Marco Chitti Profile picture
Aug 2, 2021 β€’ 11 tweets β€’ 8 min read β€’ Read on X
1/ This is a short, mostly visual thread about a great piece of urbanism: Turin's multiway boulevards.

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2/ multiway boulevards are one of the most interesting invention of 19th c. city planning, a first attempt to create thoroughfares to facilitate circulation in growing "paleo-technic" metropolis

In Italy, Turin is the city that designed its growth around them more than any other
3/ taking various shapes, width and configurations, most of them have an important feature: planted medians sepatarating through traffic of trams/cars from side local acces lanes intended for local slow traffic, parking.
4/ one of the most interesting is Corso Francia, a very long straight line connecting the city center with the distant Rivoli castle. Baroque Le NΓ΄tre-sque large scale landscape at its peak.5
5/ despite its monumental lenght, corso Francia has a very nice, intimate neighborhood street feeling, especially the section redesigned after the construction of the metro line that run under it.
A greened median separtes the 2-lane*dir carriageways
6/ the tree-lined medians are used for parking and other functions as bike racks or bus stops, accessible from the side access roads, where speed is limited to 20km/h + a slightly raised bike lane and large stone paved sidewalk protected with bollards
7/ side streets intersections with access lanes are treated with traffic calming features like raised intersections, pavings and other safety design features
8/ metro access are simple and well integrated into the street design, with safe raised crossing across the central car lanes at main squares and other nice fixtures.
9/ tree canopy is so ubiquitous and pleasant that one forgets about architecture: all kinds of buildings spanning more than 100 years integrates without much contrast or "harm to the neighborhood character"...
10/ The outer section of corso Francia didn't get the same treatment (no $$$) and it shows (more cars, narrower sidewalks).

Other boulevards are too wide, like the one built atop the passante city rail tunnel, and it feels like a slightly nicer urban freeway with coll lights.
11/ multiway boulevards are a good element of design for modern cities and north-american urbanism knows them already quite well, see Allan Jacobs's "The Boulevards Book".

But remember that it's hard to get them right by design and that the Devil is in the details.

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More from @ChittiMarco

Aug 1, 2024
It's always interesting to note how, unsurprisingly, the history of transportation planning is nested in the shifting larger paradigms of urban planning.

The only two sizable "greenfield" outlying sections of Frankfurt U-Bahn follow two different paradigms of urban integration. Image
The only greenfield section part of the overall pre-metro scheme built in the initial phases run either underground or in a freeway median, within an area of interwar (Romerstadt) and postwar modernist development.
Grade-separation was the "gold standard" for everything back then


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The 2000s addition to the U-Bahn network, serving the large greenfield development of Riedberg, whose own urban design reverts to the "traditional" perimeter block, run as a tramway on a street tree-lined median with signal-controlled intersections. Quite the change of paradigm.


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Read 5 tweets
Jul 31, 2024
One of the reasons why French tramways tend to be relatively slow is that they often have very curvy and zigzagging alignments. There are two main reasons for that, one linked to the history of urban development in France, the other to how and when French networks developed. Image
The historical reason is that France, outside of Paris intramuros, it's not a country of Grand Boulevards and large urban schemes. With one of the most property owners-friendly land regimes, French cities mostly grew with chaotic street patterns during both the 19th and 20th c.
Streets, even major radial arterials, tend to be narrow until the postwar era, outside of a few isolated redevelopment schemes, such as Grenoble's 20th c. boulevards or Bordeaux 18th c. Triangle. Provincial elites never indulged in the grandiose schemes of the capital city.
Read 7 tweets
Jul 24, 2024
Not only Seattle (and many other cities) opt for mined stations in city-center areas, but they also do it in the most bloated way, with full-length mezzanines and wide off-street access shafts.

Let's look at a more sober approach to mined stations from u/c Vienna's U5


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First, the Seattle approach (veru common in NA mined stations) is to go with a large cavern encompassing both tracks, a central platform and a "full-length mezzanine, that is a slab above the platform level allowing for horizontal circulation outside of platform space Image
The wide two-level single cavern is connected to the vertical shafts via two "transepts" (mined tunnels perpendicular to the cavern), as the shafts are built rigorously off-street. Additionally, a diagonal mined tunnel can host escalators.

This isn't the approach used in Wien
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Read 10 tweets
Jul 16, 2024
Today, the much-awaited, 5, 5 km, 8 station, metro line 6 in Naples was finally (re)opened* (with limited service) after a 40+ years-long saga that is emblematic of how the bad choices and habits of the 1980s still haunt Italy today.

A 🧡


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Naples' line 6 has a very troubled history. It was initially planned in the early 1980s as the "Linea Tranviaria Rapida", an LRT-like system mixing at-grade and grade-separated segments crossing the city East-West roughly along the coast. Image
It was planned following the approval of a national law encouraging the construction of "LRT-like" systems, to be built with local and national funds with the involvement of the state-controlled IRI conglomerate, via non-competitive 30 years "concessions of sole construction"
Read 17 tweets
Jun 10, 2024
A recent exchange in here reminded me that historically there has essentially been two main paths toward level boarding of mainline rail.

The prevalence of one type or the other in a country depends a lot of when and how the railway became a commuter-oriented mobility tool.

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The 19th c. railways had very low platforms, just slightly higher than the tracks, either in wood, masonry, or simply a stone curb filled with gravel. Essentially, a glorified sidewalk.
That was ok for a railway with sparse traffic and generous dwelling times.
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But platforms that require passengers to climb several steps to get into the trains, whose boogie-mounted floors are often >100 cm high above the track, are unfit for the need of the higher frequency, high traffic railway catering to the hinterland-to-city commuters.
Read 18 tweets
Jun 5, 2024
How does Zurich achieve consistent running times and an elevated average speed on its legacy tramway network despite the fact that it's not fully running on dedicated lanes?

An example of urban integration and conflict management strategies along a segment of line 3

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Tramway line 3 covers the 4.3 km, 11-stop section between its terminus at Albisrieden to Sihlpost /HB in 16 minutes, with consistent running times throughout the say, averaging a pretty good 16 km/h speed.

How does it achieve these performances? Image
Let's start from line 3 western terminal loop, where the tram enters the general circulation protected by a traffic light and then continues along the central lanes of a suburban street. All lateral streets yield to the main arterial which is a "priority street" Image
Read 13 tweets

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