Perennial Calendars!

If you aren't a geek, you can stop reading now, because this is going down a somewhat utopian route. ;-)

Do you still remember the age before smartphones? Then you might also remember those tiny credit-card-sized calendars like the one shown to the right. You can't write almost anything on those and they can't remind you of things. The only purpose they have is to tell which day of each month is which week-day and when public holidays are, because unfortunately, this changes every year, so it's really hard to remember. Maybe you've ever asked yourself why this has to be so complicated: why can't it be the same every year?
If we let aside historical reasons we'll find that the week has seven days, while a year has 365 and roughly a quarter day. (365.242 according to Google.) So even if we'd change the number of days in a week to make it fit, we'd couldn't have every week be just the same length and still fit in a year. (Of course, we could also slightly decrease earth's orbit around the sun, such that we make it around exactly every 364,000 days, because then a year would be just 52 7-day weeks!)

Now, instead of messing with planetary movements, perennial calendars try to simplify the problem rather by introducing better conventions. If we make the concept of "week" a little more flexible, then we can get a calendar which is the same every year and can even get some additional benefits, such as:

• months of more even length
• quarters of more even length 
• months and quarters with a more even number of workdays
• better distribution and simpler to remember public holidays

In the Gregorian calendar, each month has between 28 and 31 days, which makes between 20 and 23 working days which is not only being complicated by a different number of weekends per each month every year, but additionally by public holidays which may or may not fall on weekends. In Germany, for example, depending on the year and the date of Easter, May might have 3 public holidays. If additionally, weekends fall just right, there might only be 19 working days in May. This is especially sad, because most of Germany does not have any public holidays between May or June and the beginning of October, crating a huge holiday-gap after the Spring holiday-boom.

Anyways, here are my two favorite perennial calendars which fix those problems:

Post-Gregorian Calendar: this one's really neat, because it is just a tiny change to our existing calendar which makes a big difference with it's repercussions. This calendar simply makes the first day of every year (1st January) a Sunday by definition. Applying all the normal rules will mean that the last day of the year (31st December) will also be a Sunday. Thus, the major change is simply to have one Sunday be followed by another Sunday. Of course, this would be unacceptable to fundamental Christians, but it would be very practical, since 1st January is a public holiday in most countries anyway, which is practically quite similar to a Sunday. So 31st December would be a normal Sunday (because the day before was a Saturday) and then the 1st January would be a public holiday, where people don't work, so we can make it a Sunday as well. This simple change fixes all the dates of all the non-leap years each to its specific day-of-week. 

As for the leap years, we have to apply one more trick to make them perennial, too, and this trick will be very plain: in non-leap years, 28th February is always a Tuesday and thus 1st March is a Wednesday and we simply keep it that way for the leap-years, too: 29th February becomes a public holiday which you can call an additional Tuesday or a pre-Wednesday or a Middle-of-Week-Sunday or simply "The Leap Day". This might seem quite revolting to conservative people, but it is not much more revolt as having a "double hour" every time we switch back from daylight saving time or having a "date boundary" in the Pacific where on one side it's always one day later than on the other side.

If you think about this more, then the point of the Post-Gregorian calendar is not having an extra day in one or two weeks a year (because all perennial calendars need to have something like that), but the Post-Gregorian's specialty is to put those extra days in places where they least disturb ordinary, conservative life.

Now, after accepting non-weekday Leap Days and the Special "New Year's Day", we can simplify things a bit more and introduce...

The World Calendar. This one's actually been promoted for real and even been discussed at the United Nations. First published by the American Elisabeth Achelis it is one of many proposals that came up after the 18th and 19th centuries when the French Revolutionary calendar was actually made the official calendar of a powerful and modern state. But back to the World Calendar, which is so simple and beautiful that you must love it. It inserts an out-of-week day at the end of every year as well as between the second and third quarters (that is, between 30th June and 1st July) on all the leap years. 

Unlike previous calendar reforms, the World Calendar keeps the names for the twelve months and simply makes the months 31, 30, and 30 days long in each quarter. In recognizing quarter-years as important periods for modern-day business it departs from previous proposals which were more focused on the seasons and agriculture. 

Since each quarter in the World Calendar is the same (and is the same every year) it can be conveniently expressed with the simple table shown here (which I shamelessly copied from Wikipedia). Also note that the months have 22, 22, and 21 work-days in each quarter. So if we had 8 public holidays to spread around the calendar (which is a pretty common number in many countries), we could place them all in the 22-workday-months and obtain a calendar in which every month has exactly 21 working days. (I leave it as an exercise to the reader to find historically significant dates in his or her country which match that pattern.)

