The Fast Way to Build Subways: Cut and Cover

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Subways used to be built in just a few years, and they used to be built with cut and cover construction! But what is cut and cover, and should we go back? Find out in today's video.
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Ever wondered why your city's transit just doesn't seem quite up to snuff? RMTransit is here to answer that, and help you open your eyes to all of the different public transportation systems around the world!
Reece (the RM in RMTransit) is an urbanist and public transport critic residing in Toronto, Canada, with the goal of helping the world become more connected through metros, trams, buses, high-speed trains, and all other transport modes.

[@RMTransit]

If you want to hear more about how different construction approaches can send a project off the rails, read my latest blog post here: rmtransit.substack.com/p/the-eglinton-crosstown-is-delayed

[@fredashay]

I suspect that TBMs are used instead of C&C when C&C would be the better option is because of NIMBYs...

[@Real_Tim_S]

C&C gets a lot of flack due ot the piling required to do the ditch walls. Reaction piling systems (such as the silent piler by Giken, no affiliation) have done away with the large space claim and environmental impact typically associated with piling projects. I recently got to see a demo of this type of system stabilizing a property by a river and it was truly quiet - with a sound attenuated hydraulic power unit/generator as the biggest noise source, one could still have a confortable conversation without yelling 20 feet away. The loudest sound in the site was the warning beepers from the trucks bringing in the sheet piling. Smaller TBMs (microtunneling, likek those produced by Herrenknecht and others - again no affiliation) still like to have launch pits which will require some cut-cover/trenching. Each tool has its job.

[@frafraplanner9277]

I just ordered that book you recommended "How Big Things Get Done" and it's the best thing any urban planner or civil engineer can read to learn how to get projects done on time

[@bluebox2000]

Tunneling for East Side Access, the 2nd Avenue subway and Crossrail were all mostly trouble-free and the fast part. It's the installing of track, wiring and life safety systems that seems to cause years of delay and budget overruns. Whether a new tunnel is cut-n-cover or a TBM to avoid utilities, isn't the problem. Very bad management is why we can't have nice things anymore.

[@gregessex1851]

@@fredashay TBM’s are often cheaper and certainly less disruptive. Cut and cover is viable for short sections where there is a usable corridor that can tolerate years of extreme disruption

[@deanlemckeevans]

cut and cover also provides the city an opportunity to improve other infrastructure that goes under a street like water pipes

[@bearcubdaycare]

Like the wooden slats strapped together that Boston's Big Dig found (with water flowing through). 😂

[@benlever3172]

That's a bit of a double-edged sword, though - cut-and-cover means you HAVE to revamp any under-road infrastructure, which can add a lot to the costs (particularly when you have to relocate things like high-pressure gas mains)

[@RMTransit]

That’s true but generally I think bundling like this is a bad idea

[@williamerazo3921]

@@benlever3172 should be done anyways. Yeah let’s drink from lead water pipes

[@georgobergfell]

​@@williamerazo3921 Flint vibes coming up

[@FalconsEye58094]

This is how something like 90% of New York stations were built, some people wonder how so many were built giving it takes so long to make just one today.

[@stthecat3935]

Then I guess the problem is the tracks and tunnels since the alignment requires tons of urban and environmental planning and trade-offs

[@RMTransit]

Yes! But it’s not just that, as I discuss :)

[@RBzee112]

Most of the remaining elevated lines were built before those neighborhoods were fully developed.

[@williamerazo3921]

Most of NYC was built like this in less 40 year time span. Only China can do something like this at a fast pace

[@scottydude456]

It always blows my mind how shallow the 1 train is, especially at 59th street where you can can see people walking on the street from the giant entrance on the uptown platform

[@wilfstor3078]

Whenever my parents question why it takes so long to build subways these days I always comment that "It's no longer acceptable for an Italian immigrant to die every kilometer any more" which always makes them realize how far safety rules have come in their lifetimes...

[@saltysea3626]

It's nice that your parents appreciate your interest in Transit, my mom just yells at me and tells me to get a job

[@Bertramel]

@@saltysea3626 Depends on Your age

[@hypernewlapse]

Idk lots of countries build transit fast and safe (spain turkey for example)

[@SKAOG21]

@@hypernewlapse This ^^^. Countries are able to build quick without compromising safety.

[@gregessex1851]

I bet it was more than one death per km.

[@francoiss6911]

The Melbourne Metro Tunnel used cut and cover for its stations but it built huge sheds over the stations so that dust and sound were dampened significantly. It also allowed them to add windows in so people could see the stations progress and arts on the sides while using TBM’s in between stations. It was a really nice idea and you really couldn’t tell there was so much construction happening right under you.

[@RMTransit]

I thought at least some of them were mined?

[@martinhesse8679]

@@RMTransit The 2 CBD stations only access shafts were build, with mostly sheds over them, and the section of the station between the shafts were mined. The other 3 stations or mostly cut and cover.

[@MrLincoln87]

@@RMTransit I think they're doing cut and cover for the stations in ... Auckland NZ, and TBMs for the lines

[@neolithictransitrevolution427]

With the REM and Ontario line, Toronto, Vancouver, Montreal, and Ottawa will all have built elevated transit lines in the last decade. A good sign for building experience and things to come.

[@RMTransit]

In some ways yes, but the prices are still going up!

[@ethanstearns2352]

This video is absolutely correct, but also the issue with North American transit construction is not just the construction methods, it's everything else. The Maryland purple line for example uses cut and cover for its underground portions, a mostly above ground preexisting right-of-way, and its still been delayed over and over again!

[@Steve-tj9on]

I thought they are using boring machines like in Bethesda. I'm be glad when the crossing of Kenilworth ave for the Riverdale elevated station. I'm tired of driving passed it and seeing the same thing. Seemingly not much seen work being done.

[@ruedelta]

@@Steve-tj9on I've lost all hope for DMV projects anyways. Silver line started back in 2007 for context, and it didn't finish until just recently...

[@justsomeguy5103]

I think this video vastly underestimates the cost of cut and cover. It might have been cheap to do in the olden days, but these days it's not as simple as closing the road and deploying the largest excavators you can find. There are fine webs of infrastructure for power, internet, water/sewage etc. under any moderately urban street. Just working around that infrastructure hampers excavation efficiency drastically. If you need to move/realign a bunch of stuff that crosses through were your tunnel is going, that adds even more to the bill. Not to mention having to stabilize the sides where there is no space to dig at an angle - which is insanely expensive. Tunneling is ridiculously expensive indeed, but apart from geological factors, you are unlikely to meet any surprises.

[@michaelimbesi2314]

That’s because these days, it’s legal for any NIMBY to sue to stop a project using BS environmental concerns

[@RMTransit]

Of course, the project organization is a huge issue! See the pinned comment for more

[@MultiRanman]

The cut and cover method seems to work best is situations where, naturally, want to go in a straight line under a street. It’s probably the best option and why cities used it initially, especially under many streets in NYC.

[@Madwonk]

yeah, this. Realistically it's just not practical on many routes. LA is a great example as it uses both in different situations!

[@tramcrazy]

A good example I think is London, the old sub surface lines were built with cut and cover but they completely dug up the streets to do it. I’m not sure people would accept that now. Also cut and cover is very very hard to do where buildings are present.

[@michaelmains6785]

As a tunnel designer who works on transportation projects I think this is an excellent, well articulated opinion by someone who clearly has a deep understanding of subway construction. Well done.

[@Xsiondu]

As a person who lives in an area with 5 tunnels crossing major bodies of water i was wondering if you know how they are doing on the new Hampton roads bridge tunnel? Serious question. Are you working with that one or do you know anyone who is?

[@scottydude456]

One construction project in the US that could totally be done with cut and cover is the Roosevelt Blvd Subway in Philadelphia. Alan Fisher has a good video on it that I would suggest watching

[@unlapras9365]

I notice that in my country (France) cut and cover is no longer an option, even where it would be technically possible. We just build everything with TBMs regardless of whether it's justified or not and stations become needlessly deep and expensive to build. Unfortunately I think the fear of NIMBYs is the main explanation. In Paris a very short cut and cover section had to be built for line 1's extension just to launch the TBM and yet the whole project might be cancelled because locals refused it.

[@amdsemporn6018]

In my city in Germany, cut and cover is a huge pain, because they will definitely find remains of the romans from 2000 years ago, halting the complete operations

[@German_CG_Artist]

and thats just the harmless stuff. unlike most cities in north america, in german cities you can and do ocasionaly find unexploded ordinance from the second world war.

