Is there only reactive investigations and not proactive steps taken to prevent incident ?
You could argue that the competence management processes that TOC's use with Guards manage this kind of risk as well , Guards will have practical assessments with someone qualified to assess their competence that may pick up any deficiencies with the door operating procedure, there is also unobtrusive monitoring where Guards have unannounced observations carried out of them performing their door procedures . And then there are also briefings which will include discussions around incidents such as this one which do in some cases help to focus minds .
A huge amount of focus in the industry as a whole is now also placed on non technical skills , and there is a growing understanding about how development of those non technical skills can also help to reduce operational incidents such as these .
Does a blind person automatically need assistance or are the capable of being independent ?
Whilst not all visually impaired people will need assistance getting on and off the train , I would suggest that it would still be sensible of a Guard to be aware of anyone on the train that may be in need of additional support for instance if there was an emergency on board or some service disruption that the person may need help dealing with .
Following on from above. What about "process error" or "system error" ? As already mentioned above; if there are technological solutions, surely that then forms part of the mitigation process ?
If my memory serves me correctly I am sure a few years back Northern painted the end passenger doors on 333's a different colour so that they could be better distinguised as being accomodated on the platform at stations that were tight and with curvature which required the conductor to work from a position other than the very rear of the train . A very low-tech solution but I seem to recall it did actually recieve positive feedback form Guards and reduced incidents .Obviously that is easier to do on a route that only sees one type of traction all of the same length
If you operate ASDO with a Balise which essentially measures how much of the train is accomodated and sets a number of doors to be released accordingly then that can also drastically reduce the risk of this kind of incident , if the system is set up correctly and used as intended by Traincrew then the only risks are some error or failure of the interface between on train equipment and the balaise (but even then that is more likely to fail safe so not enable any doors to be released), or some issue with the platform itself like what happened at Moston in 2015 .