The United States Has Too Few Road Tunnels
The Francis Scott Key Bridge in Baltimore collapsed after a drifting freighter hit one of its supports; so far, six people are presumed dead. Immediately after the disaster, people were asking if it could be prevented, and it became clear that it is not possible to build a bridge anchor that can withstand the impact of a modern ship, even at low speed. However, it was then pointed out to me on Mastodon that it’s not normal in Europe to have such a bridge over a shipping channel; instead, roads go in tunnel. I started looking, and got to a place that connects my interest in construction costs with that of cross-cultural learning. Europe has far more road tunneling than the US does, thanks to the lower construction costs here; it also has better harmonization of regulations of what can go in tunnels and what cannot. The bridge collapse is a corner case of where the American system fails – it’s a once in several decades event – but it does showcase deep problems with building infrastructure.
Road tunnels
The United States has very little road tunneling for its size. This list has a lot of dead links and out of date numbers, but in the US, the FHWA has a current database in which the tunnels sum to 220 km. Germany had 150 km in 1999, and has tendered about 170 km of new tunnel since 2000 of which only 48 are still under construction. France has 238 km of road tunnel; the two longest and the 10th longest, totaling 28 km, cross the Alpine border with Italy, but even excluding those, 210 is almost as much as the US on one fifth the population. Italy of course has more tunneling, as can be expected from its topography, but France (ex-borders) and Germany are not more mountainous than the US, do not have fjords and skerries like Norway, and don’t even have rias like Chesapeake Bay and the Lower Hudson. Japan, with its mountainous island geography, has around 5,000 km of road tunnel.
The United States builds so few tunnels that it’s hard to create any large database of American road tunnels and their costs. Moreover, it has even fewer urban road tunnels, and the few it does have, like the Big Dig and more recently the Alaskan Way Viaduct replacement tunnel, have become bywords for extreme costs, creating distaste even among pro-highway urban politicians for more and leading to project cancellations. With that in mind, the State Route 99 tunnel replacing the Alaskan Way Viaduct is 3 km long and cost $2.15 billion in 2009-19, which is $2.77 billion in 2023 dollars and $920 million/km, with just four lanes, two in each direction.
In Europe, this is not at all an exhaustive database; it represents where I’ve lived and what I’ve studied, but these are all complex urban tunnels in dense environments:
- Stockholm: the six-lane Förbifart Stockholm project to build long bypass roads in Stockholm using congestion pricing money, after acrimonious political debates over how to allocate the money between roads and public transport, comprises 17 km of tunnel (plus 4 km above-ground) including underwater segments, for an updated cost of 51.5 billion kronor in 2021 prices, or $6.97 billion in 2023 PPPs, or $410 million/km. The project is well underway and its current cost represents a large overrun over the original estimate.
- Paris: the four-lane A86 ring road was completed in 2011 with 15.5 km of new tunnel, including 10 in a duplex tunnel, at a cost of 2.2 billion €. I’ve seen sources saying that the cost applies only to the duplex section, but the EIB claims 1.7 billion € for the duplex. Physical construction was done 2005-7; deflating from 2006 prices, this is $4.18 billion in 2023 PPPs, or $270 million/km. This is a tunnel with atypically restricted clearances – commercial vehicles are entirely banned, as are vehicles running on compressed natural gas, due to fire concerns after the Mont-Blanc Tunnel fire.
- Berlin: the four-lane 2.4 km long Tunnel Tiergarten Spreebogen (TTS) project was dug 2002-4, for 390 million €, or $790 million in 2023 PPPs and $330 million/km. This tunnel goes under the river and under the contemporarily built Berlin Hauptbahnhof urban renewal but also under a park. The controversial A100 17th segment plan comprises 4.1 km of which 2.7 are to be in tunnel, officially for 800 million € but that estimate is out of date and a rougher but more current estimate is 1 billion €. The exchange rate value of the euro today belies how much stronger it is in PPP terms: this is $1.45 billion, or $537 million/km if we assume the above-ground section is free, somewhat less if we cost it too. The 17th segment tunnel is, I believe, to have six lanes; the under-construction 16th segment has six lanes.