[@vlaardingerrr]

Another reason for not choosing cut and cover is that u have to move all the underground infrastructure as well. Sewer, phone, electricity and water. The hardest and most expensive to move is the sewer pipe, the fall must be consistent, sewer doesn’t like going uphill/around the new metro line. For the Canada line in Vancouver; probably the underground space had been “reserved” for a few decades in anticipation for the metro line. Because of the reserved status the underground space have been kept empty. De streets which are wide enough for cut and cover are most of the time the bigger access roads. Most of the time underneath those roads are the main pipes and cables for the whole neighborhood. Keep in mind a metro line travels a long distance through the city. And Because of the size and the inconvenience of not having water/power/sewer in the whole neighborhood the builder have to move the pipes and cables multiple times. They know there is something underground, but they don’t know where precisely and how deep. The drawings they do have are old, when the neighborhood was being build. Those old drawings are not that detailed and also outdated. Some changes which have been made over the years have been lost. The other problem with old drawings is that u can’t read them because it’s copied/edited and printed too many times. And with the lack of detailed information try to make a plan for moving those cables and pipes multiple times. And try to make a new connection with a sewer or water pipe from 1960, it probably will fail. This all is way too hard and expensive. It’s much easier and cheaper to dig a square hole once in a while for a elevator shaft.

[@AaronSmith-sx4ez]

Cut & Cover is definitely the gold standard for rapid transit expansion and I wish it were used more. But one downside of building under streets, is most modern cities put most of their utility conduits there (sewage, water, fiber, electric, gas, storm water, etc). So the main cost usually isn't ripping up the street and digging a hole, but relocating all those utility connections which can be costly. But in many cases IMO it can be worth it because cut & cover is so much more efficient. NY doesn't have the rapid transit system it does today if not for cut & cover. If they originally built deep tunnels the walk times to the stations would have been too much and far fewer people would have used it.

[@bearcubdaycare]

Tunnel boring isn't so horrifically expensive anymore. The Elizabeth Line spent a small fraction on boring, and most on stations. All those utilities, and disruption to the city, can be reasons to prefer boring in many cases. (An aside on moving utilities, the Big Dig in Boston came across centuries old water lines formed by wooden slats strapped together...with water flowing through them.)

[@AaronSmith-sx4ez]

@@bearcubdaycare But the problem with deep tunnels is deep stations and long walk times. Long walk times are a hidden killer for rapid transit systems. In MY, many stations are just a 30-40 second walk from the surface...which is a hidden reason NY has a such a popular transit system. On the flip side China is completely oblivious on this issue and crazy long walk times (and security) will hurt many of China's rapid transit systems from reaching their true potential.

[@mancubwwa]

Tunel borinfg went a long way since the 50's or even the 90's The TBMs that dug Warsaw Metro's line 2 in 2010s were moving roughly 5 times as fast as the one that dug non-cut and cover parts of line 1 in 1990 and early 2000s. Cut and cover still can be faster given favorable terrain, but a lot hangs on other factors.

[@RMTransit]

Idk! Vancouver has under road utilities and managed to figure it out!

[@andrewmasin5787]

If so, how did London ever survive the switch to deep level tubes?

[@jan-lukas]

As always: build stuff overground! It's always cheaper than building tunnels

[@apexhunter935]

Elevated or grade-level trackage?

[@Jason-gq8fo]

Unless there is nimbys in the way haha

[@ianhomerpura8937]

@@apexhunter935 grade level is much cheaper, but eliminate at grade crossings as much as possible. That is how Japan managed to still operate most rural lines.

[@ianhomerpura8937]

@@Jason-gq8fo if they are simply reactivating lines, they can't do much I guess

[@bearcubdaycare]

Through whose neighborhood?

[@paulallenpatriarca]

I started watching your videos 4 years ago and now, I'm a graduating railway engineer in my country. Thank you for always giving me valuable insights.

[@nicolasblume1046]

An important factor is street width: If the street is quite narrow, cut and Cover might not be feasible for the whole route.

[@n.bastians8633]

There are cut and cover subways beneath narrow streets where the builders decided to stack the two tracks on top of each other. It's definitely possible.

[@MarioFanGamer659]

@@n.bastians8633 Good examples in Frankfurt: Merianplatz, Höhenstraße, Bornheim Mitte and Leipziger Straße. Incidently, all but the latter (which is below its namesake, Leipziger Straße) are located on the same street (Berger Straße) but they all are one-way streets with street parking at most.

[@Skip6235]

So annoying that the Broadway Subway in Vancouver is being tunnel-bored. It goes right down one of the widest streets in the city and could have been done so much cheaper and faster (probably could have gone all the way to UBC for the same price) But the NIMBYs who hated the Canada Line construction convinced the Province to use TBMs instead

[@ianweniger6620]

cnc at Main-Quebec, Yukon-Cambie, Maple-Arbutus...

[@fallenshallrise]

Must be nice to have a little condo and a car and have the city bow down to you at all times. We have to tunnel a hole through the ground not like the whole city is a grid and there is 4th, or 10th, or 12th, or 16th, or 25th to head east or west. Broadway could also EASILY have dedicated bus lanes going both directions but instead buses have to wait in traffic so that 15 people can park on the street instead of using a side-street or a parkade.

[@street_ruffian]

RM Transit more like RM Trams in Tunnel lover. You are the number 1 tram in tunnel fan

[@Globalurb]

I agree, cut and cover is a method among many others. Besides disruption (see initial Yonge subway construction trauma), theres is also a cost to deal with existing underground infrastructure. Builders are forced to relocate, temporarily support or be extremely careful with (using extremely expensive methods) existing infrastructure.

[@Seibanori]

Well, I think the moral of the story didn’t just apply to ‘how to build subway or things’, rather it applied to basically everything. One of the fun fact that me as a Asian who lived in NA especially Toronto for 7 years, found interesting about is that North American are more likely to be radical in adopting idea or method about everything. In this case, the traffic for example, they used to be ‘we gonna build huge highways and tremendous amount of cars that public transportation will no longer be needed’, and now a lot of people are like ‘we want walkable city so much that we should remove all the highways and cars and make everything car-free’. Well, my hometown or a lot of Asian countries have some of the best public transportation in the world, let’s say Tokyo for example, which contains 3-40 million population in that city but somehow manages to have a relatively decent traffic through the days. And the reason behind that is how complex the Tokyo transit network is. You see Tokyo not only has the best public transportation in the world, but it also has the best infrastructure in the world. Tokyo circular route serves the best to transport cars so that whoever wants to drive a car can do so as well as the people who want to take the transit or walk. A city is never meant to be built by only one method to move people around, rather all the different methods are needed. So it’s never like ‘we should build more transportation and stop highway’, but it’s more like ‘we should build more public transportation as well as highways, especially city circular routes to fix the traffic’. And also, whenever building a transportation, I think it’s very important to make it separate from roads and cars so that it serves its purposes properly, which means trams in DT area like Toronto is just utter rubbish and should be replaced by subways or sky-train. Trams can only fit its rule the best when it’s built in densely populated suburban areas like Scarborough or North York. And also, circular routes really really works better than highway go through DT area, it’s been proven in many Asian and European cities and I think it’s exactly what Toronto really needs right now.

[@trevorvanderwoerd8915]

I think part of the reason why north americans (who are transit fans) will go to the extreme of wanting no new highway building is because north america already has tons of highways - we don't need more. Toronto for example has 3 east-west highways and 4 north-south highways. As far as circular highways, you seem to be unaware that the vast majority of cities in US & Canada already have them. Toronto's is the 407 (it's a half circle because of the lake, but whatever), and it's a huge failure on a regional level because the toll is too high. And the toll is too high because the Conservative provincial government of the 90s are idiots and sold it to overseas investors who don't care if the city functions well. I call it a failure because parallel routes like the 401 or Highway 7 have still needed to be widened or turned into highway-like arterials. Now there is demand for Highway 413 which is yet another highway parallel to the 407, all because the 407 never worked and the province never provided a decent non-automobile way to travel east-west in the GTA other than Lake Shore GO, which is literally 15 km south of the 407. You say that Tokyo has surprisingly decent car traffic. Yes, because there is so much good transit that there is no reason to get involved into traffic congestion. Not because they built a lot of highways, but because their ratio of transit to highway & arterials is so much more tilted towards transit.

