Mass Transit on Orbital Boulevards
Herbert in comments has been asking me about urban rail on ring roads; Nuremberg has such a road with an active debate about what to do with it. Ring roads are attractive targets for urban rail, since they tend to be wide commercial throughfares. The one in Nuremberg is especially attractive for a tramway, or possibly a medium-capacity metro if one can be built cheaply; this is an artifact of its circumference (18 km) and the city’s size, reminiscent of the Boulevards of the Marshals hosting Paris Tramway Line 3, and the Cologne Gürtel, most of whose length has a tramway as well. Significantly closer-in ring roads, often delineating the medieval or Early Modern walls, are too small for this.
The history of such rings tends to be that they were built based on the extent of the industrial city. Cologne’s was built in the 19th century to connect growing bedroom communities to one another, where they previously only extended along the radial boulevards connecting them to the historic center. The Boulevards of the Marshals delineated the inner end of the Thiers wall from the 1840s; the Périphérique motorway is where the outer end had been. The upshot is that the construction standards are rather modern – for one, the roads are wide. Another upshot is that those roads are often destinations in and of themselves, so that radial rail lines have stops at them; the Métro has stops at every intersection with the Boulevards of the Marshals, generally named after the nearby gate (for example, I lived near Porte de Vincennes, due east along Métro Line 1).
This contrasts with older rings, including one visible on the screenshot above. Those older rings come from premodern city walls, and may not always have enough width to make it easy to build two tram lanes in the center or to do cheap cut-and-cover without disturbing the residences and businesses too much. Even when they do, they’re so close to the center the time savings from a ring at that radius are moderate. Jarrett Walker has long pointed out that people don’t travel in circles, giving the example of the Vienna Ring Road, which has two U-Bahn lines on different sections of it but no continuous ring, as a 5.3 km circle is too small to have viable long relatively linear sections. In Paris, old boulevards closer in than the ring forming Métro Lines 2 and 6 generally have Métro stops but it’s inconsistent, and there’s no coherent circular route to be built.
The modal question – tram or metro – is complicated by special elements of orbital boulevards, which sometimes cancel out, and can work differently in different cities.
In favor of light rail, there’s the issue of speed. Normally, the advantage of subways over tramways is that they’re faster. However, on a circumferential route, the importance of speed is reduced, since people are likely to only travel a relatively short arc, connecting between different radials or from a radial to an off-radial destination. What are more important than speed on such a route are easy transfers and high frequency. Easy transfers could go either way: if the radial routes are underground then it may be possible to construct underground interchanges with short walking, but it isn’t guaranteed, and if there are any difficulties, it’s better to keep it on the surface to shorten the walk time. This has in general been an argument used by pro-tram, anti-subway advocates in Germany, but on routes that rely on multiple transfers, potentially three-legged trips, it is a stronger argument than on a radial line from a suburban housing project to city center.
Frequency is especially delicate. It can be high regardless of mode. Driverless metros can reach 90-second headways or even less, but those are achieved on very busy lines, which need that frequency for throughput more than anything, like Lines 1 and 14 in Paris with their 85-second peak headways. In practice, an orbital tram, especially one in a smaller city than Paris, needs to be prioritizing frequency in order to shorten the trip, not to provide very high throughput, which means that the vehicles could be made smaller than full-size metros, to support frequency in the 3-6 minute range. This could be done at-grade with light rail, or underground with very small-profile metros akin to those used in small Italian cities like Brescia, or even some larger ones like Turin.
In favor of metro, there is the cost issue. The same factors that make speed less important and frequency more important also make it easier to build a metro. If the road is wide enough, which I think the one in Nuremberg is, then cut-and-cover is more feasible, reducing costs. The low required capacity permits intermediate-capacity metros (again, as in Brescia or some smaller French cities), with stations of perhaps 40-50 meters, reducing their construction costs. Nuremberg in particular has had some very low U-Bahn construction costs, so its ability to build an orbital U-Bahn should not be discounted. That said, even at Nuremberg costs – around $100 million/km in 2023 PPPs for U3 extensions – the extra speed provided by such a line, say half an hour to do a full orbit compared with a little less than an hour on a tram, may not be worth it necessarily, whereas such a speedup on a line that passengers may ride for 10 km unlinked would be extremely beneficial.