Crossing shipping channels
The busiest container ports in Europe are, by far, Rotterdam, Antwerp, and Hamburg, in this order. Rotterdam and Antwerp do not, as far as I’ve been able to tell from Google Earth tourism, have any road bridge over the shipping channels. Hamburg has one, the Köhlbrandbrücke (anchored on land, not water), on the way to one of the container berths, and some movable bridges like the Kattwykbrücke on the way to other berths – and there are plans to replace this with a new crossing, by bridge, with higher clearance below, with a tunnel elsewhere on the route. The next tranche of European ports are generally coastal – Le Havre, Bremerhaven, Valencia, Algeciras, Piraeus, Constanța – so it is not surprising the shipping channels are bridge-free; but Rotterdam, Antwerp, and Hamburg, are all on rivers, crossed by tunnel.
American ports usually have bridges over shipping channels, even when they are next to the ocean, as at the Ports of Los Angeles and Long Beach. This is not universal – crossings in Hampton Roads have tunnels – but it’s the trend. Of note, the US does occasionally tunnel under deep channels (again, Hampton Roads); that the Netherlands tunnels in Rotterdam is especially remarkable given how Holland is a floodplain with very difficult tunnel construction in alluvial soil.
Hazardous material regulations
Tunnels do not permit all traffic, due to fire risk. For example, the Mont-Blanc Tunnel requires vehicles heavier than 3.5 tons to undergo a safety inspection before entering to ensure they don’t carry prohibited dangerous goods. In Europe, this is governed by the ADR; all European countries are party to it, even ones not in the EU, and so are some non-European ones. Tunnels can be classified locally between A (no restrictions) and E (most restrictive).
The United States is not party to the ADR. It has its own set of regulations for transportation of hazardous materials (hazmat), with different classifications – and those differ by state. Here are the rules in Maryland. They’re restrictive enough that significant road freight had to use the Key Bridge, because the alternative routes have tunnels that it is banned from entering. Port Authority has different rules, permitting certain hazmat through the Lincoln Tunnel with an official escort. Somehow, the rules are not uniform in the United States even though it is a country and Europe is not; Russia and Ukraine may be at war with each other, but they have the same transportation of dangerous goods regulations.
Pedestrian Observations 
Ditto for railroad tunnels. The longest railroads tunnels in North America today were exclusively built between late 19th and early 20th centuries, in sharp contradiction to situations in Eurasia countries, which generally saw constructions of record-setting railroad tunnels in the second half of the 20th century as the tunnel-boring technology advanced.
Actually, the longest railway tunnel in North America, the 14.7 km Mount Macdonald tunnel under Rogers Pass in British Columbia, was built in the 1980s, partially with a tunnel boring machine. https://en.wikipedia.org/wiki/Mount_Macdonald_Tunnel
The problem with the Key Bridge was the lack of sufficient concrete “dolphins” to protect the bridge piers from a strike by a wayward ship, it had four in the four quadrants around the bridge, but they where located pretty far from the bridge piers and didn’t cover the angle that the containership came in on, its possible it sideswiped one, but I think it missed it.
In contrast the new Sunshine Skyway Bridge over Tampa Bay built in the 1980s which replaced the one partially collapsed after a collision with a freighter lost in a fog, as multiple dolphins plus stone riprap around the piers. A local news station from Philadelphia did a aerial inspection of bridges over the Delaware River and found them much better protected than the Key Bridge, the local bridge authority in an interview stressing the proactive steps taken over the years to protect their local bridges. Other local TV news stations inspecting local bridges found them much better protected as well with bumpers, wood pilings, riprap islands and weirs, and concrete dolphins.
The likely replacement of the Key Bridge will be a new cable sway span, as they is now the bridge type of choice for spans over broad navigable waterways, as seen with numerous new bridges in America over the past four decades, including the new Sunshine Skyway Bridge, new Tappan Zee Bridge, Copper River ‘Arthur Ravenel Jr. Bridge’ in Charleston, new Corpus Christi Harbor Bridge, several bridges over the Houston Ship Canal.
