With the release of the first french line, the LGV Méditerranée, I think it would be a great idea for Dovetail to make more routes in France as there are plenty of interesting lines. Actually, I would love to see RERs (Réseau Express Régional) arrive in TSW, as Paris is my hometown. They're fast suburban trains which go through Paris centre and suburbs. This mean overground and underground, with very interesting variations in the visuals, from tunnels to medium density areas to countrysides. EDIT : I recommend looking at my next detailed post to see the actual viable routes. Here are a few photos of the different RER lines around Paris: RER A (couldn't find a great photo sorry): RER B: RER C: RER D: RER E:
And the map (slightly cut out sorry): I think any of these lines could be added to the game as they're all varied and interesting. (or who knows, Dovetail could add a couple of RER lines or more on the same route - that would be awesome )
The most ideal RER route/corridor for TSW would be one that can be packaged with parallel Transilien/Intercity services, and maybe with the option for a freight add-on, in order to create an interesting array of service layers and really portray the range of French railways like HMA does for Germany. I believe RERs B and D into Gare du Nord or the RER E would offer these opportunities for additional services the most as they run in parallel to the mainlines into the terminals, but I'm not super familiar with the non-commuter Paris rail network. RER E is also much more likely to be available "in full" as well, given that only operates on one side of Paris so it would be easier to build.
After looking more in depth at each RER line, only three of them seem possible as the others are much too long (180 km +) : The RER A, RER B and RER E. The RER A has a length of 109 km. It links Cergy-le-haut / Poissy / Saint-Gemain-en-Laye to Marne-la-Vallée - Chessy / Boissy-Saint-Léger (see map) It's 16 km longer than the LGV, the longest TSW route as from now, but I'm sure Dovetail could make an effort to add those 16 km. It does not have freight but anyway, I think no RERs have freight on their lines. The line has interesting landscape, especially after you come out of Nation. There are two trains, both double deckers, the Mi 09 and Mi 2N. The Mi 09, more common, is the most recent train of the line (2010). Map: Par Chabe01 — Travail personnel, CC BY-SA 4.0, https://commons.wikimedia.org/w/index.php?curid=67068493 Next up, RER B: Saint-Rémy-lès-Chevreuses / Robinson to Aéroport Charles-de-Gaulle 2 TGV / Mitry - Claye (see map) This line, 80 km long, crosses Gare du nord, and offers the possibility to add a second line, the Line K (Gare du Nord to Crépy-en-Valois (see map)), on the route. Line K is more of a regional train, but it follows RER B until its terminus, and further on after that. This regional line is 61 km long, but as most of it follows the RER, it only adds 35 km of route, for a total of about 115 km. This mean there would be two separate lines, RER B and Line K, which adds diversity to the route. Only thing I find a bit annoying about this is that both trains (MI 79 and Z 50000) are single deckers, unlike all the other RER lines in Paris. Maps : Par Chabe01 — Travail personnel, CC BY-SA 4.0, https://commons.wikimedia.org/w/ind Par Chabe01 — Travail personnel, CC BY-SA 4.0, https://commons.wikimedia.org/w/index.php?curid=67146946 Finally, The RER E line, from Paris-Est to Chelles - Gournay / Tournan (see map), is the smallest of Paris, with a size of only 56 km. It only has three stops in Paris centre, and does not have any tunnels. The main advantage is that it rides parallel to the regional Line P, but this one goes further and has a 250 km length. This mean the Line P would need to be stopped before, making it smaller than in real life. A possible cut would be Paris-Est to Crécy-la-Chapelle / Coulommiers (see map). The trains used are the Z 22500 for RER E and Z 50000 shared between RER E and Line P. Maps: Par Chabe01 — Travail personnel, CC BY-SA 4.0, https://commons.wikimedia.org/w/index.php?curid=67072653 Par Chabe01 — Travail personnel, CC BY-SA 4.0, https://commons.wikimedia.org/w/index.php?curid=67121145
The A goes all the way along the center, mostly above ground, so that's probably a very work-intensive line. The E is being made longer, so that does not seem to be a logical priority. Something like the K with the branch of line B to the airport looks really interesting. Only going north from the gare du nord also avoids having to add either the whole bundle from Saint-Denis or the mess that is Châtelet les Halles
Yes, the RER B with line K seems like the best idea. But I don't think the lines should be cut, as they complement each other well without being too long to be built. But for the RER A, I don't really understand why it would be so difficult to modelize as the train goes underground from Nanterre-Préfécture down to Nation, making it, on the contrary, quite easy to build.