-honoured pot of paint and brush.
Sorry. It must be the heat. I seem to have wandered off into a fontaholic daze.