[@Seibanori]

@@trevorvanderwoerd8915 part of ur argument is true, however ‘city circular highways’ isn’t usually something that only exists just one in a mage city. Take Beijing for example, they have five and as far as I know there might be even a sixth one at some point in the future. Toronto has something very close to a city circular highway, true. However, between DT and Midtown area there are supposed to have one more highway to form something so called ‘the first circle’ to mainly serve DT area, and I’d say that the don valley highway should have the second bridge to serve the people who only passes DT but not getting to DT. There is 407 true, and it’s a big failure also true. But even including 407 as if it’s a free highway, only three highway to serve the East to West of Toronto is way too less to be honest especially for Toronto as how strange the city management is, and plus 407 is mainly served to rural suburban areas like Richmond hill or Markham. You don’t need to make a huge highway that has 20 lines in it like 401, the traffic will still be there. But what u really need is multiple highway to serve people who goes different directions and also not making any highway too over densely used. And btw, Japanese do drive, whatever the fantasy that North American have about ‘European or Asian’ don’t drive is just pure nonsense. Maybe not as much as North America, but most of us do have cars and many of us, we do drive to work. We just normally have a better and more complex transit system than you guys that whenever we don’t want to drive, we might get the chance to use another method to go to work. But it doesn’t mean we don’t drive or we hate driving. In fact, driving is a very popular culture in Japan.

[@Seibanori]

@@trevorvanderwoerd8915 I guess the whole point is that building highway does not conflict with building public transportation and the idea of relating building infrastructure with politics should be stopped. They are parallel and can be processed simultaneously. Just because we should build more public transportation doesn’t mean we should get rid of all the infrastructure. Do I support building more public transportation? I definitely do, but I do also support build more highway and improve infrastructure. And in fact, I think that Toronto, or most of the North American cities in general should get rid of Plazas and single houses so that those huge waste of land can be re-use to make a better used and more densely populated city so that infrastructure and public transportation can be better and easier to build to serve the city as a CITY instead of the typical NA city that we got now. Honestly I’d say that outside of DT and few other densely populated areas, most parts of the city are more like ‘Desakota’, if u don’t know the definition search it up. Lmao

[@lzh4950]

@@Seibanori Only the outer 2 of Beijing's 5 ring roads are completely grade separated though; the inner 3 still have at-grade intersections, but fewer in number e.g. by having underpasses/bridges

[@Seibanori]

@@lzh4950 well, that’s probably because when they built the inner 3 rings, the main land China was still in a very early development stage and they probably didn’t think that the traffic will ever gonna be that bad. And another thing is, once ur population is getting to a certain level, no matter how many highways or subways u build, the trafficking will still be there. It’s just inevitable. Take Beijing for example, it has more than 20 million population. It’s just gonna be there.

[@BBBuilds12]

I like cut and cover subways better from a user experience perspective because it tends to be much quicker to get from the surface outside of a station to the platform.

[@ViniciusSC10]

I’ve wondered why they don’t use cut and cover anymore, I think the biggest problem is the impact they have on streets and neighborhoods, completely blocking them even if for a short period of time. São Paulo also completely abandoned cut and cover, besides the fact that the first line in the city was the fastest to be build (in the 1960s). Today the only way to build here is using TBM and sure, it’s great in some aspect (especially building under the rivers and the huge number of buildings), but at same time crest huge structures and that makes building more expensive.

[@henryostman5740]

Good video, made a lot of sense. We need to remember that our toolbox has grown over the years, back in the day they didn't have TBMs and a lot of digging was done with a pick and shovel. A big problem today is all of the stuff that is buried under the street, used to be just the water lines and sewers, now we have electrical lines, telephone, cable, telegraph?, and steam lines for building heat. And, believe, a lot of this stuff isn't very well mapped, you dig and find stuff that wasn't supposed to be there. Remember too, that horse and wagon transport had a weight limit of less than ten tons, todays trucks weight that much empty. So, get a TBM and dig deeper, under the first and second layers. Then you have other problems, DC was a swamp and really still is, they just paved over it. You generally have to dig out the stations but that big hole fills up with water that you have to pump out, but dewatering destabilizes the foundations of nearby buildings, resulting in a lot more work. Your comment on transit moving a lot of people with NO pollution is like the claim for electric kars, yeah, there is no tailpipe on the train but where do they get the juice? Probably a coal fired station up the river a few miles.

[@questionmaker5666]

The pollution from EMUs is far less per passenger than an electric car, but even from renewable energy it is never absolutely zero pollution.

[@gabetalks9275]

Imagine how much faster the 2nd Avenue Subway could be completed if they just used cut and cover instead of tunnel boarding extremely deep underground.

[@walter2902]

Has this been done - a continuous cut-and-cover. Dig 10m trench in week 1. Prepare bedding and place precast box tunnel in Week 2, Grout and Waterproof tunnel in week 3. Backfill and pave tunnel in Week 4. Now make it continuous, so the trenching work is 10m ahead of the placing work, which is 10m ahead of the grouting work, which is 10m ahead of the backfilling. Add some staging areas and you have a 60m to 100m long section that is closed to traffic and it moves along at 10m per week. In old cut-and-cover, they did not have precast concrete, or fast hardening grouts - so this modernizes the old method. Station, now shallower, are decked over since they will take time - but now faster since not as deep.

[@wasmic5z]

10 m per week is awfully slow. That's just half a kilometer in an entire year. You would need to start work at multiple sites simultaneously if you wanted to use that method. TBMs can move at 20 to 30 meters per DAY.

[@walter2902]

@@wasmic5z The other beauty of cut-and-cover is that you can have multiple contractors working at same time. Also the operation is simple and conventional so all cities have multiple contractor who can do the work. With TBM, the entire thing must be finished before any station construction can start since the under construction tunnel must be used to remove the dirt.

[@wasmic5z]

@@walter2902 Here in Copenhagen at least, they're already building the stations while the tunnels are being drilled. Work on the stations continuous from the start of construction until the end - but the station just takes a lot longer to build than the tunnel does, so in the end the tunnel still gets finished first. Most of our metro is built with TBMs, but there are a few sections of cut and cover too. Obviously, both methods have their pros and cons... but in Copenhagen speficially, there are very few straight wide sections that are suitable for cut-and-cover.

[@ReallyNoAlex]

Super interesting video as someone going into studying construction management

[@ianweniger6620]

Thanks for the clarifier this morning!

[@neolithictransitrevolution427]

I think my big take away from the last few videos is express style services should almost always be TBMs, because they have few stops per distance and most of a TBMs costs are stations. If you want to have regular stops, you're more likely to want cut and cover.

[@laurencefraser]

Well, before you start taking the actual local situation into account, anyway.

[@jonw999999]

Seattle's North & University Link should have been this way... twice as many stations from Downtown to Northgate. Also they wouldn't be so deep and so reliant on always breaking down deep elevators and banks of escalators.

[@MarioFanGamer659]

And express services often take a more direct route compared to non-express services which take a less direct route. If it means to build a tunnel below buildings then you'd never want to use C&C there.

[@1978dkelly]

@@jonw999999 The huge gap between Capitol Hill and the University of Washington always looked weird to me.

[@JohnCroucherAU]

Cut and cover was done in Adelaide, Australia for a bus tunnel. All the people critical of the project referred to it as a “ditch with a lid”.

[@lachlanp4198]

I hate how Sydney metro and politicians uses deep stations as an advertising ploy, to convince people that deeper stations are more impressive and that it's some kind of engineering marvel, when in reality they're just inconvenient for anyone who actually uses the station.

[@dinoeiriksson3954]

Vienna's new Metro line, plus the extension of another, is build mostly with TBM, but they use C&C for the stations afaik.

[@Chiefgord3190]

I think TBM’s are very efficient, simply because the disturbance of above ground life is very very minimal. Cut and cover has its benefits for stations of course, but using that for a whole line would be inefficient, which is why it’s not utilized often. You must also factor in that most companies are penalized if they disrupt traffic (road closures, lane closures etc) so obviously cut and cover wouldn’t be a smart thing to utilize.

[@mrnoah53]

The majority of Brussels' metro system is actually build using the cut and cover system. Our newest line its new station is being built only using cut and cover.

[@mbwyatt1978]

Dumb question warning ☝️ In construction sites these days it seems things can come to a halt when there is so much as a fossilised feather or goldfish found... Does a boring machine just plow on with free reign? Is there a brontosaurus somewhere with a metro tunnel running right up its back passage? ... though that could be cool.

[@fallenshallrise]

I thought this too. I think that the likely hood of finding anything goes down exponentially the deeper you go. Because those TBMs dig so far down I wonder if they just don't run into anything except rock and dirt down there.