The likely cable sway replacement bridge in Baltimore will have a wider span over the shipping channel, its main piers for the towers will be protected by artificial islands of riprap, and then their will likely be a lot of concrete dolphins. Given the racism of Francis Scott Key (he was a slave owner who made several unsavory comments on African-Americans, but as a lawyer also did represent slaves seeking a legal recourse to being freed and enforced wills freeing slaves, making efforts to ensure that the former slaves were self-sufficient) the new bridge might not be named after him, but the Star-Spangled Banner most certainly will be played at the opening day ceremony.
I’ve actually driven through one of the Baltimore tunnels 😀
Tangential:
This was the consensus I saw reached by non-engineers on Twitter and Mastodon, and by some civil but not structural engineers on Reddit. Clearly, though, this is false in the literal interpretation (specifically: a sufficiently strong pier is close enough to ‘impossible’, but you’d add protection around the pier). One real-world example that was found, rated for 120,000 tons at 7 kt (80′ dia dolphins for two piers, project cost $93 M). That’s on the same order of magnitude as the Dali. Even without doing any calculations, 5 m of concrete or riprap wouldn’t stop the Dali, 500 m would, then use the intermediate value theorem. You just have a big-ish cost escalation for a very low probability, high severity event*. The social media consensus in this case was just parroting of early take-havers, as far as I can tell.
*It’s possible a normal benefit-cost here for the bridge rebuild wouldn’t recommend pier protection rated high enough to prevent a repeat of the Dali collision (I think between $12 M per fatality and economic impacts, it probably makes sense), but I’m sure they’ll design for somewhere around there regardless due to optics.
5 m of concrete or riprap wouldn’t stop the Dali,
Actually, 5m of concrete or rip rap almost certainly would stop a ship the size of the Dali, if it projected above the waterline. Ships that size run aground on mud all of the time, so that much mass of stone and concrete would bring the ship to a halt. The engineering issue at that point is having enough standoff distance from the barrier to the pier so that the force of the impact isn’t transferred to the bridge regardless (a situation of the-ship-hits-the-barrier-then-the-barrier-hits-the-bridge).
a normal benefit-cost here for the bridge rebuild wouldn’t recommend pier protection rated high enough to prevent a repeat of the Dali collision
After the Sunshine Skyway Bridge in Florida collapsed after a ship strike in 1980, AASHTO updated its standards to require fenders or dolphins to protect bridges from this kind of accident, so even if the Key Bridge were not being rebuilt due to failure, any replacement would have pier protection as a matter of course, not because of optics.
Also at $12M per fatality, this accident is already at $72M before economic impacts so clearly the cost-benefit would argue for, not against, pier protection. Especially since this was a minimum case fatality event, if the work crew had not been on the bridge the quick thinking to stop traffic in response to the Mayday would have meant zero fatalities. The Sunshine Skyway Bridge collapse in the middle of the day resulted in 35 deaths, or $420M of impact, which makes the ~$95M pier protection cost a bargain. If the collision on the Key Bridge had happened at rush hour, the deaths could have been hundreds and thus the cost of protection becomes negligible in the face of the potential impact, even if the probability is very low.
even if the probability is very low.
Upon reflection, with this disaster bringing to light 4 ship/bridge incidents in the past 44 years, maybe they actually are not that uncommon.
[summary] Mild dissent on the magnitude of some values. I agree on what should be done (add adequate protection on all new-build bridges; retrofit existing bridges with protection where it makes sense), I just don’t think some of your “x is certainly/clearly y” claims are obvious without some consideration and calculation. My conservative calculations show (1) it’s not “almost certain[]” 5 m of riprap/concrete would stop a vessel like the Dali, (2) it does seem “clear[ that] the cost-benefit would argue for” protection.
[width of protection necessary to stop a ship] This one is very tangential/irrelevant since the 5 m value was just something I chose at random, sorry! But I checked, so may as well keep this in. Skip if you want.
It’s not obvious to me that a ship would stop in 5 m, given ships are far from rigid, so I checked AASHTO’s bridge design standards. I don’t do bridge design, or anything structural, so any misuse of the methodology or miscalculations are mine alone. If you want to verify, you can find the 4th edition PDF on Google, they’re on 9th ed. now but I don’t do structural work so no access. I don’t imagine the equations have changed that much though.
