Great overview of construction methods and associated direct and indirect costs. Only very few companies make modern TBMs and usually they are not moved from one city to another but made for a specific job and partly assembled on site. This adds cost. The article doesn’t speak about the cut and cover hole needed to launch or retrieve the TBM. It also doesn’t mention how Musk’s Boring company’s TBM achieves a higher rate of speed than conventional TBM’s, albeit so far only for smaller tunnel sections not useable for subway, LRT or trains.
Brian, that was a great post. Both the history and the social effectors that drive design were nuggets of information that certainly backfilled my understanding of the transit and tunneling.
When the MASS dig project opened, you could feel the collective sigh for those driving in the area. Thank you.
The difference between elevated trains and cut and cover is that whole cut and cover has become more disruptive, elevated trains have become muc less so (modern elevated trains are quieter than an average two lane urban highway, and require less large structures). There's a reason countries that actually build metros build a lot of elevated lines (but rarely use cut and cover for tunnels anymore).
Vancouver’s current Broadway Line extension of its LRT line (Skytrain: though much of the total is actually elevated electric trains on concrete supports, the Canada Line, as the article says, and the new Broadway Line, have significant portions sub-surface ) is a combination of cut-and-cover and TBM, even though the cut-and-cover is along a major transportation and shopping route, Broadway. It has caused conflict, from affected businesses, commuters and residents, but presumably not enough to outweigh the advantages. It makes for a great viewing experience for those interested in the project :-)
As a traveller, I have noticed one of the advantages of the NY subway line is it is “right there.” You walk two short flights of stairs from street level and you are on the platform. Other cities usually require going down a flight of stairs and then riding down a massive 4-6 story escalator. This human experience is a legacy of cut-and-cover.
The newest stations and lines in New York City (on the 2nd Avenue line) are annoying because they require that massive escalator descent. They weren’t built just under the street.
One disadvantage is that it is not uncommon for the New York City system to get flooded during massive rainstorms. I don’t know if that happens as much elsewhere.
Another disadvantage is wxisti ny infrastructure. Cut and cover was also first implemented before the ground under the city streets was infiltrated with telecommunications, utility, water, and sewage lines
This article should mention the civil engineering downsides.
The one project shown as cut-&-cover was not. Ottawa’s LRT Line 1 thru the downtown core (which opened in 2019) used a pair of TBMs to bore 2.5km of tunnel & 3 underground stations.
However the Stage 2 extension of Line 1, which is currently being built & scheduled to open in 2026, *is* using cut-&-cover for part of the western extension along the Ottawa River and under a portion of Richmond Rd and Byron Linear Park.
Great piece and discussion of cut and cover. To add further detail for the Docklands Light Railway (DLR), a lot of the line utilised existing railway infrastructure that was no longer in use to save on costs. Hence it ended up above ground.
Cut-and-cover can happen in Detroit. The streets here are wide and unused. There are 10 lane roads in this city that could realistically be cut to 0 lanes with significantly impacting travel times, so overbuilt is the city’s auto infrastructure.
It is the perfect candidate for cut-and-cover. I have talked about writing such an article for about 3 years now and have some drafts. Perhaps I will now.
Yours is a fallacious line of thought. A city does not grow in linear, predictable steps, but as an act of self-creation distributed across its every resident, business, and institution, each of them in dialogue with one another and themselves. The creation of the rail line does not happen independent of density, or density independent of the rail line, or any part of the city from any other part—or from the national or international or historical context, for that matter.
So, the question is not, “is there _currently_ enough demand upon this unimproved corridor to sustain a rail line?”, but,” once built, will there be sufficient demand along this corridor to support the rail line?” In other words, is building our city in this way _a good investment_?
A rail line supports more walkable neighborhoods which drives retail revenue. Surges in retail revenue create jobs and attract residents. The ability to forgo cars for those along the line, especially if the line is integrated into a wider system, means they are able to drive additional money into the local economy. The density creates more customers, entrepreneurs, employees—an entire ecosystem. And density itself creates economic value by bringing Americans of different walks of life, professional and cultural background into close contact with each other. This is one of many well-known “agglomeration effects”, different efficiencies and self-reinforcing feedback loops that explain why dense neighborhoods are more productive than less dense neighborhoods—in other words, why cities form at all.
The usage of an automobile traffic study to determine whether a train should be built—which is exactly what your comment suggests—takes stock of none of this complexity. To be honest, your reply exemplifies the exact unimaginative and myopic thinking that has held American cities back for the better part of a century now.
But when you say no one is using the street or that it wouldn’t affect traffic, it makes me think you’re building in a wasteland or at least a very low density area. And sure, I’m all about the idea of transit-oriented development and upzoning and even transit-first greenfield cities, if we can get the political will.
People build cities. A subway system will not simply fall out of the sky upon hitting a certain density. The best time to build is _before_ the density is there.
It’s not so much the constriction of the tunnel sections where cut and cover is best - it’s for the station. The huge mined stations used for the new line in NYC is a major culprit of the excessive cost.
Great overview of construction methods and associated direct and indirect costs. Only very few companies make modern TBMs and usually they are not moved from one city to another but made for a specific job and partly assembled on site. This adds cost. The article doesn’t speak about the cut and cover hole needed to launch or retrieve the TBM. It also doesn’t mention how Musk’s Boring company’s TBM achieves a higher rate of speed than conventional TBM’s, albeit so far only for smaller tunnel sections not useable for subway, LRT or trains.