[@mbwyatt1978]

@@fallenshallrise thanks for your reply, I'm glad it wasn't just me 🙂 The reason I am curious is I am living in Melbourne, Australia and we recently have had Four boring machines tunnelling through our city. Two for a dual tunnel (ahem) "Metro" train line (which Reese has done an explained video), and another two as part of a Vehicle Freeway tunnel project (Westgate Tunnel). While yes they do reach significantly deep that is still four tunnels that have to rise in and out of ground level at some point using gradients sufficient enough for the job. So it just had me wondering, can we blast away the most preserved triceratops and never know it. Is it even a consideration. I am not banging on about conserving this and that... just genuinely curious.

[@RipCityBassWorks]

I prefer cut and cover and elevated to deep bore solely for the easier access to stations. Much quicker to walk down or up a flight of stairs or ramp than to take multiple escalators. Deep bore definitely has it's purpose though, especially for lines that don't cleanly follow roads.

[@davidlazarovich]

Definitely the preferred way to tunnel given the right conditions. I know the focus of this video was subways, but another pro of cut-and-cover is the added grade separation it can provide for existing passenger rail (commuter/intercity/regional) since it inherently makes the line safer and more efficient. The Middlebury Tunnel Project in Vermont was an excellent example of this. Previously, the line was trenched right through the center with two bridges so the "cut" was technically done so really what was left was the "cover". Now instead of a huge gap it has become additional green space in the center. If was planning transit upgrades and had to chose, I'd focus making passenger rail safer and more efficient than building new subway tunnels. But I'm also from VT where we only have Amtrak services

[@BillyBlaze6907]

Drinking game: Take a shot every time he says "cut and cover"

[@SteveBluescemi]

I wouldn't heap so much praise on the Canada Line. A big reason why they were able to do it faster and cheaper is that they simply cut corners by building smaller stations etc. They effectively pushed the costs of expansion into a vastly more expensive future. Using cut-and-cover definitely helped too, although the disruption to businesses caused so much outrage that the later Broadway line extension has been forced to use tunneling, despite being almost entirely underneath a straight, wide arterial street.

[@williamerazo3921]

Who cares about the disruption, they got paid for there disruption and got canada line built before the Olympics on time and on budget

[@plankton50]

Cut and cover might also be a way of making use of oversized roads in urban areas. You could use cut and cover as an excuse to replace car capacity with rail capacity, and then build the road on top better and more walkable in one project.

[@user-ct6vr8bq4b]

Well, Like you said, it depends on the environment and the buildings above. In tel aviv you can't use cut and cover beacause you have a whole city above. When they built the underground part of the "red line" in tel aviv (which is deleyed again) they used TBM for the whole part, its about 12 kilometers underground and it took them just a little over two years.

[@RMTransit]

The did Cut and Cover in Milan and Vancouver, there’s city’s above in these cases too!

[@williamerazo3921]

They did cut and cover in lower manhattan’s in 1910s when it was becoming the central business district at its time. Look how they built the 6ave line subway at 34st. That’s called disruption.

[@felipecabrera511]

In Santiago they’re using a mixture of construction methods to build the new Line 7. For a lot of the stations they’re actually using cut & cover since it’s cheap and it gives them the opportunity to improve a lot of the old infrastructure (like water & sewage pipes and electric lines); for the eastern half they’re using TBM for the tunnels while the western half is being tunneled with the more traditional NATM.

[@RealConstructor]

Cut-and-cover is possible but when the land is laying low in elevation, the concrete tubes are in groundwater and will float. In that case piling is necessary (piles with pull strength) to keep the concrete tube in its place.

[@K2teknik.]

Or you just freeze the surrounding around the concrete tubes, they have used this method here for decades. They also use freezing when digging into the ground in material that can be loose, freeze it and it is stable to work with, btw they freeze it for a long time like in more than a year. The construction method chosen depends on the circumstances, not all construction sites are the same.

[@TundeEszlari]

Amazing video.

[@ccudmore]

If you look at pictures from the 50s when they were building the Yonge and Bloor subway lines in Toronto, and see how disruptive Cut and Cover was, I don't think people would accept that level of disruption to their community these days.

[@1978dkelly]

Indeed, I would say that the disruption of cut-and-cover is one of the reasons we moved towards using bored tunnels. In the case of NYC, trying to do the large-scale cut-and-cover operations that gave them the subways to begin with would probably result in a flurry of lawsuits from business and property owners, community groups, and motorists claiming negative impact. Not that avoiding C and C solves this; bored tunnels are being used in Seattle and local residents still claim the disruption will "destroy their neighborhoods" and residents of Bel Air in Los Angeles object to a very deep bored tunnel under their neighborhood, mostly on principle (despite not having a station there or any real impact), but ostensibly that it would be a cave-in danger, somehow.

[@RMTransit]

I included pictures and discussed this in the video, we’ve improved these methods a lot in 70+ years! It’s not reasonable to compare how we did things in the 50’s imo

[@AndersonPEM]

Sheldon: Welcome to fun with trains. RMTransit: hold my coffee.

[@1978dkelly]

C and C is also less useful in places that don't have flat(ish) topography. It would have been very difficult if not impossible to build DC Metro's Red Line with cut-and-cover methods.

[@Skip6235]

I mean, Vancouver did it

[@1978dkelly]

@@Skip6235 Sorry, I don't know about the specific situation in Vancouver. In the case of Washington DC, a lot of it was done using cut and cover (at least the stations were), but the part of the Red Line on a steepish grade had to be done using a bored tunnel.

[@ethandanielburg6356]

I really appreciate the nuance in this video! It makes me wonder whether cut-and-cover stations (as opposed to mined stations) would have made sense as a cost-saving measure for the ridiculously expensive blue line extension in Montréal. Using a TBM to bore the tunnel probably makes sense given how narrow Jean-Talon street is, but maybe the stations could have been cut-and-cover boxes?

[@szurketaltos2693]

In China cut and cover stations are pretty common with TBM bored tunnels AFAIK. It's the best of both worlds really.

[@MarioFanGamer659]

Honestly, C&C stations should be the default unless local restrictons, lest because a hole has to be made for the TBM and all the excavation anyway.

[@szurketaltos2693]

@@MarioFanGamer659 question is, how do the costs compare? You may need to cut more than just an intersection depending on the size of said intersection, which would get into eminent domain. So like elevated and indeed cut and cover subway, cut and cover stations work best on stroads. Dream scenario is cut and cover a whole stroad and turn into a pedestrian street.

[@lzh4950]

Heard that Singapore announced the adoption of a technology where cut & cover (C&C) would initially be done a few meters deep, before the construction site is roofed over to allow vehicles to continue passing over the road cutting thru the site, & excavators would continue digging deeper beneath the roof (a bit like how Oxford Circus' Victoria Line's platforms were built for London's Tube). This technology was reportedly used to built Kaki Bt station but in the end the roofing was occupied by more consturction equipment, & the road cutting thru that area was still closed for almost 5 yrs as a result. Buses running along that road had to be diverted to a parallel road, increasing traffic jams there

[@Techno-Universal]

Cut and cover can also be extremely disruptive if the process involves digging up existing roads in major cities to build the train lines! Also elevated railway lines can also be a great solution for extremely long distance lines that run through areas that are prone to flooding or have significant populations of native wildlife while elevated lines have been progressively becoming cheaper to build over time with new techniques! :)

[@tylerdavidson2400]

Elevated lines are way cheaper and faster than underground. Thats why Asian countries like India are building them above ground.

[@tommywong3147]

We should get the team from Vancouver Canada line to build for Eglington.

[@earthsteward9]

I would like to see more cut and cover... except when the line crosses a river

[@AppleCheese12345678]

People have a really bad image of cut and cover. Even the Canada Line people hated at the time because it tore up so much of Cambie and downtown and was "disruptive". The Broadway extension was made specifically by tbm because of the uproar and pushback from the Canada lines construction.

[@fallenshallrise]

I always wondered if the fact that there is no station at 12th or 16th along Cambie is just revenge for those bushiness that worked so hard to try to block the construction that benefits thousands per day.

[@dashthecat0]

i thought the broadway ext is being made by cut and cover

[@AppleCheese12345678]

@@dashthecat0 only the stations

[@crismairo]

People talk about TBMs and Cut and Cover methods like they are the only methods of tunnel construction. Here at Santiago we became the MASTERS of NATM, there is a reason why we are building so much km of metro lines compared to the rest of Latin America (or America in general). We use Cut and Cover in small sections nowadays, because the construction of the oldest sections of Line 1 and 2 were too disruptive (but that doesn't mean that we abandoned Cut and Cover completely). For the new Line 7 we are using NATM and TBMs for the first time, but NATM is still the main thing.