The only real-life example with good pictures I could find (it’s surprisingly hard to find how far ships are penetrated in collisions for individual cases) looks like around 4 m? I found the particular incident from the second-last link in this comment, pdf p. 16. I would guess the velocity of a bow of a ship turning in a terminal is at speeds lower than the 8 kt = 15 kmh of the Dali, but I’m not sure especially since it was turning. Here’s a video of a container ship turning in the same port as that collision (Oakland), your guess of bow velocity is as good as mine.
(3.14.7-1) gives kinetic energy with some adjustments, I get KE = 1,737,754,200 J using NYT’s estimate of “195,000 metric tons fully loaded”. AASHTO calls for displacement tonnage which Wikipedia gives as 148,000 t. (3.14.8-1) models “head-on ship collision impact force on a pier” as Ps = 1.2*10^5 V sqrt(DWT) = 169003103 N for us. (3.14.9) gives “bow damage length of ship” (m) as 1.54 * (KE / Ps) = 16 m. This assumes rigidity of the static object.
Now (1) these are engineering design standards, with multiple factors of safety built in to the equations, so the Dali certainly may have stopped within 5 m; (2) since riprap requires a slope, the effective width in this case will be ~2x larger given the shape of ship bows (dolphins appear to have a basically vertical profile though); and (3) AASHTO doesn’t provide any engineering details about dolphins, fenders, abutments with riprap etc. other than briefly mentioning they’re possible collision countermeasures, these equations aren’t intended for their design as far as I can tell.
While I can believe 5 m would be sufficient to stop such a vessel, I just don’t think it’s obvious that it is. Anyways, this was intended against people on social media who claimed, probably from a game of structural design telephone, that bridge protection was literally impossible from an engineering perspective. That sentence in my original post just meant to convey [some small amount of protection is insufficient, some large amount is sufficient, therefore there does exist some minimal amount of protection that stops ship-bridge collisions]. 5 m is close enough to the design value I get that it’s certainly possible.
For reference: on the Skyway bridge’s main piers, there are about 33 m of above-high water riprap before any concrete in the longitudinal direction and about 12 m in the lateral direction.
[benefit/cost analysis and collision probability] New AASHTO standards: good point, didn’t know this. Design standards for structures like this are much stricter than the often politically-influenced road design process (in the US) I’m more familiar with. From a national perspective, return period of ship-bridge collapse of 11 years is indeed common, but benefit/cost analyses are from the individual structure perspective, which makes that once every some hundreds of years.
Anyways, this point was again just something where the relative magnitudes aren’t clear to me. Of course if we can expect one collision with a particular bridge with a probability anywhere north of ~10% in its lifetime, protection makes sense, but it’s distributed among the many bridges near many major ports.
We want, for protection a given bridge to make sense, cost(protection) < P(collision in design life) * cost(collision impacts).
Here cost(protection) is maybe $50 M on the low end, probably lower for smaller bridges (about zero for bridges with piers on land, like in Los Angeles). cost(collision impacts) is maybe 50 fatalities * $12 M, plus economic impacts: CNN says 1 month to clear, so let’s say 2, Al Jazeera says economic impacts around $15 M/d, we’ll make this $30 M to be conservative and also to account for economic losses after the channel is cleared due to shifting traffic patterns. This gives a design cost(collision impacts) of $2.4 B, which means we must have P(collision in design life) > 2%. Is that the case? I’m not sure, maybe!
To accurately calculate P(collision in design life), we’d want to account for exposure weighted by ship tonnage, bridge design characteristics, weather conditions by region, etc. That’s too hard, so the AASHTO specs and this document give a simplified methodology for calculating P(annual collision). That’s also too hard, I don’t have enough data to estimate the annual probability of collapse. If you want to try, I got a probability of abberancy (for an individual ship) conservatively 0.00019 and annual vessel traffic around 1,000, but we need more terms to calculate (3.14.5-1). So instead we’ll inaccurately estimate it as ([# collisions in observation period]*[design life])/([duration of observation period]*[number of bridges in class]). You say [#collisions]=4, [duration obs period]=44, and we can say [design life]=50 which is fairly standard.