Brian, that was a great post. Both the history and the social effectors that drive design were nuggets of information that certainly backfilled my understanding of the transit and tunneling.
When the MASS dig project opened, you could feel the collective sigh for those driving in the area. Thank you.
Fascinating article!
One typo: "unlike an elevated train, that disruption remained after construction was complete"
(should be "unlike a subway")
The difference between elevated trains and cut and cover is that whole cut and cover has become more disruptive, elevated trains have become muc less so (modern elevated trains are quieter than an average two lane urban highway, and require less large structures). There's a reason countries that actually build metros build a lot of elevated lines (but rarely use cut and cover for tunnels anymore).
Vancouver’s current Broadway Line extension of its LRT line (Skytrain: though much of the total is actually elevated electric trains on concrete supports, the Canada Line, as the article says, and the new Broadway Line, have significant portions sub-surface ) is a combination of cut-and-cover and TBM, even though the cut-and-cover is along a major transportation and shopping route, Broadway. It has caused conflict, from affected businesses, commuters and residents, but presumably not enough to outweigh the advantages. It makes for a great viewing experience for those interested in the project :-)
As a traveller, I have noticed one of the advantages of the NY subway line is it is “right there.” You walk two short flights of stairs from street level and you are on the platform. Other cities usually require going down a flight of stairs and then riding down a massive 4-6 story escalator. This human experience is a legacy of cut-and-cover.
The newest stations and lines in New York City (on the 2nd Avenue line) are annoying because they require that massive escalator descent. They weren’t built just under the street.
One disadvantage is that it is not uncommon for the New York City system to get flooded during massive rainstorms. I don’t know if that happens as much elsewhere.
Another disadvantage is wxisti ny infrastructure. Cut and cover was also first implemented before the ground under the city streets was infiltrated with telecommunications, utility, water, and sewage lines
This article should mention the civil engineering downsides.
The one project shown as cut-&-cover was not. Ottawa’s LRT Line 1 thru the downtown core (which opened in 2019) used a pair of TBMs to bore 2.5km of tunnel & 3 underground stations.
However the Stage 2 extension of Line 1, which is currently being built & scheduled to open in 2026, *is* using cut-&-cover for part of the western extension along the Ottawa River and under a portion of Richmond Rd and Byron Linear Park.
https://en.wikipedia.org/wiki/Line_1_(O-Train)?wprov=sfti1#Stage_2
Yes! Thank you! We have to go back to cut and cover. Ideally with corvee labor. Been saying this for years.
Great piece and discussion of cut and cover. To add further detail for the Docklands Light Railway (DLR), a lot of the line utilised existing railway infrastructure that was no longer in use to save on costs. Hence it ended up above ground.
Thank you very much for this extensive overview! I learned a lot.
Cut-and-cover can happen in Detroit. The streets here are wide and unused. There are 10 lane roads in this city that could realistically be cut to 0 lanes with significantly impacting travel times, so overbuilt is the city’s auto infrastructure.
It is the perfect candidate for cut-and-cover. I have talked about writing such an article for about 3 years now and have some drafts. Perhaps I will now.
If no one is using the street, is it densely populated enough to warrant a rail line? (Unless it’s driverless, of course)
Yours is a fallacious line of thought. A city does not grow in linear, predictable steps, but as an act of self-creation distributed across its every resident, business, and institution, each of them in dialogue with one another and themselves. The creation of the rail line does not happen independent of density, or density independent of the rail line, or any part of the city from any other part—or from the national or international or historical context, for that matter.
So, the question is not, “is there _currently_ enough demand upon this unimproved corridor to sustain a rail line?”, but,” once built, will there be sufficient demand along this corridor to support the rail line?” In other words, is building our city in this way _a good investment_?
A rail line supports more walkable neighborhoods which drives retail revenue. Surges in retail revenue create jobs and attract residents. The ability to forgo cars for those along the line, especially if the line is integrated into a wider system, means they are able to drive additional money into the local economy. The density creates more customers, entrepreneurs, employees—an entire ecosystem. And density itself creates economic value by bringing Americans of different walks of life, professional and cultural background into close contact with each other. This is one of many well-known “agglomeration effects”, different efficiencies and self-reinforcing feedback loops that explain why dense neighborhoods are more productive than less dense neighborhoods—in other words, why cities form at all.
The usage of an automobile traffic study to determine whether a train should be built—which is exactly what your comment suggests—takes stock of none of this complexity. To be honest, your reply exemplifies the exact unimaginative and myopic thinking that has held American cities back for the better part of a century now.
But when you say no one is using the street or that it wouldn’t affect traffic, it makes me think you’re building in a wasteland or at least a very low density area. And sure, I’m all about the idea of transit-oriented development and upzoning and even transit-first greenfield cities, if we can get the political will.
Amazing you are still 100% missing the point. Here is the subway being built out into Queens. Literal farms.
https://i.insider.com/5bef271c0591f24c42109b2e?width=700&format=jpeg&auto=webp
People build cities. A subway system will not simply fall out of the sky upon hitting a certain density. The best time to build is _before_ the density is there.
It’s not so much the constriction of the tunnel sections where cut and cover is best - it’s for the station. The huge mined stations used for the new line in NYC is a major culprit of the excessive cost.