Why have existing routes not been extended over the life time of TSW. The only two I can find that link are Scotrail Glasgow-Edinburgh and Fife Circle route.
Glasgow-Edinburgh hasn't received an extension. Fife Circle has an extension promised but hopes aren't high. It's more economical to just make a new route for the simple answer. Also, technology and TSW have come a long way since the beginning. The older a route gets, the harder it is to update and extend it. Only because, say a route is released tomorrow for TSW4. It has all the latest features. A route from TSW2 released 2 years ago would need to be updated to include all those new features before the idea of extending the route (if and/or when it makes sense). If you're after a particular older route being updated and/or extended, best to make a suggestion for it. Doesn't guarantee it'll happen though.
Perhaps what I should have said was adding DLC content to continue routes onward. I think the point I was making was it is possible to make a service from Glasgow to Edinburgh. Then even though you have to use another DLC, you can then continue the service through from Edinburgh to Markinch. So it should be possible to continue GWE from Reading to Bristol and beyond, with the next stage starting at Reading onwards for example. The same could also apply to the ECML, or MML.
For Edinburgh-Glasgow specifically, it doesn't make sense to connect it to the Fife Circle route in any way (there are no direct trains from Glasgow via Edinburgh to Markinch plus thenfscy Edinburgh-Glasgow would need updating to accommodating this change). All that's needed for this is the trains for both routes to layer onto the other one (where time periods allow which I think they do in this case). Layering exists for a reason, and that's to put older trains onto the newer routes where appropriate (can't be done the other way due to an old route needing an update first). There's no point in connecting existing routes together, even if they share the same start and/or end point. Layering covers that. If I'm interpreting this right, you mean (where appropriate, for example when two routes share the same non-terminus end point) to have another option when you complete a service, that instead loads up the connecting route so you can continue the journey.
Of the UK routes in the game, favourites for extension are probably TVL (Boulby and/or Bishop Auckland), NTP (York or Liverpool) and Rivet's WCL (on to Plymouth or at least add the Falmouth branch). However DTG have explained the process is far from simple and the amount of developer time means it has to be sold as a new route, resulting in cries of outrage from certain quarters as we just saw with LIRR. Also unlike Run 8 where the developers evolved a system where new sections can be bolted on or continue to run just the section(s) you own, TSW does not have that modularity.
I think that was what I meant. I am new to TSW, so I am still learning. I have heard mention of layering, but have no idea of how to do it. I have added the BR 101 to Centro Line as a one off scenario route. I came to TSW from two truck sim ETS2 and ATS where DLC's join at all points therefor continuing to expand the European and USA maps. There are however marked graphic textural quality differences between the original maps, and the latest DLC's, but SCS does improve the older maps over time.
For layering, you just need the required DLC installed. Take the East Coast Main Line route for example, the Midland Main Line 158 has playable/AI services on the route, but for it to appear, the Midland Main Line route needs to be installed. Also, keep in mind any loco DLC from TSW2 or earlier needs it's home route installed for it to appear (example the Class 20 and Class 31 both also need Tees Valley Line).
I still fail to understand why certain logical branch lines were not included in various UK routes as with making them as very short dlc routes, we will probably never get these branches. This applies to GWE, TVL, BML and WCL in particular but others are likely missing logical parts.
I have the same confusion over a lot of content be it TSC or TSW and not just the DTG routes. I remember the TSC GEML that had two branches, Felixstowe (for freight which makes sense) and Braintree which is absolutely the least interesting branch line in East Anglia. Sudbury to Marks Tey goes through amazing countryside, no OHL needed. Or Harwich, they laid the track but nothing else. Or Southend Victoria, a bustling commuter route. Or the historic Clacton route, the UK's first 25kv electric railway, but no, we get dull old single track, slow speed, underwhelming scenery to Braintree.