CBS claims the National Bridge Inventory has “4,207 bridges in the U.S. that allow ships to pass under them, according to the National Bridge Inventory. Of those, only 36% are described as having functional pier protection — and that included the Key Bridge”. Like lots of federal data, there are separate files for each state and no combined file for all of them, so I won’t verify this. Anyways, it seems way too high for bridges comparable to the Key Bridge. Let’s say there’s 50 comparable bridges in the US. Then we get P(collision in design life) = 9%.
So, under some conservative assumptions (half-cost protection, double duration of incident cleanup and double daily econ impacts, high fatality incident, but I think these are within range of some 90th-99th percentile event probably) it definitely makes sense to protect any given new-build bridge (for adding protection to existing bridges, value needs to be scaled by [total lifespan/remaining lifespan]). But these are on the same order of magnitude, it was not obvious to me before checking whether this pencils in terms of a simple benefit/cost analysis.
It’s such a ridiculuous thing that Brightline West is designed with that many sharp (R<2000m) curves (hence speed restrictions below 200kph) generally not seen on new 300-kph high speed lines elsewhere in the world, only to minimize bridge and tunnel structures in uninhabited deserts.
https://railroads.dot.gov/sites/fra.dot.gov/files/fra_net/3576/Appendix_F_C_Plan_and_Profiles.pdf#page=11
https://railroads.dot.gov/sites/fra.dot.gov/files/2023-07/Attachment%20F_Footprint%20Drawings.pdf
Oof. That alignment is nuts! Any other country wouldn’t bat an eye at drilling an (at most) 10 km tunnel through Cajon Pass. And for some reason it hugs I-15 the whole way — even right through Barstow — without there even being a stop planned there. What madness!
Check out the track grades in that first document! (160mb PDF warning) OMFG!
2.5% is kind of down there at the low end of what’s allowed. 3.5% is nothing to mention, really. Oh you want 4.5%? Got you covered on that. In mass quantities.
The whole things is … rather interesting.
Train braking requirements are going to be quite something.
All with bonus roller-coaster alley-oops over each freeway interchange. Whee!
Following a freeway is a common refrain in the US when it comes to rail infrastructure buildout attempts like this. About $3 billion USD is coming from the US DOT, while the remaining estimated $9 billion USD (kek! 🤣) will have to be privately sourced, so it’s understandable that they’re trying to minimize construction and land acquisition costs (as getting an easement for the I-15 corridor is probably substantially cheaper). But it does go to illustrate just how difficult it is to build anything decent in the US within reasonable costs… 😞
As I understand it, the United States Navy pushes for tunnels in the Hampton Roads region so that saboteurs (or accidents) can’t isolate Naval Station Norfolk from the Atlantic by bringing down a bridge. I guess that kind of pressure makes money less of an object.
Yes, and this is also why the Brooklyn-Battery Tunnel is not a bridge – the feds had concerns over enemy action destroying a bridge blocking access to the Navy Yard, and Moses took it as a personal slight at how dare someone else impose any constraint on him.
There are many myths surrounding Robert Moses. The same enemy could have destroyed the Brooklyn Bridge or the Manhattan Bridge. Or the Williamsburg or the Queensboro. You can’t go upriver from Hampton Roads to get to the ocean but you can from northern Brooklyn.
I think part of it is cultural. Robert Moses is the genesis of a lot of highway planning, and the planners under him were also influential, and he famously did not like tunnels; the only tunnel he ever built was the Brooklyn-Battery Tunnel, which was only a tunnel because President FDR himself intervened.
That being said this is just kind of a risk with bridges in general. For example the bridge linking Kansai International Airport to the rest of Japan got struck by a tanker in 2018. https://en.wikipedia.org/wiki/Sky_Gate_Bridge_R
it is not possible to build a bridge anchor that can withstand the impact of a modern ship
This is not true, as with any engineering problem there is a solution to resist a given force. The Bay Bridge to San Francisco has been struck by large oil tankers twice in the past 20 years with no damage to the bridge. The Golden Gate Bridge has an enormous concrete ring surrounding the south tower than goes down to bedrock 34m below the water (as with the Chesapeake Bay Bridge and the Brooklyn-Battery Tunnel, the US Navy had significant influence on the design of the Golden Gate Bridge regarding height etc. to maintain access to what was then a major naval port). The problem is that the Key Bridge didn’t have such a fender to protect its towers.
