Feel free to call it what you like. Officially it is designated as an EMU.
A phrase that I've seen used several times (mostly in 'Modern Railways' magazine I think) by supporters of rail electrification is "an electric railway is a better railway, however you define better". The benefits of EMUs are generally considered to include reduced weight and reduced financial costs at most stages of the train's lifecycle (design, build, maintainance and fuel). It seems to me that these benefits are diminished if the unit is carrying one or more diesel engines, as is the case with a bi-mode or an 801. If we are going to say that a class 800 is an electric train then suddenly claims of 'EMUs are lighter and easier to maintain than equivalent DMUs' have to be qualified with 'EMUs,
except class 801s, are lighter and easier to maintain than equivalent DMUs'.
Of course, the diesel engine provides its own, different, set of benefits - but by having it you have already made design and maintainance more complex. A 5-car class 801 is so close to being a bi-mode that I'm struggling to see what advantages it has over a class 800. Presumably the 801 is a bit lighter, but not as light as a straight EMU would be, and the diesel genset on the 801 is used much less often than those on 800s so I guess the maintainance intervals are longer.
So you admit that there is an advantage to the 801 with rescue genset but also speculate that there is no advantage in the vast majority of situations without facts to back that up (London - Peterborough is 76 miles). Indeed north of there 801’s mainly work on sections of the mainline where they only really interact with fellow 80x fleets along with various diesel classes all of which aren’t affected by the OHLE suffering a switch off.
Yes, I admit there is an advantage. Of course self-rescue is a nice-to-have; I guess my question is does it justify the reduced benefits of electric traction? As I said above, I'm not aware of any other rolling stock where this was seen to be worthwhile. Assuming that continues and, as I hope, electrification is rolled out then several of the 'various diesel classes' you mention will eventually be replaced by EMUs.
Extremely useful if it is used to get stranded passengers to an access point such as a station or do you think passengers should just have to sit and wait patiently for hours.
I don't think passengers
should have to wait for hours; I just strongly suspect that in the event of disruption they
will have to wait, regardless of whether the unit has a self-rescue capability or not. I'm just struggling to think of a suituation where self-rescue could actually be used:
- dewirement: there is probably a pantograph tangled in the OHLE meaning that train (and any behind it, which will be a red signals) cannot go anywhere
- national grid power blackout: even if there are only 801s and diesel trains on the line, no pure EMUs or electric locos, there's a good chance the blackout will have taken out the signalling power feeds too
- pantograph damage: switch to the other pantograph
Sure, a self-rescue capability probably would be useful occasionally, but far less often than the ability to keep HVAC, lighting, toilets etc. working while there is no 3rd rail or OHLE power available (which itself will hopefully not be needed very often).
The batteries will run flat long before the fuel runs out. You don’t seem to like the fact that the 801 could potentially get passengers rescued a lot quicker than those sat on an 803 with flattening batteries.
It's not the self-rescue capability that I don't like, but the cost of it - I must admit I am going on gut feelings here but it feels like an 801 has 80%-99% of the drawbacks of a more-capable bi-mode (class 800/802) yet the 801 is useful in fewer suituations.
As for the fuel running out / batteries running flat, which one runs out first is only relevant if one (or both) would run out before the passengers are rescued. If the battery lasts 30 hours* it doesn't really matter if the diesel lasts 50 hours* or 500 hours* since there is something very wrong if it takes more than 3 or 4 hours (on a bad day) to resuce the passengers. I would be interested to know the actual figures (particularly for the batteries) if anyone has them. If 379013 could run for 60 miles in battery mode during the IPEMU trial, surely modern battery tech isn't far off being able to hold a charge for at least 4 hours when it doesn't have to move the train?
* I've no idea how long either would last, I'm just pulling figures out of the air to illustrate the point
To sum up you don’t believe that passengers travelling on an 801 should have the luxury of being able to limp out of a stranding situation because they ‘might’ be thwarted by a 387 which is in the first/final 76 route miles that they work. Interesting.
On an electric railway, which we should be moving towards, that feels like a big 'might' to me. Given the topic title includes 'GWR' you could have an electrified 'MetroWest' with EMUs. It doesn't necessarily have to be a 387 - could be an 803 or IC225, a class 92 on freight. I'm not sure how much of the ECML is 4-tracked - towards the north end you probably have ScotRail EMUs such as 380s or 385 too. Even an 801, depending on the nature of the issue, may be unable to move leaving following units held at danger.