There are other Calendars which I also like a lot, especially when they come up with more meaningful names for the months and with more meaningful and less dogmatic public holidays, but I will leave this topic to another post.

To conclude, I only want to mention one type of perennial calendar which I distinctly don't like and that's any calendar which uses leap weeks instead of leap days. Leap weeks were introduced so that the religious seven-day cycle is never broken, hoping that dogmatically religious people will then accept calendar reform. But I think this line of thought will just not work because many conservative people will just not accept any reform and compromising to them will makes matters only more and more and ever more complicated. For example, both calendars described above (as well as almost all other leap-day calendars) keep the same leap-year rules as the Gregorian calendar and will thus start every year on the same day as the corresponding Gregorian year. This is a very useful feature which all the leap-week calendars give up. Besides, to end on a rather subjective note, I just think an entire week popping up between the years is quite unaesthetic and not as nice as having a single public holiday every now and then.

One Year of Meditation -- Accomplishments and the Road Ahead

It is just about one year now since I started to meditate regularly. My introduction and principal guide to the subject has been the Book Search Inside Yourself and it is also the intro book which I would most recommend to anybody curious about the subject.

I started meditation at a time where I suffered from some burnout and a short depression, so my initial goal was just to improve my mood, be more positive and less worked up about things. So during the first couple of months, I meditated with the mantra "calm and content", just repeating these words, as in "I am calm and content", because that's the state of mind I wanted to achieve. If you also want to try, just sit comfortably, close your eyes and thinking "calm" when breathing in, and "content" when breathing out. (If the phrase "I am calm and content" sounds like a lie to you, because your currently aren't, you can simply replace it with "I want to be calm and content". Whatever makes you not being calm might be truly unnerving, but it's the purpose of meditation to let go of such things for the moment of meditating and find the calm within yourself. Usually, when you open your eyes after that exercise, the outer non-calm will also have subsided a bit.)

After the first couple of months I stopped using my mantra and just meditated by concentrating on my breath or by "observing my thoughts" (a technique I learned from a fellow meditator in Berlin). Observing thoughts is very interesting, but it is also an invitation to get carried away by one's thoughts, so it's very important to notice this and go back to more basic forms of meditation where I just concentrate on breath and practice my focus on this.
Although I didn't use the mantra any more, it was still my motto and my main intention for meditation. That's why now, after one year of progress, I decided to focus on a new intention. But before telling you about it, I want to share some of the good outcomes I enjoyed.

First and foremost, meditation really helped me improve my mood. Depression went away, melancholy and lethargy have become far more seldom guests. And I think this worked for the following reasons:

• I am doing more things which I enjoy (and do them even if I have to overcome a little getting-off-my-butt resistance)
• I am doing less things which I don't enjoy
• if I have to do something which I don't enjoy, I am more conscious about my mood management, such as motivating myself (basically convince myself more deeply that I just have to get over it) and minimizing the pain by techniques such as breaking up bigger tasks, enjoy small successes, time-boxing work, and minimizing work to just what is necessary to get the job done. (for the last point, I 

Now, those are all techniques which I had known about before or they are so banal that you might wonder why it needs meditation to figure those things out? (Like, "do what you enjoy," haha, what else would one do?)

The answer to this is that meditation gives me a better self-awareness which means a much better knowledge of what exactly makes me feel good or feel bad. There's a whole science of "Miswanting" now (term coined by psychologist Daniel Gilbert, here's a paper about it, if you like to read science) and I think that meditation really helps to figure that stuff out. For one example, I don't like grocery shopping a lot and I often procrastinated doing it and tried to compensate by combining it with the pleasant activity of a bicycle tour, buying my groceries on the way back home. But as it turned out, this was a bad strategy: my biorhythm seems to prefer spending most of the day inside (reading, doing housework, cooking, and writing blog articles such as this one) and then go biking rather late in the evening, often coming back in the dark. Combining shopping with biking would mean that I can't bike at my preferred time (because shops will be closed on the way back and I don't want to shop on the way out and carry all my groceries through the summer heat for hours) and it also means that I can't go far away from the city, because I have to plan the route such that a store is on the way back. 