[@cameronmorrison4502]

Yet another great vid on the channel ! You make a great point - Just because a given method or technology is old does not always mean it should be disregarded or thrown away. While new and better methods and technologies are certainly worth pursuing, the tried and true can still be the best solution.

[@MarioFanGamer659]

I think C&C benefits the most when a street has to be renewed as that way, two birds are hit with a single stone: A street periodically has to be repaved which means it will be closed to the street traffic altogether and C&C requires you to open up the street for the tunnels anyway. On the point of the fitting tools: I often talk about Frankfurt and once again, here it's relevant again: The underground section of the A Line, the north-south trunk, is mostly build cut & cover outside of the Sachsenhausen section which thanks to the Main must be mined (i.e. TBM), not dug out (clearly visible with the round tunnels at Schweizer Platz) as it mostly follows the existing streets unlike the B and C Lines and S-Bahn tunnels which have a high curvature and go below buildings much more often. In theory, a lot of the remaining overground sections of the network could be buried into the ground with C&C as they're using former tram tracks on four lane streets. In practice, some sections benefit more elevated guideways because the geography makes it difficult like the remaining Eschersheimer Landstraße section due to railway tracks and a river past Weißer Stein as well as everything north of it (which mostly consists of former railway tracks). Some others should rather be mined like the tram-like U5 since the Eckenheimer Landstraße it goes through is pretty narrow (incidently, it's also the reason why the U5 contains the only street-running section of the network) as well as the sharp curves at Marbachweg

[@DiederikCA]

Wow, i thought we had some expensive metro building in my hometown of Amsterdam. But it turns out thats just pretty average. 3 billion in the 2010s for a track that has mixed tunnel booring and cut & cover. But notably, in very marshy and archeological terrain, with expenses for foundational damage to historic buildings. So its actually better than people believe it to be

[@gymnasiast90]

The damage to the buildings on the Vijzelgracht was caused by the building of the Vijzelgracht station - which used cut-and-cover. The tunnel boring went without a hitch, including the bit where they slid a whole metro station under the Centraal Station, while the station remained open, and having to cut some of wooden foundation poles in the process. It really was a triumph of engineering.

[@takatomon]

I'm curious to understand how long/impactful the disruption would be and the time difference in comparison to a TBM. If there was sufficient zoning/planning done then C and C seems like a no brainer, however I feel like transit building has always been reactive and too little too late. By that point the density in the area you want to build too great, and the worry of re-positioning sewage, electricity and rebuilding of roads.

[@nbutler]

Would love to see this in more places than old cities. Even wild not as dense city like in Denver!

[@gurinderpurewal3689]

Regarding Cut and Cover and the Canada Line, you forgot to mention the massive financial impact that was burdened on the Cambie street businesses. A lot of small businesses were not able to cope with the disruption, and went our of business due to a significant drop in customers along the construction corridor.

[@walter2902]

Just as the businesses on Eglinton Ave. in Toronto went out of business due to the extremely deep cut-and-cover stations created from the TBM tunnels.

[@stickynorth]

Fun Fact about Edmonton's LRT system. It's used 3 different tunnel types depending on the soil conditions of the city. Cut & Cover for the simple section to connect to downtown in the NE which transformed into NATM for the riverbank portion near the Legislature which both sit on quicksand and have to extra reinforced before opening as well as TBM's for the steep section between University and Health Sciences/Jubilee at 6% grade where it ran under two hospitals and the busiest university in Alberta... And ironically enough NONE of these sections were over budget or delayed including the Valley Line. It's tunnel was built in only a few months with NATM again because of its riverbank location... The most problematic? The elevated guideway piers... 2/3's have had to be retrofitted because of premature cracking and spalling... And the line hasn't even opened...

[@ExecutorElassus]

A good example of doing cut-and-cover in stages while shifting the above-ground traffic around it is Stuttgart's tram stop at the southern and northern ends of their massive Hbf project. In both cases, traffic continued across temporary decks that were moved around as the crews dug out and built different parts of the stations underneath them.

[@themariokartlick]

I do have doubts that, at least in North America, cut and cover is that much cheaper. One, it requires more labor. That’s not really the main issue though. The main issue is that cut and cover sucks hardcore for people who will not live near a station but still experience all the disruption. In NA, those people tend to complain, sue, protest, and generally create problems. The method that is commonly used, TBM for the tunnels and cut and cover for stations is great because the people who are most affected are the people who receive most of the benefits. Not even to mention, the cost issues in NA can’t really be attributed to construction method, as in many other parts of the world (such as Germany, where I live), TBMs are mostly used for subways and things are still much cheaper. In fact in Germany a lot of rail construction in general today is tunneled and it is multiples cheaper than America (idk about canada though)

[@1978dkelly]

NA political culture (at least US & Canada) makes transit projects difficult in general. Some train lines which should be surface or elevated end in up tunnels (to appease NIMBYs), and some which should clearly be tunneled end up as surface lines (to appease budget hawks). Out of the scope of this video (a bit), but transit projects are often portrayed as stalking horses for "gentrification" and as having a negative disparate impact on different communities. Highly visible disruptions like cut-and-cover are often used as an example of this, but that doesn't get things like bored tunnels "off the hook" with transit opponents, either (bored tunnels can create their own types of disruption).

[@pbilk]

Reece, from your videos, you have made me a cut and cover fan. But I do understand when boring machines are ideal.

[@gymnasiast90]

To give an example where boring _does_ make sense: the Noord-Zuidlijn in Amsterdam would probably not have existed if TBMs were not an option. They used cut-and-cover for their first line (Oostlijn), which saw the demolition of a lot of buildings. They didn’t want this again, especially not as the Noord-Zuidlijn was going to go right through the historic centre with many narrow streets. Boring the tunnels went without a hitch, despite the Amsterdam soil having all the qualities of a plate of oatmeal. The infamous Vijzelgracht leak occurred on the station building site - which used cut-and-cover...

[@rockonileva]

Here in Curitiba, a mixed solution was planned to be used. The North/South line would be built below the existing BRT exclusive lanes. And through the city center, they would dig deeper until reaching the BRT lanes after. But it didn't happen and a we still rely only on busses on a city with 2million people.

[@Shiroupng]

pls do a video on the Buenos Aires suite

[@lawrencebautista1]

Korea seems to be doing it fast enough. Currently Seoul is building the Sinasan Line and they're not even using the traditional cut and cover method for the stations, minimizing obstruction at the surface.

[@lelandunruh7896]

I will admit that cut-and-cover makes life with a baby easier. Taking a stroller onto line M1 in Budapest is trivially easy compared to many stations in, say, Prague.

[@mglenadel]

in the 1970's, Rio de Janeiro used cut-and-cover for the first half of its subway system (originally called Line 1), and simple ground/elevated tracks for the other half (most of Line 2). Later on, to reach the South Side of the city (basically a thin strip of sandy soil squeezed between the ocean and granite mountains-the average width ranging from 200 to 300 meters), they had to dig through rock (although some parts of the path ran through a sand bar-Ipanema, as in "The Girl From Ipanema"-situated between the beach and a saltwater lagoon). It took a long time to finish, and it only happened at all because of the 2016 Olympics, with the influx of capital to get the city ready for the games. TBMs were not up for the task in most of the length, because of the hardness of the granite. Explosions, for years and years on end. I have an aunt who used to live near one of the job sites in Copacabana (right next to Ipanema) and she used to be terrified of the explosions, even though they set them at regular schedules and warned everybody in the neighborhood.

[@Ishantyagiofficial]

in ASIA most of the metro systems are elevated and if they are underground TBMs are used in India metro systems are largely elevated and if under ground sections are made up by TBMs

[@user-ck2ov9ff1o]

Cut and Cover is also way better for specific issues. For example, TBMs can't dig 3rd/4th tunnel behind the station for trains to turn around. Or to build a fork for trains to diverge to a different route (to the depot or different line section). TBMs also build only standard tunnels - you can't really do the double deck ones unless you make a TBM dedicated to this (very expensive). In Kyiv, there is a new extension under construction (prolonged since the start of COVID for various reasons) that utilizes both TBM (to cross a difficult terrain underneath a river and varying soils and awful lot of elevation) and cut&cover to build the other part that would have a double deck tunnel (it is there because the fork with 4 tunnels for a future branching section with a depot doesn't fit a narrow street). Using a single method wouldn't be optimal. Also: TBMs fare way better under the bodies of water, especially in long term. It doesn't have to be a river, stream or lake, but is also an issue with the underground rivers. C&C really struggles to provide same levels of isolation from water and disturbs soils too much as a result of intervention. That said, I really do appreciate cut&cover a lot.