Pedestrian Observations 
Brussels did build a circular metro line on the early modern city walls, at least for the eastern half of the route. And it’s indeed too close to the centre, there’s little point in transfering between the circle and the inner part of any radial, at least on the closer-in eastern side. It’s faster to take any radial line, even a bus, directly to your destination.
I think the logic was to build it where it was easier instead of where it was most useful. The boulevards are quite wide, and the metro was built simultaneously with road tunnels. Again, since they were tearing open the boulevards anyway to build the road tunnels, it would’ve been relatively cheap to also build the metro. But as a result some important destinations are missed, like Luxembourg, Schuman and Gare du Nord. Instead the metro stops at Porte de Namur and Trône, where a significant part of the walkshed is taken by the dead zone of the royal palace…
This is maybe the origin of the local meme that metros are a car conspiracy. Originally the metro *was* built out together with car infrastructure, and wasn’t as useful as a result.
A possible U-Bahn or Stadtbahn-like connection to Zerzabelshof (often shortened to “Zabo”) has been a perennial debate on the margins of “meeting benefit cost criteria” and was studied in this deceptively named master plan: https://www.nuernberg.de/internet/verkehrsplanung/nahverkehrsentwicklungsplan.html a ring subway unlike a ring tram could deviate from cut and cover (or El) along the ring to better serve the neighborhood with tunneled stations. However, a ring line would not offer the direct city center connection a direct line would.
That said, I don’t think Nuremberg U-Bahn cannot be extended further once U3 is “done” in a couple of years….
There’s also https://www.bahninfo-forum.de/read.php?28,810412 this crayon for a slightly different ring subway, but I feel it would run into problems at Nordwestring….
In a city of Nürnbergs size I think the demand for a 2 transfer ride, that would be the motivation for ring shaped transit would be extremely low.
In a city of that size you should probably just build rail-transit where there is existing demand and density to support it for single-rides. Few people will be happy to make a transfer for within downtown trips, so transfers towards trams should mostly be designed around onwards trip for existing heavy-rail transit nodes.
Nuremberg has the through-station with the most platforms in Europe. And a large share of U-Bahn ridership connects through Hauptbahnhof. And while car traffic within the city is steady or slightly declining, traffic crossing the city limit continues to rise. Nuremberg itself may be “only” ~550k but neighboring Fürth and Erlangen are 100+k each and very much part of the “commute-shed”. If you could keep traffic that has no destination inside the ring outside of it, that would free up capacity….
To me that rather seem to suggest that Nürnberg has a fantastic radial network, with excellent opportunities for central transfers, and exactly those factors will make it very hard to move large passenger numbers to a circle close in distance to the centre.
Nuremberg also has a (mostly) extant ring railway built for freight. It’s partially visible in this map (e.g. next to the “F” of Muggenhof and near where the word “Meistersingerhalle” crosses the road ring, but I think it’s obvious that this ring goes thru some pretty low density places…
What’s your take on Copenhagen’s circular metro?
It’s different, in a bunch of ways:
1. It’s deep-bored and rather undulating, rather than following a circular road with mostly direct subsegments; if you don’t have a suitable ring road and have to bore, then might as well go driverless, and if you need to blast caverns for stations then reducing station size is especially attractive.
2. It’s a circle but it’s not circumferential, in the schema I introduce in the post linked in the lede sentence. Its eastern sections form a north-south radial in city center, just looping back in the west, rather like the Yamanote Line.
3. Conversely, Copenhagen does have circumferential rail, just not as a circle: Ringbanen on the S-Tog provides that service.
A more general observation about Copenhagen that’s applicable to many other cities (including a bunch of American ones, like Washington) is that it’s divided by water, rather than accreting mostly symmetrically around the center like Paris or Nuremberg or Berlin or London. This means that water crossings are a big deal, which reduces the value of a complete circle that crosses the water off-CBD; note that both the M3/M4 ring and Ringbanen are to the west of city center, in the opposite direction from the harbor. Nilo and I were talking about this in the context of Washington – in theory the city could build a circle incorporating parts of the Blue Line, but in practice if there’s money for new Potomac crossings, they should be radial.