In the past, all those complications just demotivated me to go out at all and I didn't really know why. Now I know and I combine grocery shopping with other activities, such as grabbing a quick lunch outside. And for biking, I now more often invest some time on a train to go a little farther away from the city. Or I head directly towards the shortest and nicest way out of the city.

To conclude, I think that I am now somewhat more calm and definitely more positive and happy! Choosing my next meditation goal was very easy, because there are two other basic skills or attributes mentioned in the book, which seemed to be particularly lacking in my life. Therefore I decided to work during the next six months to improve my concentration and my resilience. But more on that in another post.

(By the way, I am planning this for six months because that's my preferred mid-term planning horizon ever since I read Tim Ferris' "Four-hour work-week". It's not that profound a book, but has some interesting tips nevertheless. So I try to plan almost nothing ahead of those six months, because I think when you do really adventurous and great things, they will change yourself so much that after six months, your priorities will be quite unpredictable from now. I find it quite funny to think that "agile software development" teaches something very similar: after each iteration delivered to the customers, you'll get new problems and desires which you couldn't have planned for at the beginning, that's why you should aim for short delivery cycles. But anyway, that's why just six months!)

how to set audacious goals and make everybody win

Actually I gave the solution away in the title already, but here's a little pre-story: Tim Ferris once stated (either in his book 4HWW or on his blog) that we should go ahead and choose very high goals, because nobody else dares to aim that high and we'll therefore have less competition. His canonical example is horny men trying to hook up with pretty girls, but not daring to approach the most stunning beauties of all. Therefore, he claims, anybody who seriously and competently hits on that person, will have higher than average success. But I think this is quite wrong, since the very definition of attractive appearance in those circles is that it attracts a lot of people, including unfortunately for everybody in the game some delusional losers who don't even know how to talk to other people and even less so when they are horny. As a consequence, the most desirable women can sometimes by quite annoyed by those people and therefore much more reserved and selective, which in turn makes them less fun to talk to. Additionally, since attraction is by definition hard to ignore, there are probably a few actually nice and very sociable men who set their eyes on the princesses of this world, so no matter how much competition there is, it will be much tougher.

But let's talk any further about the wrong approach to life, when the right one is so close. Like Tim Ferris, I believe that most people can actually aim much higher than they do and achieve their goals (without totally exhaust themselves in the process). The key is, in fact, very simple: don't choose competitive goals! Most people simply fall victim to the imitation bias and want things that other want, too, and if this thing happens to be a limited resource, then there will of course be competition and it will take much effort to win and with every winner, there will be losers, but losers might try again later, so more effort will be spent on all sides. A lot of books have been written about this, how to compete, how to convince, how to sell, and it will never be enough, since the competition obviously reads the same books, too.
On the other hand, if you and other people want something that you all can have and losslessly share, without anybody else losing it (or something else of similar value), then you'll probably get it pretty easily if you do it right and much importantly, it will get easier with time (because you improve) instead of harder (because their is no competition).

So the solution for the goal dilemma is simply this: choose altruistic goals and you can win really big without having to dispense superhuman effort. Creating win-win situation enables you to accomplish things that you will be really proud of, even surprised that you can do it.

Simplifying a theory by Martin Seligman, I think that human happiness is a combination of pleasure (think "sex on the beach", be it the cocktail or the real thing), flow (doing something really fun, which uses your skills and strengths, no matter if it's useful work or you do it just for fun), and finally accomplishment. The great thing about audacious goals is that they can focus your learning and doing in a way that creates flow and is also positively challenging, while at the same time, the accomplishment will be really meaningful and provide you with an emotional bonus that you can build on to do even more terrifying stuff (and have more fun in the process).

As the most basic example of win-win, consider investing more time into friendships and get less heated up about the dating game. Friendships (except for exclusive concepts like "one and only best friend for life forever") are win-win arrangements by their very nature. Friendships benefit you, your friends, and also your other friends and friends of friends because like-minded people tend to cluster together and thus meet more like-minded people.

Another basic example is to focus less on making money once you have enough to afford the basic necessities of life and all the simple pleasures. Think of mixing your cocktail yourself instead of buying it in an exclusive bar. Remember that making stuff is fun -- it creates happiness in and of itself.

