Sorry for the slow response, the run up to Christmas has been quite busy.
how is the brick faced tunnel intended to be distinguished from the existing brick tunnel in terms of function or real life counterpart?
These look great - just want to check though, are they intended to replace existing tunnels or addition? I'd love to add them in early next week before Christmas and release a new binary so if there are any updates let me know.
The Brick faced one really began as an exercise to see if tunnel internals could be done and look good in game. I initially made the internals for the original brick faced tunnel but thought might as well have a go at making a portal as well. It doesn't really serve any alternative function and is loosely based on the generic brick tunnels. Included it here as thought it would add a bit of variety.
the brick arch facings are rather splendid; how have you coded these; are they artificial slope side textures? If so, they would also appear in other contexts than the railway. I produced something like that a while ago (before double heights, so the graphics are no longer usable now), and they could sometimes look a little out of place not in a cutting, although they did look very good in cuttings (and yours look even better).
These are just coded as normal ways. I have been testing ideas for double track with fences/retaining wall to make the layouts a bit more interesting (my menu bar is getting quite busy). I did try coding them as way objects but quickly ran into problems first with stations and then with electrified track.
While I know it would serve no practical purpose, in an ideal world it would be nice to have a "base" object that sits below the track ways (or above in the case of a near side fence) that could be placed perhaps independently of the way its-self (just thinking of, for instance, those odd corners in a cutting that the track doesn't quite fill any more due to a new alignment).
The other issue is, as far as I know Simutrans doesn't support asymmetric way rotations, so you can't rotate your map. Which is fine for me at the moment as I currently have a large map which takes an age to rotate anyway but when I do need to it looks odd.
As to the underground stations, these look good, but I worry a little that there may be some confusion between a station built completely underground and a station on the London Underground network, many of which were not built underground.
The issue I had was that there are very few examples of "underground" stations on the main lines. There are of course other examples of underground station outside of London such as some stations on the Tyne and Wear metro as well as Merseyrail but many of these follow the same basic blueprint of either the subsurface cut and cover/trench type stations or tube station. The closest I could think of was Birmingham New Street, but this was originally built in a trench with a proper canopy roof and only later covered over more fully with other buildings. Unfortunately I feel this is where one could start arguing the symantics about what classes "underground", particularly as the over building of stations with other buildings isn't possible in Simutrans atm.
So to avoid that distinction I turned to London in the first instance.
The stations that I see there look like something from the East London Railway/line (the smaller one) or the Metropolitan Railway/line (the larger one; it is a little like the old Barbican before the overall roof went), which were actually built in cuttings rather than tunnels. Even many stations that appear to be built in tunnels are actually built in cuttings (all the stations on the Circle Line, for example). Certainly, it would make no sense to have an overall roof for a station built in a tunnel.
Incidentally, what is the semi-solid semi-empty overall roof intended to represent?
The station set in the images was based on Paddington Praed Street Station.
Stations actually built in tunnels (as opposed to stations built in cuttings between sections of tunnel) really did not exist until the very late 19th century with the opening of the City & South London Railway, the style of which is represented by the existing "tube" stations. This is suitable for mainline use, too, as exemplified on the Great Northern & City stations. What we could really do with in terms of underground stations is more modern ones (think City Thameslink, the Jubilee Line extension and Crossrail, to give some London examples).
Many of the stations on the west stretch of the original met line (namely Baker street to King's Cross) while built at subsurface level certainly sit within the tunnel rather than an open trench (bar the odd ventilation shaft). During my initial prototyping I had tried to recreate the baker street station, but the results looked odd. Underground versions of the Praed Street Station became a bit of a compromise really, but this is a WIP.
Incidentally the graphics for the tunnel variant are actually slightly different to the trench variant to accommodate the tunnel internals, but again WIP.
I have also prototyped some tube type tunnels, but as with the Praed Street Station this is also a WIP.
Your cutting stations are lovely, and I should hate to see them go to waste, but it is difficult to think of a functional use for them distinct from plain platforms at present (and a plain platform next to your cutting side wall would appear to have the same effect without the somewhat odd look of a cutting side wall in the middle of two platforms not holding anything up).
Which is fair enough, I personally quite like the variety, but that currently comes at the cost of a very busy menu.
Edit: One thing that I notice about the Severn Tunnel type tunnel is that the menu icon for this is in a different style to the menu icons for the other tunnels: the other tunnels have the portal image as their menu icon, whereas this has the tunnel interior. This makes it difficult to find this tunnel amongst other tunnels. Do you think that you could modify the icon image to be consistent with the other icons?
Yep should be easy to swap.