What about Line 11 and Line 14 of the Moscow Metro, the offset rings that are farther out than the Line 5 “Circle” but also overlap each other?
No mention of the one in London the, um, um… Circle Line. Apparently they have recently released new Overground maps with each line in a DIFFERENT !! !! color. There’s a circle-ish thing hiding in there.
The Circle line is not a circle, a geographically accurate tube map (such as https://www.whatdotheyknow.com/request/geographically_accurate_map/response/560395/attach/3/London%20Connections%20Map.pdf) shows that it is more of a rectangle, or even a small rectangle attached to a large one. It is also not an orbital or circumferential as Alon is describing: the southern leg runs right through the heart of London (Tower hill, Embankment/Charing Cross, Westminster, etc.) while the parallel northern leg connects most of Landon’s center train terminals (Liverpool St, King’s Cross/St Pancras, Euston, etc.)
Ah it’s not a True True Scotsman.
It’s called the CIRCLE line. The people who actually use it don’t give a flying leap about whether or not pedantic trainspotters think it’s a circle.
Also Paris has line 2 and 6 which together form a circle.
Easy transfers and high frequency are–indeed–keys to success of such lines. Driverless metro has a greater chance of providing that in the long term, both because of lower operating costs and availability of drivers.
I’ve wondered — I know that the cost savings of driverless metro are not 100% of driver costs due to the move to on-train conductors/enforcers and the need for people to manage the driverless system, but what’s the cost savings other places have actually found with their driverless metros? How many years can it take to offset the cost of conversion projects?
There are no on-train conductors anywhere with driverless trains (Paris, Nuremberg, Singapore, Vancouver, at least).
they do have on-platform conductors in Nuremberg, tho.
I think they partially introduced them as a make-work-project for the then-redundant metro drivers…. but they are still a thing in busy times….
Paris, same thing, purely as makework, so all driverless lines run as normal during strikes.
All things considered, it is good to have some employee in each station.
In busy stations it is good to have someone there at all times, and some stations need people for other reasons (if you are serious about getting tourists to use transit you should have someone at the airport under a ask me how to get around this city sign). However it is good to get transit to everyone and if taking full time staff out of less busy stations you can free up enough money to build and run one more station that is far more valuable than the service staff provides in a station. Of course you need someone to clean every station so you can’t completely to away with staff, but most stations don’t need someone there full time.
The general view is that at a minimum you generally need staffed stations or staffed trains (i.e a guard).
Why?
Elevators aren’t staffed, are they?
I could be wrong but I think that SprungUrbanist was referring to roving on-board fare inspection (a la how many German cities do Proof of Payment) not conductors who sit on the trains full time.
Although if a metro system is handling fares this way then the savings from automation is 100% of driver cost since the drivers were not performing fare inspection to begin with. Same for systems that use a fare gate model: they would not add inspectors just eliminate drivers.
I’m referring to fare inspectors, but also how there’s basically always a TfL employee in/around every DLR train, for instance. It’s an argument that comes up in the discourse around security post-covid: having more employees as overseers of the passenger experience in whatever form could be more useful than someone glued to the proverbial cockpit.
London’s DLR trains are driverless but have a “Passenger Service Agent” in charge of the doors, possibly as a make-work.
The agents you see on Paris platforms are not displaced drivers. Metro automatisation is slow (M1 in 2012, M4 in 2023, M13 in 2033?) and drivers are offered positions in other depots. I used to think that platform jobs are make-work. A small book written by a platform employee at Chatelet, Marie France Suzi (Gilets Verts SNCF. Anecdotes d’un regulator de flux du RER D), taught me that the job required college education and a lot of quick thinking on the often unpredictable RER D.
A couple notes about driver costs driving driverless metros:
Driverless makes a massive difference in off-peak and weekend service, because of premium pay and work shifts. 5 minute headways all day become A Thing one can contemplate offering. This is transformative!
Very short headways can mean shorter trains which can mean (radically, if done right) smaller and simpler stations which can mean far more metro constructed for the same cost. Can mean … can mean …
Signalling and safety and train control systems have become so expensive and so embedded that the premium for taking train driver intervention out of the control loop can’t really be a premium any more. Also things that could once be seen an expensive required additional costs for conversion of older metro lines to driverless are increasingly basic infrastructure – I’m thinking platform screen doors as well as ATC
Nuremberg doesn’t have platform screen doors….