Here's a stunning insight: Studies show that the happiness of people in developed nations did not increase in the last decades although their monetary wealth increased a lot. More intriguingly in another study, people in different countries were asked what level of income they thought would be sufficient for them to lead a happy, normal life, being able to afford all the things they really want (but not useless luxuries). The values seemed to be consistent in each countries, but different when comparing different countries, so the researchers concluded that this "happiness income" is probably influenced by culture. But there's one thing the researches didn't see: the happiness income was actually the same in all those countries after normalizing with the average income of each country. It turns out that people quite consistently think they will just need a little more than the average! And of course, this goal can never reached by all people! It is a win-loss game which makes us all work harder, pushes the economy forward, creates inflation, furthers consumerism and materialism... but it does not make people more happy.

Now, I don't want to talk anybody out of having a great career, especially in a field that creates a lot of value for humanity while still creating a big paycheck for you. But remember that your personal scale of accomplishment money-wise is anchored at the industrial average... which goes up just as you are trying to beat it. Surprise victories might happen, but they will not be big and maybe not lasting either. If, however, you focus on other goals, think win-win, you're much more likely to be surprised by your own success.

Tunnel-Vorhersage für Berlin: von der U-Bahn zur Tram

Prognosen sind ja immer schwierig, besonders wenn sie die Zukunft betreffen. Ich will mich trotzdem mal an einer versuchen, weil sie mir relativ offensichtlich erscheint, aber die Aussage noch nicht prominent im Internet vertreten ist.

Ich glaube, der Tunnel der heutigen Berliner U-Bahnlinie 4 (Knoten Nollendorfplatz bis Ringbahn Innsbrucker Platz) wird im Laufe der nächsten zwanzig bis dreißig Jahre auf Straßenbahnbetrieb umgebaut so dass eine direkte Verbindung zum Potsdamer Platz (wahrscheinlich über das Kulturforum) hergestellt wird.

Hier nun ein paar Hintergründe, die zu dieser These führen:

1. Da die Linie U4 sehr kurz ist und hauptsächlich durch Wohngebiete führt, hat sie relativ geringe Passagierzahlen (vergleichbar mit einer Buslinie). Diese Zahlen rechtfertigen die Betriebskosten durchaus, jedoch bei notwendigen Sanierungen stellt sich die Frage nach der Rentabilität derselben. 
2. Der Berliner Senat rechnet aufgrund stagnierender Bevölkerung und zunehmender Vergreisung mit einer leichten Abnahme des Verkehrsbedürfnisses in Berlin. Abgesehen von der Kanzler-U-Bahn (im Bau befindliche U5) wird es in den nächsten Jahrzehnten wohl kaum U-Bahn-Erweiterungen geben. 
3. An der Straßenbahn wird hingegen fleißig gebaut. Außer dem aktuellen Großprojekt am Hauptbahnhof einen neuen Endpunkt mit Abstellanlage für die Linien M6, M8, M10 und 12 zu schaffen, soll nach Fertigstellung der U5 im Jahr 2016 insbesondere eine Straßenbahnverbindung vom Alexanderplatz zum Potsdamer Platz durch das neu gestaltete Klosterviertel und die Leipziger Straße (wo schon seit den 90er Jahre StraB-Gleise für diese Verbindung eingebaut sind) realisiert werden. (Zum Klosterviertel siehe Bebauungsplan des Senats und die exzellente Darstellung der Gesellschaft Historisches Berlin.)
4. Grundsätzlich wurden viele Planungen für U-Bahn-Erweiterungen einfach in Erweiterungen der Straßenbahn umgeschrieben. So besteht bereits das offizielle Projekt zwischen Hauptbahnhof und Turmstraße nicht (wie seit den 50er Jahren geplant) die U5 zu verlängern, sondern jetzt eben die Straßenbahn.
5. Auch zwischen Potsdamer Platz – Kulturforum – Magdeburger Platz und Nollendorfplatz / Wittenbergplatz besteht eine "Freihaltung" für eine zukünftige U-Bahnlinie, damit diese in ferner Zukunft einmal gebaut werden kann. Die in Planung befindliche Straßenbahn-Linie vom Alexanderplatz zum Potsdamer Platz soll vorerst am Kulturforum enden. Eine Fortsetzung Richtung Nollendorfplatz erscheint hier sehr sinnvoll, allein schon aufgrund der dortigen Umsteigemöglichkeiten zu den Linien U1, U3 und U4. (U2 besteht ja schon am Potsdamer Platz selbst.)
6. U-Bahn und Straßenbahn basieren auf sehr ähnlicher Technik (z.B. Gleichspannung 600 bis 750V, nur eben einmal mit Oberleitung und einmal mit Stromschiene), folgen sehr ähnlichen Vorschrift (BOStraB) und wurden schon in vielen anderen Städten im Rahmen von Stadtbahnsystemen erfolgreich kombiniert. Eine Erhöhung der Fahrspannung der Straßenbahn von 600 auf 750 V wurde zum Beispiel in mehreren Städten schon durchgeführt. Auch wenn in anderen U-/StraB-Netzen beide Systeme eine Oberleitung verwenden, so ist die Stromschiene kein unüberwindbares Problem. Was die unterschiedlichen Abmessungen der Fahrzeuge angeht, gibt es bereits viele erfolgreiche Beispiel für die Überwindung der unterschiedlichen Fahrzeugbreiten und Bahnsteighöhen.