[@HwanSangHyang]

Seoul Metro Line 1 (Opened at 1974) was built whole line in Cut-and-cover method) but It make very sharp curve too, especially between Cityhall - Jonggak. Gwangju Metro Line 2 (Now constructing) is Faster way to cut and cover. It use Pre made Module. and it can allow less time (but only at Straight Line) . By the way, construction is delayed by finantial problem. Busan Merto Line 1(Opened at 1986) was used Cut-and-cover method. but It can't be used at near Nampo Station. Because it is too close to sea, it was difficult to block water. Beacause of that, NATM was used at first time at south korea. (Nampo station opened at 1988)

[@nyc1164]

Cut and cover sounds practical but you also need to consider what to do with the sewer lines, gas lines and whatever else that runs underground. You have to reroute all of them.

[@booketoiles1600]

I think one reason that cut and cover costs can escalate is that ripping up the street is a good occasion to renew said street, like the cut and cover build of McGill station of the REM in mtl will be followed by ever more constrution on the street to make it into a very cool forested park. (Thankfully the park isn't paid by the REM's budget) In this case that's good, but in some cases it can lead to very long construction and tunnel budgets inflated by paying for car infrastructure above them

[@katrinabryce]

In the case of the DLR, there were no streets at the time the railway was built. It was a brand new district of London, they decided it needed transit if it was to be a success, and the railway and streets were built at the same time. When the Jubilee Line Extension came later, that was done using NATM, though their experience of that wasn't good and I don't think they will be repeating it.

[@Bobrogers99]

Relocating water lines, sewer lines, electrical lines, telephone lines, and internet lines under streets could be difficult because they are not always mapped accurately, and they are the property of many different agencies and companies.

[@walter2902]

Canada Line was mentioned. As far as I know (which is limited to Canada), that was the only project that truly gave the contractor the choice of construction method and they chose to put 25% of the 20km route as cut-and-cover instead of TBM. (The 25% under river and through downtown stayed as TBM.

[@user-ld4qx6sy2v]

I don’t have all the facts, but CRL in Auckland, NZ used the combination method. C&C was used mainly in the city centre is high still resulted in significant disruptions for several years. The negative public view and concerns for similar levels of disruptions and impacts on businesses was a key contributing factor for the light rail project to choose the boring technique when it chose the underground alignment -the underground alignment was also largely chosen to avoid disruptions both during construction and generally reallocation of road space!

[@Dqtube]

I'm surprised that's even a thing. After all, it's not common to use a combination of different techniques that are best suited to the location where the construction is taking place.

[@bonsaiboi9083]

It's the polar opposite of the way metros were built (and still are built sometimes) in the former soviet and eastern block countries. I live in Budapest and apart from M1 and some stations at the end of the other lines, you mostly go down a looong moving staircase befor you arrive a the platform. Line M2 and M3 were also built with military planning in mind, ie. for use as bomb shelters, also you can see huge steel doors that can be moved down to seal the stations during conflicts. I think it is not all bad to build deep, looking a Kyiv, you can see how important a deep metro can be. But still when I just walk down a set of around 20 stairs in Line M1, I see the perks of cut and cover :D

[@thevlogies2624]

Cut and Cover is currently being used in the construction of Phase 2 of Jakarta's MRT. They are still using TBM as well for the tunnels.

[@dr.eggmanrobotnik8684]

here in São Paulo, Brazil, a lot of metro projects are going on at the same time and, in the majority of them (Except the monorail projects) the cut and cover technique is being use for stations, while the tunel boringe machines are being used for the tunels, because of the extreme dense areas where the line are being construct or expanded

[@IamTheHolypumpkin]

My city pioneered the “new Austrian tunneling method in urban areas”. On the lines U4 and U5 of the Frankfurt U-Bahn the method was used on the section half way between the Stations Willi-Brand-Platz and Dom/Römer and Dom/Römer and Konstablerwache where build this way. The Station Dom/Römer was build Cut and Cover. The tracks there underpin multiple centuries old building. Some listed. Including a huge Church (the Dom) and our City Hall (Römer). Even an archaeological dig site from the Rome empire.

[@MarioFanGamer659]

It's actually interesting D/R is C&C since it's located right below some buildings which is untypical because they'd be demolished to make way for the station (one of the station entrances is even located inside one of the buildings). OTOH, the old city had to be reconstructed anyway so there were no buildings in way.

[@walter2902]

The reason there is no cut-and-cover is the delivery model. If the entire project is awarded to one contractor, then they can find efficiencies and a more expensive tunnel (cut-and-cover) may be worthwhile since the stations all become cheaper. The other end of the spectrum it to break the design up into a number of small pieces, to allow maximum number of contractors to work on it - increasing speed and having competitive prices. Cut-and-cover is great for this as multiple contractors can begin immediately at multiple locations. What does Toronto do - a TBM contract and a massive stations contract. TBM can't be optimized as it goes where it has to go. Work on stations can't begin until TBM is finished, making construction take longer. Only few contractors can bid on huge stations contract, so higher prices. The perfect "worst of both worlds" situation.

[@GoderichBoy]

I’m a civil engineer and I like your channel. Let me give you my experience as I’ve been in the room when construction method decisions are made on major transit projects. Key reasons why cut and cover isn’t employed as much A.) Politics at all levels. Cut and cover is incredibly disruptive. The impact on local traffic and traffic for small businesses makes it so unpopular that no politician/municipal official wants to advocate for it. Public uproar costs votes. 2.) Utilities, Utilities, Utilities. Most people have no clue the tangled web of gas mains, old rickety water mains, FOC, power cabling that exists underground. The design/relocation costs are astronomical. Don’t get me started on schedule…if you think current schedules are bad, wait until you have to relocate a large gas main or 2. 3.) adjacent structure settlement. No one wants to take the risks of causing settlement to adjacent buildings or bridges or other critical structures and being sued. I could go on and on…my suggestions for improving transit construction schedules? a) Take a hard look at permitting processes. There are months/years that could be shaved off schedules if we could avoid the layers of bureaucracy. b) Keep building! Canada hasnt been consistent in building subways/rail infrastructure. The local subcontractors that are the backbone of any project had to relearn and up their capabilities…building is a skill. You don’t use it, you lose it. There are so many more things i could add here but most people are probably not reading this far so I’ll stop now…😂. Let me know if you’d like to talk more about this topic. This is literally my job.

[@RMTransit]

Yes, but cities, all around the world have masses of utilities Underground, and from what I’ve seen Canadian cities are actually pretty good!

[@GoderichBoy]

@@RMTransit Underground utilities are not unique to Canada but the processes involved in this country are probably very unique. We do bureaucracy very well. As I said, it’s not just utilities. Cut and cover to any constructor just screams risk, risk, risk and construction costs would balloon even if you could get past the political hurdles. I’ve been involved on the sharp end of the last decade of subways construction in Toronto. It really isn’t that simple. Again, love your channel. Keep those videos coming.

[@RMTransit]

I have lots of thoughts but, I just see “Canada has unique processes and bureaucracy…” as being a bad reason. I get things are bad here, but they are bad in a lot of places! Anyways thanks for sharing your insights!

[@walter2902]

If stations are 150m long, and they are spaced at 800m, then 20% of the route is cut-and-cover anyway - and you have to figure out the utilities for a reasonable percentage of the route anyway. It won't help reduce station costs to make the tunnel/station half as deep? Also, can't pre-cast box tunnel be used to reduce disruption time. As far as I know, Canada Line was the only location where contractor was given a choice, and they chose half the underground portion as cut-and-cover.