Edinburgh trams has one every 7 minutes all day without driverless technology. It isn’t a requirement for high frequency.
Not a requirement, but strongly desired in any country where labor costs are high. Sure you can run high frequency with human operators, but it becomes expensive and so you will also have “bean counters” trying to figure out if they can cut some trains to save money, particularly in a economic downturn when you don’t have money and so something needs to be cut. Driverless trains means there is much less savings from cutting frequency and so they won’t look there.
In countries where labor is cheap you can afford lots of people to do things that could be automated, and it may even be a good things as they get some income. However even those places should be building on the hope they get richer and so eventually will want to switch to full automation.
Switching an existing line to full automation isn’t easy, but still should be on the list for everyone. The safety standards needed to enable full automation are things you want anyway. Humans make mistakes and cannot be debugged near as well as computers. (don’t let someone make those computers too complex though!)
My experience in Vancouver is there were no employees in the various stations. It might be just because I was there on a weekend, or perhaps they were there but hidden from view. The stations were clean so someone was there once in a while, but I never saw them.
Apparently driverless is attractive even in lower income countries. I read yesterday in Metro International, “Alstom Transport India Ltd handed over the first of 52 six-car driverless Metropolis trainsets for the Delhi metro on September 23….”
Anyone know their reasoning?
Most important is for the railway to realise that the marginal cost of running additional service with trains you already have is basically the cost of the staff to run them plus any marginal maintenance subject to track capacity.
Additionally if you need to buy new trains/carriages it is the cost of those new trains/carriages, the maintenance for those trains and carriages and the staff to run them.
That can often be really pretty small.
(And even with automation the staffing cost isn’t zero)
@ bqrail : Everything is relative. In high income countries, transit agencies can ill afford drivers salaries because they are relatively high, in low income countries because metro fares are low. A 6 Egyptian Pounds (0.12 US$) ticket is good for up to 9 stops on Cairo’s metro. Long rides up to 23 stops are 0.24 US$. Cairo’s Metro Line 6 and the monorails will be driverless.
Excellent point.
@dralaindumas, automated trains undoubtedly cost more to buy and maintain so there is a trade-off to be made.
I am sure that is true when driverless (GoA4) is compared with railcars without any automation. But once the norm is GaO2 or higher, with communications-based train control (CBTC), I doubt that the cost of a driverless railcar (GaO4) or its maintenance would be significantly greater. Probably the differences would be in software.
Metro trains have been basically automated for decades. Going all the way and removing the driver’s cabin and climate controls takes out cost, weight and complexity. Paris MP89CC (Conduite Conducteur) trains weigh 144 tons. MP89CA (Conduite Automatique) are 9 tons lighter and the passenger compartment is marginally more spacious.
Taking out the controls altogether also means it cannot be driven manually in an emergency. That is a risk.
That said Egypt and India could use a simpler train design with less technology that would be cheaper to build.
All driverless trains can be driven manually from controls hidden in a cabinet, not only in an emergency but as part of standard procedures at the factory, the depot, and on new subway lines before driverless software is switched on.
Alstom’s factory in Sri City, India, has produced driverless trains for Montreal REM and Sydney metro. Similar Metropolis trains are now being manufactured for Delhi metro at a very competitive price of 1 million Euros/car. What would you remove to make them cheaper? Air conditioning, seats, lights, software lines?
Maybe for a poorer city like Cairo a train like https://en.m.wikipedia.org/wiki/London_Underground_1972_Stock with more mechancial parts and a simpler signalling system would have lower lifetime costs given the cost of Labour etc.
And given the trains are over 50 years old the Bakerloo line does well on reliability – https://content.tfl.gov.uk/service-operated.csv. Much better than the central line with 1990s era trains.
@ Matthew Hutton I suspect a mechanical train would be more expensive. Manufactures have been moving on and so if you try to order one they are likely to say now – they have all the jigs because by contract that have to provide spare parts until 2040 (pick some date in the future), but if they build a new train now they will have to store those jigs until 2065 which costs money.
