There's an awful lot of places that are rural locations where DOO-P is in operation on the Chiltern, GWR, Southern, East Anglian and South Eastern lines. Most freight trains are DOO and they can be in the middle of Scotland or the Lake District.
There are many studies that have concluded even in these circumstances DOO-P does not pose a risk, including a couple by RSSB. And we are talking about overall risk, there will be freak occurrences of course. There is no dam or bridge that is 100% safe, no medical operation that is 100% safe. Unfortunately there is not unlimited resources and you cannot prevent all eventualities.
The point is, guards are better off assisting passengers in the event of an accident/incidents and serving their needs rather than running off down the track to apply emergency detonators. Drivers are better off operating doors, if to enable guards to collect tickets, serve and promote rail services get trains away from stations in a timely manner.
It doesn't matter what grade you are, you must report any accident to operations control or the signaller, safety critical or not. In fact, the public are also obliged (morally and in some cases legally) to report serious accidents to the emergency services. In the event of an accident this is what they do. There has been occasions where 999 operators are aware of incidents before the railway authorities are.
The bus point is even more relevant when you consider how reality uncontrolled that environment is. In some ways the railway industry has itself to blame for disputes over the role of the guard. Very few train crew are versed in the signalling regulations and may not be aware of other procedures that come into play during incidents. But it is better to think the railway as 'a system' rather an environment of purely independent vehicles, in that sense they are many inherent advantages over buses (or even aircraft and marine vehicles) in terms of safety, even without a traditional guard on the modern railway.