[@matsv201]

As an actual civil engineer i think this is way to simplistic. Firstly when it comes between underground, on ground or over ground, this is not the decision of engineers (generally) but to city planers (that typically are architects, not engineers, but well they can be what ever). When the decision is made to do a underground part its the engineers turn.. people like me.. When selecting method... well there is more than just boring and cutncover, there is also cover (with out cut), trenching, blasting, freeze and cut and, build and cut .. really a bunch of other method. Firstly we have to check how deep the tunnel need to go, and can go. There are of cause geometric restriction, while subways can go pretty steep that is typically less of a problem than for heavy rail. So in a lot of cases, there is not even a option between boring and cutncover. In a lot of cases its just a matter of geometry. But lets say the situation is ideal. Say for example the rail tunnel in Malmö where the depth was just right to do either cut and cover or boring machine. And that was exactly the case there. Either method was fine well at least of a part. Then its about economics. And you might think, well cut and cover will always be cheaper... wrong. It depends. what is on the surface, and what is just under the surface. Pipes, cables, fiber. In a city like malmö (and really at least most major nordic cities) in the urban core there is typically 2 or 3 fiber network. surface water pipes, waste water pipes (and those can´t mix) clean water pipes (and those can´t certainly not mix), 2 heat water pipe (flow and return flow) and also in some places 2 chill water pipes and power of cause. Most of them have to be rerouted.l And most of them have to do so with out losing function during the build period. So you have to first dig up the street, make new pipes and cables before cuting of a single cable over the trench. During this period a section along the edge of the trench have to be open. While part of it can be covered by temporary bridges, this disturb the traffic. And for ground water and waste water it get worse. Those can´t flow uphill. And you can bet that one side of the trench will be uphill in all direction. Then you need a pump station (or several). Those need to have a pump tank, backup generator and... loads of stuff. All that have to be finished before the cut even start. And the more infrastructure there is in the ground, the harder it is. This is one reason this is harder today than 150 years ago. They had no internet, no district heating, certainly no district cooling and very seldomly even fresh water. In most cases there was pretty much just waste water. So if you have a TBM you don´t have to care about all that.. well.. sort of. But you need to care about other things. TBM works great in soft rock and other semi hard ground condition. They work sort of okay in soft ground condition. and they can work in hard rock as well. The issue is that you need diffrent heads for different condition and you might slide from one condition to a other, making it harder. There are multi heads, but those also have limitations (and they are expensive). On the other hand, TBM can be very cost effective if ground-condition is just right. Back to Malmö. A railway tunnel need to be built from one side of the city to the other. The cut was semi deep. so both CutnCover and tunneling was fine. There was plenty of park areas to dig in and the ground condition, while not good, (very soft clay) was on the other hand, very uniform. The tunnel was built between 2005 and 2010, so in reasonable recent times. So what method did they choice. Both. Well. actually 3 different method. Starting from the old station the new station was build in a cut. This area of town was quite industrial and there was space to move traffic around. Also, building a station with cutncover is way cheaper. From there the tunnel was built in cutncover under a park and a few roads close to the park. In the south end of the cut was two TBM installed side by side. They would race the rest of the way.. well almost. But.. well that was not the end of it. A bit south still was a other station, Triangel station. That was built via a cut. Because.. well boring a station is really hard, and expensive. So the TBM would drill right into the wall of the station. But, that of cause mandated that the wall of the station was built before the TBM reach it. This is actually a quite common method. The two TBM run right throw the station, and keep drilling on the other side. going south to the edge of town where it went out to a half cut. This part of the city have been reserved for something like 20 years to be a cover for the railway line A new city part was built on top of part of the rail line, that at this end was pretty much totaly over ground. This city part started building in 2008... well not a great timing. This what suppose to be the best address in the city, with 6 minute rail to Denmark. is still to this day not even haft finished. (well a significant part of the rest of the area is a construction zone today, so it might be finished with in the next decade) Every engineer working with this know the pro and cons. I´m not even working directly with tunnels. just working with making the general line, but i do need to know the restrictions and cost. I can´t just say, do cutncover, its the cheapest.. because it might not be. You absolutely can go under buildings. Its not even that hard.There are photos from a south american build where they cut out a building totally and its pretty much hovering in mid air (with support). Cut and cover is not really that much faster. It really depends on the scale of the project. For something like a long tunnel with no station, a bored tunnel have virtually no disruption. The main problem is the stations. You have to have space to do the work. And you can´t really use the tunnel, because generally the station must be built prior. In stockholm the stations was bult via secondary entry shaft. This was quite efficent and pretty much all work took place practically 100% under ground

[@RMTransit]

Of course, there are other construction methods, but this is a video about cut and cover! The whole point of the video was not to blindly suggest one construction method is better than another !

[@matsv201]

@@RMTransit My main argument was not really that we should choice one or the other, but in actuall reality, there is often a quite clear best solution The people doing the actual detail tunnel planing have very little leverage to choice one or the other. Its really geography and cityscape that dictate the choice. Even in a place like malmö, there was a quite clear distinction from two fairly similar part of the city

[@RMTransit]

I don’t agree, in North America (and to an extent beyond) the decision is frequently political. There are often multiple possible technical solutions and in many places these decisions are not made based on which is best alone. I’m not sure if you’ve followed projects like the San Jose BART extension but, projects such as that are a perfect example of a solution being used that is clearly not technically best, but which is politically popular. I’m ultimately also not really interested in placing blame on one particular party, which is why I don’t talk about those details in the video, but there are clearly a lot of wide flat streets in North America that do not need to be tunneled bored under - the overall outcome is my concern.

[@matsv201]

@@RMTransit Well if you go for the track layout, that is a quasi political decision. If its going to go overground or underground is effectively a political decision. "clearly not technically best, but which is politically popular. " I have not followed the project, barley know it exits. I have seen that statement for many different project, but its quite often not the case. With that, it does happen once and a while. It does happen. Typically when the political pressure is very high. But its not always that easy to tell. It not always do to popular demand. There was one example close to home where it was pushed really hard with a railway tunnel throw a ridge, and the policymakers didn´t understand the tunnel was 150 meter under water. The ridge was soked and there was large cracks all the way

[@RMTransit]

I’m simply responding to the idea that it’s “way too simplistic” these things truly are often made at a political level, and I think that’s bad!

[@collectivelyimprovingtrans2460]

Can't help but think that cut and cover is a great way to build new subways all around the world. Thinking of NYC subway lines that have to be underground and built easily.

[@ninnobroggi]

Can you do a video on Frankfurt am Main's Subways?

[@ccudmore]

Cut and Cover definitely doesn't fit well with crossing rivers!

[@groundzero_-lm4md]

Subways are usual built under roadways. So having a bridge with a roadway on the top deck and a subway bridge below would work.

[@ethandanielburg6356]

Many cities have built subways using cut-and-cover to dig underground and submerged caissons to build tunnels underwater.

[@RMTransit]

Immersed tube is sort of like cut and cover

[@alexmccutcheon7381]

I still remember wandering around the streets of Paris and being acutely aware of which metro lines were built as cut and cover...because you could clearly hear the trains as they passed just a floor or two below street level. Not sure if this is the case everywhere, and it's certainly quieter than an overhead rattler, but it's definitely a consideration that counts against the cost savings.

[@Thomasmuller2309]

If you are interested you could inform yourself about the extension of the U5 of the Frankfurt Stadtbahn-system. A short amount of it is cut with tunnel boring machines, but the rest is just done in a typical light rail style without a tunnel with street crossings. In my opinion this would have been a perfect space to use the cut and cover method, especially because the street is wide enough for people still to drive during construction work. But they dont do it and when the project is finished there will be slow and unreliable services.

[@ulysseslee9541]

the fastest way: change the old and useless but near a crowed area/office place railway to a metro line track & extend the route from it.

[@johnchastain7890]

Seems to me the main determinant of the subway construction method is geology. My hometown, Washington DC, had to operate two entirely different sets of construction equipment to build the underground portions of the Metro. Why? Because the east coast fall line runs right through the city. Above the fall line: rock tunneling. Below the fall line: cut-and-cover. Also, running under various bodies of water (Potomac and Anacostia Rivers; Rock Creek, which is in a deep gorge right in the middle of the city) required very deep rock tunnels and stations, even though most routes ran under city streets. ***Bonus subway fun fact! During construction of a tunnel that ran very close to the Potomac (and thus below sea level), the DC Metro once froze the world's largest ice cube to keep the tunnel from flooding. This was confirmed by observers from the Guinness Book.