Some variation is normal and designed for, but some are major changes and expensive to design for. I’m not sure where the limits of this are (ask your train vendor), but eventually in some area they will tell you that you have to take the latest technology like it or not.
I think probably suggesting going full mechanical at this point is a troll and is going too far for the reasons you suggest!
I do agree for developed nations for new lines that they should be automated.
It is also possible that it also makes sense to upgrade existing lines to full automation in developed countries. But TfL have decided it isn’t cost effective and Paris may well be doing it regardless of it being cost effective because of lots of strikes.
I do also agree that CBTC makes sense for complex lines such as the sub surface lines in London and the lines in New York.
I think there is still a question for developing countries whether the right play is to buy basic trains from the manufacturer and to use a simpler signalling system likely with colour light signals.
I may be wrong but I believe Cairo has high costs and that they are going for full automation because of cultural cringe rather than because it makes commercial sense.
Matthew Hutton, just give it up. So much dodging and weaving, changing the subject, what-if-ism, bullshit free-floating “undoubtedly”, all topped by “the simple savages of the developing world should be content with simpler things” — DESPITE THE FACT THAT THEIR URBAN TRANSPORTATION SYSTEMS ARE USED AT LEVELS YOUR ENGLAND BRAIN CAN’T EVEN BEGIN TO COMPREHEND.
You don’t have to reply to ever single damned comment, you know.
Electronics are really cheap these days. So cheap you can hold what would have been a super computer 40 years ago in you hand. So cheap they put less powerful ones into the base of lightbulbs so the lightbulb can connect via wi-fi. And you can use the supercomputer in your hand to change the color. Whirry things and clattering relays likely cost more these days and are less reliable.
Unless the train operators are volunteers, they cost money. Even volunteers cost money because someone would have to manage them.
The whole point of this blog is to say that poorer countries/city need to stop doing cultural cringe towards the west and do early-mid 20th century construction techniques. But that also implies early-mid 20th century health and safety, simpler trains, more focus on lower capital cost even if maintenance time is higher etc.
Now sure probably not hydraulics and you do use electric systems as you say but still.
Hey, Nuremberg is doing some of those techniques as well – parts of the U3 extension are built with cut-and-cover since they’re not under streets but under empty land. Paris is planning on that for the section of the M1 extension through the Bois de Vincennes.
If they are building under “empty” land, shouldn’t they be building even closer to grade in the first place? I don’t necessarily mean strictly at-grade, which would cause problems later (when this open space between city and nucleated suburb/town gets filled in), but a +0.5 embankment or -0.5 trench (daylit, no cover), as a compromise between the construction cost of the rail RoW and the crossing roads.
It’s not empty land. It’s what most people would call a park.
https://en.wikipedia.org/wiki/Bois_de_Vincennes
Yes, but it’s possible to rip parts of it open temporarily, more easily than a street.
Then have the gumption and spine to call it a park. Partly so people like Basil won’t assume it’s potato fields.
I was quoting Alon primarily about the Nuremberg U3. But that aside — why does a line through a park need to be covered, exactly? A daylit trench, whether deep enough to make the trains invisible to people in the park (not immediately next to the trench) or somewhat shallower (possibly even allowing passengers to have a view of the park from the windows) should be cheaper without intruding overmuch on visitors’ enjoyment of the park. E.g. modern track and rolling stock in good condition make fairly little noise to begin with, but even most of that would be either absorbed or radiated at a steep upward angle (where nobody hears it) with very little being radiated outward along the ground.
To be fair people might want to use the park for sports.
Vincennes is not a regular park. It is a protected site. The Chateau de Vincennes was a royal residence before Versailles and would host the French presidency if the Seine flooded central Paris. The RER A curls on the surface around the Bois. Metro Ligne 1 last station is underground next to the Chateau. Trains can continue under the park towards their depot which must be kept in use during any extension works. In the future, two short tunnels will connect the existing Chateau-de-Vincennes station with the TBM-bored twin track tunnel coming from Val de Fontenay. The park will be affected because trees will be cut and fire crew access, ventilation shaft and a 120 square meter transformer station will be visible after the works. This was the basis for public protests against the extension. This issue and the lack of geotechnical inquiry along the chosen route were the reasons why the State refused to grant the Declaration d’Utilite Publique in 2021. Most likely this was just a simple postponement because the visible structures are small and located at the margins of the Bois.