All das zusammengefasst, lässt sich also durch den Umbau auf Straßenbahnbetrieb die vorhandene Infrastruktur besser und flexibler ausnutzen, insbesondere weil durch längere umsteigefreie Verbindungen mehr Nutzen für die Fahrgäste entsteht.

Ich möchte keinerlei Detail-Vorhersage treffen, (z.B. zu Linienverlauf, technischer Realisierung, Fahrzeugtypen, ...). Aber damit sich der Leser das Projekt besser vorstellen kann, hier noch ein paar weitere Informationen. Ohne einen Bezug zur aktuellen Straßenbahnlinie M4 konkret vorherzusagen, nenne ich die vorhergesagte Linie im folgenden einfach mal M4p. Klein "p" für "prognostiziert". :-)

1. Die Kosten für den Umbau eines U-Bahntunnels auf Straßenbahnbetrieb liegen vermutlich in derselben Größenordnung wie für den Neubau einer Straßenbahn. Es müssen die Bahnsteige abgesenkt (oder die Gleise in den Stationen erhöht) werden, sowie die Stromversorgung auf Oberleitung umgebaut werden. Wenn Berlin experimentierfreudig sein will, können natürlich auch Straßenbahnen zusätzlich mit dem Stromabnehmer der U-Bahn ausgestattet werden, wodurch sie dann sogar Strecken gemeinsam mit U-Bahn-Fahrzeugen benutzen können. (Betriebsrechtlich gelten U-Bahnen ohnehin als Straßenbahnen, so dass eine gewissen Grund-Kompatibilität besteht.)
2. Irgendwo zwischen Kulturforum / Botschafterviertel und Magdeburger Platz / Genthiner Straße wird eine Tunneleinfahrt gebaut. Wie man sich auf Google Maps anschauen kann, gibt es hierfür ein verschiedenen Stellen Platz. Für eine ökonomische Lösung kann die Straßenbahn den Landwehr Kanal noch oberirdisch überqueren. Eine unterirdische Querung ist aber auch möglich, falls (wie unten beschrieben) am Magdeburger Platz eine unterirdische Straßenbahn- und U-Bahn-Station gebaut wird.
3. Um das Fahrgastaufkommen zu bewältigen, müssen natürlich recht lange Straßenbahn-Fahrzeuge (bzw. Straßenbahn-Züge) eingesetzt werden und die Taktabstände müssen entsprechend kurz sein. Die aktuelle U4 wird ohnehin mit für U-Bahn-Verhältnissen recht kurzen Zügen betrieben und der Takt ist mit maximal fünf Minuten (Hauptverkehrszeit) auch recht gering. Sollte sich auf dem Tunnelabschnitt der neuen Linie Innsbrucker Platz – Potsdamer Platz – Alexander Platz – Nordost-Berlin besonders hohes Fahrgastaufkommen ergeben, kann dort der Takt auch durch zusätzliche Verstärkerfahrten noch erhöht werden. (Dies sei erwähnt weil im Tunnel kürzere Takte gefahren werden können als auf einer auch von PKWs genutzten Straße, da sich weniger leicht ein Stau bilden kann.) Falls sich eine Straßenbahn aus Richtung Potsdamer Platz am Nollendorfplatz verspäten sollte, kann so stattdessen ganz pünktlich ein Pendelzug am Nollendorfplatz Richtung Süden einsetzen und die Takt-Lücke füllen.
4. Unter der Genthiner Straße haben Stand Heute die U-Bahnlinien U3 und U4 eine gemeinsame Kehranlage. Hier bestehen viele Möglichkeiten, wie diese von der vorhergesagten Tunnelstraßenbahn genutzt oder umfahren werden kann, auf die ich hier wegen Platzmangels nicht weiter eingehen möchte. Natürlich gilt zu beachten, dass die Baukosten für neue unterirdische Kreuzungsbauwerke im Vergleich zur Straßenbahn sehr hoch liegen, so dass hier nach einer ökonomischen Lösung gesucht werden muss.