[@quoniam426]

Paris metro has some cut and cover sections, every flat roof station is basically cut and cover, quite many stations on Lines 1, 2; 3, 4 and 5 (the first lines of the network so the most shallow), more rarely on lines 8 and 9 (the latter swtiches to metallic girders to art deco reinforced concrete masonery). More recent stations built in suburbs sinces the 70s were mostly built in cut and cover, lines 5, 7, 10, 13 (line 1 at La Défense is ab exceptions, it in fact reuses an already built highway tunnel to decrease costs). More recently, despite mostly using TBMs, nearly all recent stations were built in the modern Cut&Cover method, a box for the stations and a TBM going through them. The only use of old fashioned Cut&Cover method was for Line 4's extension last stop, Lucie Aubrac, the tunnel is right under the street, the station exit peaks out to the surface with windows enlighting the station, the garage tunnel after the station was completely dug from the top to bottom and covered up. By contrast, the station just before, Barbara is much deeper and vaulted as is Mairie de Montrouge because of lots of abandoned quarries that had to be bypassed. Fun fact, Porte d'Olréans (line 4 former terminus until 2013) is the shallowest Paris metro station, at least on its Northern extremity where stairs were added to allow an easier transfer with some bus lines, there is only ONE stair volley to access the street and NO corridor between the two platforms, Budapest Line 1 style ! On the Grand Paris Express, except for three stations (St Maur Créteil, Vert de Maisons and extremities of Villejuif Gustave Roussy), line 15 stations are all built with the Box+TBM method except for the Eastern terminus, Noisy-Champs where the station is the shallowest at -15 m only, the garage tunnel is completely built in Cut and Cover. The other exception is Pont de Sèvres which is built boldly into the River Seine quay directly ! (the only place where they actually put it close to Line 9 terminus and ensure a somewhat nice transfer (not optimal but the Pont de Sèvres bridge foundations don't allow for many other options) Gustave Roussy is a very special case, a 70m diameter well, 55m deep ! Lines 16 and 17 underground stations are all built with the Box+TBM method except for the above ground viaduct parts of Line 17 near Villepinte and the trench terminus envisaged North East of the CDG airport. Lines 14, 15, 16&17 transfer station at St Denis is a gigantic rectangular bow which features the lines going parallel to eachother and a set of transfer floor over, inside the box. Line 18 is built the same way, one station will be added later on at the interface between the underground section Eastbound and the viaduct at Palaiseau, a 100 m flat section is reserved to add a station aside the tracks when needed. (a last minute modification which is well deserved). The Massy-Palaiseau station on the other end will be a well covered in a glass roof in the middle of the train station and freight tracks, connecting to the two ped bridges linking RERs B and C and TGV station already. Lyon metro was mostly built around this principle, with the exception of the last Line B extensions that were built the modern way, station box+TBM.

[@KyrilPG]

I'm pretty sure the Northern hub of the GPE, Saint Denis Pleyel, wasn't built with box + TBM but with the TBM + box method. That's sounds like the same thing but it's actually the other way around : tunnel first, box later. I've seen pictures and videos where they dig around the recently built tunnel and "unbuild" it when they reach the right depth. And in the case of this hub station, they also reversed the order of "cut-and-cover" for the station box and used mostly "cover-and-dig", and repeated the operation for every level. There are other stations in the same case but I don't remember exactly which ones. One station in Paris that has quite a unique and remarkable building method is the new la Defense station for RER E that is due to open later this year : it was built like a mole, from under the massive CNIT triangular building, creating new reinforced and much deeper foundations while the building functioned normally above. Plus, the station is pretty cathedral-esque, with a massive mezzanine above the platform, forming a huge void under the somewhat historical structure of the CNIT expo center. Weren't the new extension and stations on the North end of M12 built with a TBM and box method? From what I heard, RATP and its contractors used the cut-and-cover method on line M4's South extension with a hefty dose of regrets at certain locations. It apparently was due to the horrendous cost, delays and complexity of utility realignment, the famously hollow Swiss cheese that is the shallow Parisian underground, riddled with quarries and gypsum layers, and the systematic vicinity of some very loosely defined aquifers. Anyway, building a subway line in Paris is always quite challenging, not to say nightmarish, whatever the chosen method. They had to freeze the ground on the last phase of the M14's North extension tunnel, near the hub if I recall correctly. It was due to the rather bad location of the mandatory emergency exit & ventilation shaft, if memory serves. They also endured a surprise flooding, but I can't remember which line extension it happened on. They also had many similar issues when building M12's North extension. And bam ! Several years of delay and a nice big cost overrun but now it's open. There aren't many infos yet but from what I gathered, the East and West parts of M15 will use a selection of different methods to build the stations, so as not to encounter the same issues in a seemingly more complicated and less welcoming terrain than the M15 South section. Saint Cloud station will be one (of several) to watch for, as I doubt they'll use the common box technique there. As for M1 Eastern extension, they may have to resort to a different technique than the initially planned cut-and-cover method for the Vincennes underground junction. Local opposition and environmental concerns (tree cutting) have ballooned and probably contributed to tip the scale on the negative judgment of public utility. There are also important concerns about the massive underground junction in Rosny.

[@unlapras9365]

Yes, Paris still mostly builds its stations using C&C but not tunnels. Stations are vaulted only when it is technically impossible to dig a trench above the tunnel, like on line 14 between Saint-Lazare and Châtelet due to the line being built below apartement blocks.

[@quoniam426]

@@KyrilPG Yes there are two methods for box and TBM, the Top to Bottom (digging from the ground to the bottom of the trench) and the Bottom-Up, (digging like mole from the lower levels up to the street level. Line 12 had to resort to freezing around Aimé Césaire station extremities near the Ourq canal because the ground was not stable enough but they messed up with the usual salt water method and resorted to EXPERIMENT on liquid nitrogen instead, starting again TWICE because they messed up the first time (three attempts with the two methods combined) leading to a severe delay (4 years + 1 year due to Covid restrictions. Line 14 had to freeze terrain under RER C tunnel in St Ouen, it was one of the last pieces of tunnel made for the St Ouen extension and it went pretty quickly. The delay was due to flooding in Porte de Clichy station box because... all of the water that the new tribunal's foundations displaced. That wasn't accounted for until it was too late because the metro building works began with a delay letting the tribunal being built first when it was supposed to be built after the metro. The delay was due to decontamination of the St Ouen terrains where the new line train maintenance depot is while it used to be an oil refinery, Total not wanting to clean their mess when RATP bought the terrain had to settle the issue in court (Paris Administrative Court) which decided that BOTH companies should work hand in hand for the site's decontamination since none of them wanted to take charge...) leading to two or three years delay. Part of Line 12 extension delay was also due to Veolia Sewage department not willing to actually MOVE the sewers prior to the construction work as it is traditionnally done. St Cloud will be built in a hill, the terrain there has some severe slopes and cliffs for an urbanized area One example of stations built with the TBM going through first was Châtelet on Line 14, that's why its ceiling his higher than the others because they were building it while the TBM was passing just under the work site ! Line 4 construction in Bagneux actually damaged nearby condo buildings because of excessive vibrations, leading to works stopping to stabilize the said buildings. Anyway, the place will have a big metamophosis, new buildings being built at once with the GPE station anyway... Rosny Line 11 terminus was very simple to build, just under the shopping center car park on the other side of the RER station, however, they changed the plans for the line new train depot and workshop several times before settling on the definitive place and access tunnel supposed to be before the station, along the tunnel to Paris before being settled after the station, leading a possible connection to the future extension to Noisy, if it is ever built, that is (local politicians seem to recently want to ressurect the shelved project). Geology is ine thing, political shenanigans are as nightmarish as geology in Paris (and not just Paris, London or New York had their fair shares of those as well...) Noisy didn't want the T1 tram to be extended through the city center because it would take too much space and damage the shops's clients visit potential... so the tram will make a detour on the outskirts to serve future neighbourhoods instead. Same in Colombes, future Western T1 extensions will avoid a small avenue because the Fire Brigade department was unwilling to change their procedures for the tram overhead wires and local residents didn't want to share the road with the tram, so it will make a detour North via the outskirts and future neighbourhoods as well... At least it could serve the interests of a possible GPE extention on Line 16/17 to Nanterre with a station in Colombes to be really efficient, fast and complementary to the tram. Not every shenanigan will lead to a nightmare, some can have benefits...

[@barryrobbins7694]

Thank you so much! Societies, for the lack of a better word, need to have longterm vision to thrive. Mass transit system construction methods are a very important subset of a subset of a subset, etc. In everything regarding mass transit, or any human endeavor for that matter, we should keep the vision in mind, but adapt as necessary. Myopic self interest seems to be a major obstacle to good mass transit in North America - and in other matters too!

[@theusov]

Quite random comment: I've watched one of your shorts talking about shallow subway stations and I'd like to talk about Praça Onze station in Rio de Janeiro's Line 1 I think this is one of the only underground subway stations where the whole station mezzanine is in ground level and you can see the sky from the train platform, since it was made with cut and cover and it is pretty shallow

[@baystated]

Some cities who got trenches cut are still waiting for the covers, both for transit and roadways. Either developers don't want urban air rights or transport agencies or governments won't price them to sell.

[@yegfreethinker]

Cut and cover is the best. People just need to suck it up. Mild inconvenience for huge gain