Thank you. You note that there are “premium” costs for weekend/off-peak drivers–how does that relate to the costs of a “peaky” service pattern? I was under the impression that service with strong peaks was MORE costly to operate, not less, due to split shifts and maximum infrastructure/rolling stock, and that service with a peak:off-peak ratio closer to 1 was pretty much always a good thing for costs. It’s been a big argument in DC for why the more consistent headways throughout the day and week are more sensible and how the death of rush hour has liberated the system from costly necessities in many ways.
Driverless operations reduce variable operating costs per train. So what happens with driverless ops is a combination of good off-peak frequency and very high peak frequency – M1 and M14 run every 85 seconds at rush hour, so the peak-to-base ratio is actually on the high side for rapid transit, around 2:1.
Off-peak as in “noon, between the two peaks” and off-peak as in “midnight, after the evening peak” behave differently. At noon, we are speaking of eliminating split shifts. At midnight, of paying a bonus to entice people to take the shift.
(a) Yes, sure, whatever, I never said that, but, sure, whatever, you win.
(b) Yes, sure, whatever, I never said that, but, sure, whatever, you win.
What about the circular subway lines on Beijing’s ring roads?
Only Line 2 overlaps with the ring roads totally. Line 10 does not 100% overlaps with the ring roads, as we say it goes via “3.5th ring” at the north section.
Correction. Line 2 doesn’t overlap with the 2nd Ring at the south.
I was taken by surprise by this statement:
I guess ring roads of the industrial era follow this rule. Ring roads of the car-friendly era follow the opposite rule. Ring roads that I’m used to are usually ring highways or semi-higways and public transport usually puts stops at 200-300 meters of distance of it when it crosses it.
In Barcelona, for example, a ring road line would have connection only with L9 in Parc Logístic, L5 in Can Boixeres, L5 in Vall d’Hebron, L1 in Baró de Viver, and L4 in Barceloneta. But misses connection with all 5 different Rodalies entrances, L10 in Zona Franca, both FGC lines in Cornellà and around Sarrià, tram in Esplugues and La Mina, L3 and L9 in Zona Universitària, L4 in Nou Barris, L9/L10 in Bon Pastor, L2 around Verneda, and L3 in Drassanes.
In Madrid the M-30 also has a good bunch of missed connections. I’m noticing a pattern where being possible to cross the road on foot makes the road an attractor of destinations, or a repellent of destinations?
In car cities the destinations are just off the main ring road highways. The back of your business faces the big highway, but you have a big sign on a large pole next to the highway to ensure everyone driving by knows you are there. The concept is the same even though you are not technically on the ring road.
If I may be pedantic, I’d guess that it’s purely a matter of road design. Compared to what I’ve seen in Canada and Latin America (never been in USA, sorry), Madrid and especially Barcelona are transit and walking cities (but they have ring highways). Even the same ring highway, in the places where it’s built underground, is more of a destination than the places where it just cuts at level.
The old pre car boulevards are inviting for transit and the story of how Diagonal will get a full tram line fighting against a powerful car lobby is sadly too long and epic.
I agree. It’s a major missed point in DC when people, usually people who drive, say “there should be a Metro line that follows the Beltway,” because they confuse the fact that they spend a lot of time using the Beltway to get BETWEEN destinations with the idea that the Beltway directly connects worthy destinations itself. A “Beltway line” would effectively miss almost every important destination in the DC area worth connecting circumferentially.
Just wanted to leave a comment re: Vienna Ring. There used to be two streetcar lines: the 1 and the 2 that made a clockwise and anti-clockwise loop around the ring, respectively. I see that Jarrett Walker notes that of 2009 this is no longer the case. Everyone used to tell visitors to just ride the ring tram for free. I hear that there is a historic tram that makes this route for big money now. Sad.