Stating that the Köhlbrandbrücke is anchored on land not water is disingenuous, the Köhlbrandbrücke spans just 320m of water, the Key Bridge was over water for 1600m+, and that would 2500m+ if not for the causeway at the east end.
I don’t see how anything to do with Mont-Blanc would have helped in Baltimore by building a tunnel instead of the Key Bridge. Your link seems to indicate that vehicles over 3.5 tons are inspected to ensure they meet emissions standards, not because the inspection allows the tunnel to carry goods that would otherwise go by open road. Mont-Blanc is ADR E and doesn’t allow hazardous goods, if Baltimore’s other two tunnels are the same then there could still be seen to be a need for a bridge across the harbor.
I -695 is a beltway. The hazardous goods can use the counter-clockwise roadway through the northwestern suburbs. No one will be happy about it but they can.
Good point.
As a local, yes they can and should. Some will try to use local streets (especially those just going from one side of the harbor to the other, e.g. Dundalk to Curtis Bay)-there’s been some commentary abt trucks switching to the Hanover Street Bridge, which is only accessible via neighborhood streets unless you go through the Fort McHenry Tunnel, which hazmats aren’t allowed to do. So I expect complaints abt big rigs and hazmats trying to cut through neighborhoods soon. Only certain city streets allow big trucks, so we’ll see.
And to be fair in the 1999 Mont Blanc tunnel fire 39 people died. That’s a lot worse than this bridge.
So for the Hampton Roads Tunnel and the Thimble Shoal tunnel the bored tunnels have to be designed for ship impact, despite being bored tunnels below the sea bed…..weird but true.
According to an article excerpt on reddit, the initial plan was for a tunnel.
Oregon and Washington plan to replace the I-5 bridge over the Columbia River and add light rail and a cycling lane. To avoid a drawbridge section like the current one, it will have to be quite high and steep which can get dangerous in sometimes challenging Pacific NW. Some people have suggested an immersed tunnel, but thus far the transport departments have pushed back. I hope this accident will make them reconsider as Bob Ortblad on X: “Baltimore has two immersed tunnels and in 1970 it planned a third tunnel, but the collapsed Francis Scott Key Bridge was built. An immersed tunnel can be built faster and with less maritime disruption than a new bridge. @USCGPacificNW @PortlandCorps @IbrProgram https://t.co/GtmGrKwNyn” / X (twitter.com) points out.
You also forgot to mention Hamburg’s New Elbtunnel, which is under the main shipping lane
I looked at it while blogging and decided against putting it in the bullet points because it opened 1974 so it’s not the best cost comparison.
There is a price estimate for the bridge replacement now: https://www.ndr.de/nachrichten/hamburg/Neue-Koehlbrandbruecke-soll-bis-zu-53-Milliarden-Euro-kosten,koehlbrandbruecke384.html
Just like eliminating rail level crossing is an improvement work for road not rail, I think eliminating road bridge on shipping channel is an improvement work for harbour nor road.
It all seems to come down to money. And the fact that Baltimore is not a big naval base–because the navy would have insisted on a longer span and much more fortified piers. Like they insisted with the south pier of the GG bridge in San Francisco, which was a major naval base and of course subject to fogs. The GG south pier is the only one in water and is massive and involved a huge cofferdam for construction all of which added quite a bit to the overall cost, ie. compared to before the DoD modifications. And that was exactly 40 years earlier than the FS Keys bridge (1977).
When they got the bids for building the Keys bridge all were beyond the budget so they forced a lower price on a local contractor and cut other corners; eg. it was built as 4-lane but the approaches were built as 2-lane and years went by until they could fund their upgrade to 4. Looking at the pics (before the accident) the piers look seriously minimalist. The official commentary has been that they were built to then-standards but could not cope with modern day monsters like the Dali Panamax, however it really doesn’t look like it would have survived a lot smaller ships. I suppose there could be more extensive piers underwater but that footage of the accident seems to suggest WYSIWYG from the pictures of the pre-collision bridge.