5. Natürlich werden die Baumaßnahmen alle so durchgeführt, dass die Freihaltungen für die geplante U-Bahn-Strecke vom Potsdamer Platz (ungenutzte U-Bahn-Station im Regionalbahnhof) über das Kulturforum / Botschafterviertel und den Magdeburger Platz zum Wittenbergplatz alle erhalten bleiben und dort irgendwann in ferner Zukunft, falls der Bedarf sich ergeben sollte, eine U-Bahn gebaut werden kann. Eine Möglichkeit auf die Zukunft hinzubauen und gleichzeitig das Problem mit der Kehranlage zu lösen, würde darin bestehen, die U3 ab Wittenbergplatz in einem neuen Tunnel bis Magdeburger Platz zu verlängern, wo sie eine von der M4p unabhängige Kehranlage erhält. (Am Wittenbergplatz würde ein weiterer Bahnsteig angelegt, der schon bei Inbetriebnahme 1913 vorgesehen war.) Da der vom Nollendorfplatz kommende Tunnel unter der Genthiner Straße ohnehin schon sehr nahe an den Magdeburger Platz reicht und möglicherweise der Abstand für den Einbau einer Rampe zu kurz ist, wäre auch vorstellbar unter dem Magdeburger Platz einen mehrgeschossigen Umsteigebahnhof (ähnlich den unteren beiden Geschossen des Nollendorfplatz) zu errichten, in dem die Straßenbahnen der M4 auf der einen Seite und die U-Bahnen der U3 auf der anderen Seite halten. (Eine Etage Richtung Süden, die andere Richtung Norden.) Natürlich wäre diese Lösung im Vergleich zu einer reinen Verlängerung der Straßenbahn durch den U-Bahntunnel wesentlich teurer. Es könnte sich aber als ein tragfähiger Kompromiss zwischen U-Bahn-Befürwortern und Straßenbahn-Protagonisten erweisen, da in beide Verkehrsmittel investiert wird und weil diese Lösung beide Netze fahrgastfreundlich verbindet, jedoch betrieblich getrennt hält. D.h. jeder Gleisabschnitt wird entweder nur von U-Bahn oder nur von Straßenbahn benutzt. Damit könnte die Fahrzeug- und Strecken-Technik von U-Bahn und Straßenbahn weiterhin unabhängig bleiben.
6. Wer mir bis hierher folgen konnte, hat noch eine weitere, noch verrücktere Bonusidee verdient. Die Langfrist-Planung für die U-Bahn sieht vor, dass die Linien U1 und U3 zu einer Linie U1p Dahlem ‒ Warschauer Straße zusammengezogen werden, so dass der übrig bleibende Abschnitt Uhlandstraße ‒ Wittenbergplatz für die Strecke Richtung Potsdamer Platz genutzt werden kann, welche ich hier mal M3p nennen will. Wenn der vorherige Punkt (U-Bahn-Station Magdeburger Platz) umgesetzt wird, dann haben die Linien U1p und M3p am Wittenbergplatz auch getrennte Bahnsteige. Man könnte also die M3p ebenfalls zur Straßenbahn umbauen. Dies würde ermöglichen auf dem Kurfürstendamm hinter der Uhlandstraße eine weitere Tunnelrampe einzurichten und die Straßenbahn wieder auf dem Mittelstreifen des Ku'damms fahren zu lassen. (Da wo in der Mitte des Ku'damms Heute PKWs parken fuhr ja früher schon die Straßenbahn. Das ist ganz ähnlich wie in der Osloer Straße und Seestraße, wo die Straßenbahn auch ein paar Jahrzehnte verschwunden war und dann wieder auftauchte.) Die Station Magdeburger Platz würde dann als Verzweigung der beiden vom Potsdamer Platz kommenden Linien M4p und M3p dienen. Dort würden dann nur Straßenbahnen verkehren, und für den Wittenbergplatz würde das oben schon erwähnte Prinzip gelten: fahrgastfreundliche Verknüpfung, betriebliche Trennung. Wenn man diesen Punkt schon von vornherein umsetzen möchte, so kann der Abschnitt Wittenbergplatz ‒ Magdeburger Platz auch oberirdisch gebaut werden. Für eine Tunnelrampe ist zum Beispiel auf der Straße An der Urania genug Platz vorhanden. Dies wäre um einen feinen Zigmillionenbetrag preisgünstiger, hätte aber den Nachteil, dass eine zusätzliche Tunnelrampe Platz im urbanen Raum verbraucht. (Während in der anderen Lösung eine gemeinsame Rampe der Linien M4p und M3p zwischen Magdeburger Platz und Kulturforum ausreichen würde.) Auch in diesem Fall bleibt die Möglichkeit erhalten, die M3p irgendwann auf Voll-U-Bahn auszubauen und die am Potsdamer Platz und Adenauerplatz schon vorhandenen Tunnelstationen zu nutzen.