Do you have any thoughts on the Copenhagen Light rail? While not a circular route in the traditional sense (due to Copenhagen’s geography), it does run on the Ring 3 “ring” road around the west surburbs
Zurich is planning two tram rings to relieve pressure on the center: https://www.stadt-zuerich.ch/site/zukunftsbild2050/de/index.html (in German)
They don’t think a metro would be the right choice: https://vbzonline.ch/u-bahn-ist-in-zuerich-keine-alternative-zu-tram-und-bus/ (again in German)
They talk about additional tram tunnels, hinting towards a Stadtbahn approach. Zurich has significant transit capacity problems in the city center, which should get a lot worse if they start pushing cars out at some point. (Currently hardly any corner is closed to cars.) Therefore, they should move the trams into tunnels in most of the center, but so far their ambition seems much more limited.
Okay, in theory that sounds great and all, but let’s not forget: The ring road might be an artery for motorists. But public transit has it’s arteries elsewhere. The U-Bahn in itself is too big for this city and, well, let’s say, it’s money well spent, but we can’t afford more of it. At least, not a whole ring line. And a ring line with a tram? This would also be a megaproject with questionable use. That’s things naive transit enthusiasts dream about. But in real life in the real world, no one would build transit at such a scale in a city that already has many good tram AND subway lines (for a city this size, this is a unique thing, most cities chose either REAL subway or REAL tram or Stadtbahn (something inbetween). We have both. And we could expand both to ring lines, that would have a practical use:
To make a ring U-Bahn, the most cheap and smart thing for this city would be to use the existing U3 and make this U-shape a circle: You’d begin with digging a junction between Sündersbühl and Gustav-Adolf-Straße. You would need to shut down the southern U3 branch for this, but trains can be rerouted via the U2 branch, creating a denser takt to Röthenbach, or just end at Sündersbühl frankly. Then, using the traditional deep-level boring technique you’d dig a double-track tunnel in a curve to line up with the ring road. There, you could build the first station in cut-and-cover technique or even above ground, as there are no side roads who would be disturbed (Eberhardshof kinda situation). It would be called Westpark. Then, at Jansenbrücke you’d go deeper underground, to go under the existing U1 at Maximilianstraße – ideally you would build a two level underground station like at Hauptbahnhof and give the station a dark orange paint job to make clear: This is an interchange, as this city does this for some reason. Then you could go on with cut-and cover with a third stop at Westfriedhof (change to tram 6). Then, you somehow need to find a way to close the ring with the northern branch of the U3 again. Unfortunately, the Nordwestring station is right underneath the ring road, so you’d have to build a curve again and make a junction into the northern branch between Klinikum Nord and Nordwestring. During that construction, trains could still run and terminate short at Klinikum Nord. In my opinion, the then useless station Nordwestring (doesn’t see much passengers anyways, why did they even build it?) could be abandonned and used as a yard where trains could park, and maybe even replaced by a new one on the then ring line. This would have the added bonus that you wouldn’t need grade-separated crossing between the lines, as no regular traffic is expected to the then old, abandonned Nordwestring station. You could just cross at grade which saves a ton of time and money. The rest of the ring is formed by the U3 as it is.
Tram: The tram is interesting again, as one could form a ring tram by just adding new tracks on a part of the ring road and not the whole thing. So how’d one do it? Starting our ring tram ride at Doku-Zentrum, a station on the ring road, we could of course build tram-tracks along the motorist’s artery of the ring road, but as buses already run there and we don’t want to spend money in this scenario, let’s just use the existing tram tracks and run right through the heart of the Südstadt (like line 8), where many people live. Instead of going to Hauptbahnhof, we go left at the three-quater union at Schweiggerstraße and follow the route of line 10 from Schweiggerstraße to Tiergärtnertor via Steinbühl (S) and Plärrer (U). After Tiergärtnertor (Kaiserburg), our ring tram would turn right into Pirckheimerstraße. The Pirckheimerstraße has no tram line going through it nowadays – but in case of diversions etc. it is still used (or rather was before construction went ahead on another part of the tram network). The next stop would be Rennweg, which is currently refurbished and has an interchange to the U2 to Hauptbahnhof and the Airport. At Rathenauplatz, we’d turn left, following the route of the line 8 again, to Tauroggenstraße, where we meet the ring road again. Here, we would have to build our piece of new track along the ring road, between Tauroggenstraße and Dutzendteich. Here you go, this new ring tram would serve at least as many, if not more people, and we would only have to build new tracks for 1/5th of the whole ring.