The other factor is that it is a truss bridge and close to the limit for that type, 366m versus 400m for the world’s largest. Again this is probably on cost grounds compared to a suspension bridge with a much bigger central span (the reason for choosing a suspension design). My guess is if they rebuild a bridge (and I’m guessing they will) it will be cable-stayed using the piers at the end of the secondary arch of the old bridge to give a central span of 600m to 800m. Cable-stayed are very popular because they are the most efficient structure on cost, simplicity of construction, strength and construction time, and of course they look good.
I can’t speak to the specifics of the Key Bridge, but despite what many people are saying even a strong enough pier (instead of just fender/dolphin protection around it as discussed above) isn’t impossible. In the Sunshine Skyway collapse referenced above, the main piers actually withstood the impact, it was when the short storm below the ship into the secondary piers that the collapse occurred. The main piers, being next to the channel, were engineered for a ship strike (I think? They may have just been stronger because they supported the main span) but the secondary piers were not. For the new bridge the protection plan of course extends several hundred meters to either side of the shipping channel, covering many sets of piers.
there are nothing that aren’t about money.
You forgot the whole Baltic Sea, which is connected through Öresund and the Great Belt, both which have bridges. The main reason is that the Danish sand is very difficult terrain for tunneling.
The Gothenburg port is also partially behind a bridge, Älvsborgsbron, though the main container port is on its outer side, and mostly Ropax ferries go under it.
The Öresund Bridge is partly a tunnel…
In both cases there is insufficient depth to get a large ship anywhere close to the long bridges for either the Storebaelt or Oresund crossings. Storebaelts suspension bridge foundations are well outside of the marine channel and most of the heavy traffic goes through Storebaelt due to the very deep channel that is available compared to Oresund.
And the ground is not that difficult, look at all the successful Metro tunneling in Copenhagen. The tunnel under Storebaelt was very difficult for many reasons but lessons learned would make the tunneling alot more straightforward using modern TBM’s compared to what was available at the time.
The Öresund Bridge is partly a tunnel…
And yet the super-large cruise ships built at Turku in Finland need folding stacks to squeeze under the Great Belt Bridge. Why don’t they just use the Oresund? This is a legitimate question, I don’t understand why they have to go to lengths like folding tunnels and scheduling transit at low tide when the Oresund has unlimited air draft. If there is a reason that major shipping has to use the Great Belt instead then @elmoallen has a point about Baltic access being bridge limited.
I can only imagine its a water depth issue. With Oresund being an immersed tube tunnel you cant really dredge the channel to increase the draft. It is what it is.
But the bigger question is why do cruise ships have to be so large???
You might want to look back into the Storebaelt history, during construction I seem to recall there was a court case between Denmark and Finland about the bridge height, that the Danes lost. But as its 30 odd years ago I don’t really remember the details.
The reason cruise ships are so tall is that the other two dimensions are more restricted, so economies of scale go in this direction.
Length (whichever definition) is limited by ship handling in port and other restricted waters. Beam is not actually the dimension of interest, but superstructure width. Cabins with a natural view are worth significantly more than cabins without one, thus — assuming a fixed internal volume for a sec — a taller, thinner superstructure is better than a squatter one. Furthermore, height is not particularly restricted by marine architecture concerns in a way it is for other types of ships. Most importantly, the bulk density of a metal-structure hotel is much, much lower than the bulk density of other kinds of cargoes. This means both that buoyancy is satisfied with a shallow draft, and in turn that shallow draft (relative to beam) gives plenty of stability (“metacentric height”) to play with. (For a fixed angle of list, the shallower draft-to-beam ratio means that the line through which the buoyancy force acts moves farther to the side, i.e. acts on a longer arm i.e. exerts more torque. The point where for small angles the line of the buoyant force intersects the symmetry line of the ship is called the metacenter; for stability purposes, the ship can be treated as if it were suspended by this point. Their shallow draft makes cruise ships so stable that many put a swimming pool, full of heavy water (…no, not D2O) on the top deck. It turns out, you don’t want to the center of mass to be too far below the metacenter, because then the ship will rock side to side too fast and your passengers will get seasick.)
