What performance loss though? I have read that perhaps ten to twenty seconds a stop could be saved through DOO. However to me this is bean counting and not practical.
First of all, a guard steps down to physically ensure that their train is placed correctly on the platform (and that they are about to open the right side!) Quite a few guards have told me, that as rookies, the step down saved them from doing something very silly like arming the doors onto an opposite track (I do not want to think further on this, and neither did they) or arming the doors full on an SDO stop. I am informed that drivers are already 'practicing' for DOO or such by turning their shoulders and leaning their heads out of the windows to monitor the platforms etc. This alone will cost five to ten seconds and thus render the point nearly moot! "But they'll have cameras and monitors" I am told. Having seen the grainy scaley monitors some southern services use and the fact that CCTV screens half the time are frankly useless, I can imagine drivers will ignore these and revert to craning their heads out as noted above.
Secondly, it is all very well trying to squeeze an extra ten seconds out of a service here and there, but it is not as if the savings could allow for even more extra services could they? Some lines could not handle any more capacity. I refer to the Birmingham Snow Hill lines and the infamous May 2019 timetable garbage fire. Abellio thought that they could simply ram more services into the spaces between trains at peak time, which in the end caused the Snow Hill lines to near collapse. By that I mean at one point during London Midland days, SH statistics helped propped up the company. After Abellio had broken it, the SH have been a problem child ever since and still are even during covid era 'super sunday' timetables. By throwing in more (and ill planned)services, any time there was a breakdown or disturbance the ripple effect was deeper than pre May 19 scheduling.
COVID has placed everything on ice but behind the scenes, drivers are still being recruited left right and centre, and the 196s are - or were being trial run. I understand these have been cheap, and have caused issues including break down slap bag in the middle of single line branch routes.