Wie man sieht, gibt es viele Möglichkeiten, den Tunnel der U4 an die Straßenbahn anzubinden und dabei das restliche Netz betriebsfähig zu erhalten bzw. sinnvoll zu ergänzen. Für welche dieser Möglichkeiten sich Stadtverwaltung, Politik und BVG sich irgendwann entscheiden, kann ich Heute nicht vorhersagen. Aber eines erscheint mir als recht wahrscheinlich Hypothese: in zwanzig bis dreißig Jahren wird die Straßenbahn den Tunnel der U4 nutzen oder die verantwortlichen Stellen denken zumindest ernsthaft darüber nach. 

when cars are autonomous, taking a cab is cheaper than driving with your own car.

Maybe this is so obvious that I don't even need to write it. Maybe it's also still a bit too far into the future and too much science-fiction.

But autonomous (or self-driving) cars are slowly turning from an object of research into a reality of engineering. Currently, where it is allowed to drive them, it's only for purposes of research and development. But once a state or country will allow them for just transport, many others might follow in quick succession. (Some technologies are adopted very quickly, while others need a very long time until they are in widespread use or until they have displaced their predecessor technology. But that's a topic for another post.)

Now, let's just assume that self-driving cars will be available at some time near or far. Let's assume that they will be more expensive than people-driven cars, but that the price difference is not more than the relative difference between a current cheap and moderately expensive car. People will have the choice to buy and drive either one. And for many who can afford it the self-driving car will be the choice, because it gives them a lot of extra time to spend during their commute. Let's also assume that there will be a similar choice for taxis: you can get a self-driving one or get one with a driver. Since for the self-driving taxi, no driver needs to be paid, it will be cheaper than a person-driven taxi. Also, since there is no person to watch the passenger and make sure they are paying and not messing the car up, it's possible that self-driving taxis will require some sort of registration of the passengers just as is the case for car-sharing services now. Indeed, the difference between car sharing and taxis will blur when both are self-driving.

If one has to register to use a self-driving taxi service (for example, by requesting a RFID customer card which is linked to your payment details and name/photo), this is just like for car-sharing, only that a lot more people will do it. That's because unlike traditional car sharing where you need to go to a station to pick up your shared car and also leave it a station, the self-driving taxi (or next-generation shared car) can drive autonomously to pick you up and can also disappear on its own when you don't need it any more.

It's those last two features which previously have hindered the adoption of shared cars (because you need additional transport to get to stations) and which will make the self-driving shared car even more useful than your own car. First, because you don't need to have your own parking spot, which makes live a lot easier if you live in a urban setting without underground parking or other reserved parking space. Second, you don't need to find parking at your destination, which is two advantages at once: A - you can get off wherever a taxi could let you get off, which is often much closer to your destination than a parking spot would be, and B - you save all the time to find a parking spot, park the car, and pay for the parking (if needed).

So there: we'll have the luxury of taking a taxi at the price of taking a shared car, which is much cheaper than having your own car. Just think of it: the shared car will transport many other people over the course of the day, all getting the luxury of a taxi drive and contributing to the maintenance and purchase cost of the car. Since the car is used much more, it will be amortized much quicker, so shared cars will be upgraded to newer models and the latest technologies more often than people would buy a new private car.

So there you have it ‒ self-driving shared cars might replace a lot of privately-owned cars ‒ especially for people who don't have private parking space and even more so for people who already use a mix of public and private transportation. (Missed your last commuter train or need to do some shopping on the way home? Just take a self-driving taxi!)

I am already fantasizing what could be done to all this reconverted car parking space in our cities ‒ more green, more life, more socializing. Maybe even happier people?