I was looking at the real-life operating manuals of some DB locomotives (146 and 185, very interesting as a train fan!), looking at the AFB sections of those manuals it appears a) the AFB automatically applies the direct brake when the train is stopped to prevent rollbacks b) when the power lever is moved forward the AFB will first apply 10-15kn of power c) if the direct brake is applied while rolling, under 60km/h an emergency brake application or traction cut will be triggered after 700m, or 4 seconds over 60 km/h I think the first behaviour is correctly modeled on the 146 but not the 185, and regarding b) I don't think this is modeled at all, which is not ideal as the train will just experience wheel slip in the sim.
It really doesn't, but if I remember correctly from one in-cab video from Siemens Vectron, the direct brake is only to be used when the train is stopped, or going slowly. In regular speeds, all brake operations should be done with the train brake. I guess other german locos follow similar philosophy.
"The auxiliary brake [called direct brake in TSW] is only used when maneuvering and as a holding brake. [so applied to get the train to stay in place after arriving at a stop]"
