Quick point ref London and SE. In the South West sector (SWT etc.) from my experience DOO is rare, and that area includes some of the busiest lines. So I'm not sure that the majority of trips ARE DOO, especially if you eliminate LU who seem to have got things running on a reasonably safe basis.
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I'm not a fan of DOO, at least until the supporting technology improves significantly. And even then, being pretty widely read on rail safety, including its history, I'm not sure (as in, it would take a bloody thorough Safety Case to convince me).
Since we DO have DOO on some lines I'm also in favour of improving the supporting tech. For a start there is probably a lot of stuff that can be read over from the MOD Future Infantry Soldier Technology programme on stuff like readability of displays etc. Thats a situation where safety may not be paramount but someone is working to make your day as UNsafe as possible. There are many other ideas that come to mind just idly thinking things through. If we (as in rail staff and passengers together) have to have DOO it is unfair to all of us for the risks not to be mitigated to the greatest extent reasonable.
It strikes me that DOO support systems are a 'poor relation', probably classed as 'Station Systems', officially or otherwise, and thus not accorded the same level of scrutiny and thinking as signalling and the rolling stock. They, in my less informed view, require a good look at, including scrutiny by people outside the rail world who may think in terms of technology that might otherwise not be considered.
For example automated image processing to detect new objects in given areas of a camera view that takes account of weather etc. has been available for free for some time now on inexpensive processing platforms. Whilst I wouldn't see this as a primary tool I could see some utility as a back up alerting device for the Driver - but a lot of thinking and testing would be required before fielding it.
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As to long distance, as a passenger I'm not keen, even if you leave out the safety angle. It may be called 'Customer Service', to me its 'Anarchy Prevention'.
Now First may be saying 'default is to have a TM' at the moment but, with no real pressure to keep things that way, I can see how things will end up. Even the fact that the Driver has to think in terms of two modes, with and without TM support is, to me, a problem.
At the very least there needs to be some sort of formal procedure and criteria to allow Driver Only operation. IMHO at the very least it should require sign off by someone reasonably senior and appear in performance statistics - say count a train run Driver Only as not arriving on time (with no 'beyond out control' get out), as its in a degraded service mode. Or maybe there should be a 'Degraded Service' target, covering Driver Only, catering not provided, excessive toilets locked out etc. <Muses>.