So I did some digging and apparently the Oresund has just a 7m minimum depth at its limiting point, which is very shallow for major ocean going ships (the St. Lawrence Seaway, basically an inland river, offers 8m, and the original Panama Canal draft was 12m, now 18m). The Great Belt is apparently 14-15m, which is exceeded by oil tankers and the very largest container ships, but not much else.
I checked and the lawsuit between Finland and Denmark was exactly over the height of the Great Belt Bridge and closing the Baltic to ships taller than 65m. However, it was Finland that lost when the International Court of Justice refused to issue an injunction stopping construction, at which point Finland and Denmark settled out of court for $15M to Finland but the bridge built as planned.
The fact that the entire Baltic Sea has had its main shipping channel permanently restricted by a bridge sort of torpedoes Alon’s argument that Europe takes pains to build tunnels not bridges across important shipping channels.
An exaggeration. The only ships blocked by the Storebaelt are those absurdly tall cruise ships and they have the simple solution of folding stacks. The only other things blocked are oil-rigs heading to the North Sea. Clearly this is why Denmark won the court case. 65m clearance is plenty.
What struck me about the Storebaelt is the cost: €2.8bn. For Denmark’s biggest infrastructure project. I’ll bet rebuilding the Keys bridge will cost more, probably a lot more. For a lot less.
[I’ve actually done that crossing back in the day (1980s) on the night-train to Copenhagen in which the train is rolled onto the ferry.]
But what about the Bosphorus and the Hellespont some of the busiest marine passages in the world and in a country with (today) an efficient tunnel sector. Only three tunnels to my knowledge cross the Bosphorus, the Avrasya Tunnel (Road-TBM), Marmaray (Rail – immersed tube) and the Melen water tunnel (TBM). And there are 4 road bridges between the two channels, 3 across the Bosphorus and 1 at the Hellespont. Here though its geography that plays its part with the main pylons close to or on land and the main span able to cross the passage.
So there are many reasons to choose one or the other and the first inclination is always a bridge due to its lower costs and the fact it looks nice…… what I am seeing in the market is governments and transportation planners becoming increasingly concerned about the reliability of an above ground network in terms of safety and security even before this incident. Will that trend mean more tunnels are built, who knows. But as a minimum I would assume some of the more critical infrastructure elements that piggyback on bridges may well get relocated to dedicated crossings….
I’m hardly an advocate of car-centric urban construction, but even aside from the examples you give it’s hard not to notice the *lack* of subterranean infrastructure in general, not just the near-absence of tunneled urban freeway ring roads and bypasses and the like. For example, underground parking (sometimes it feels like there’s one under every city square in Italy and much of Germany) is also scarce in most of the US. Cheap land, urban cores raped by surface car storage, surface freeways and “redevelopment”, bad decades-retro construction culture and practies, it all adds up. Cheaper to knock down some poor people’s homes and bulldoze the surface roads through and build the above-ground parking. There’s just no incentive to learn to dig better.
Yeah, and residential parking too. Here, regrettably, new buildings have underground parking garages, even in Mitte, even right on top of train stations. (If there’s not enough room for cars then the Greens will have won and that’s worse than terrorism if you ask Axel-Springer media.) Do new condos in the US do that? I was under the impression they preferred above-ground parking podiums, or maybe parking in what here would be the courtyard?
Depends on where in the US. In Texas the “Texas Donut” is common, which is a condo building wrapped around a multi-story parking garage instead of a courtyard
In slightly denser places it is common to build 3+1, 4+1, 4+2 (also described as ‘three over one, four over one,…’) which is one or two stories of concrete columns and deck, followed by the remaining building framed in wood or light gauge metal – in those cases the ground floor (or perhaps the ground floor and all/part of the 2nd) are given over to parking. This model is also sometimes seen in smaller motel style garden apartments, where the first floor is just an open carport with the first occupied floor sitting on columns above (common in warm climates where there will also be no hallways, just outdoor walkways to the rooms).
In dense areas able to support high rises then there will be underground parking, since there usually has to be excavation for foundations anyway. Often times part of the first one or two floors will also be parking depending on the size of the building. It remains to be seen during the next boom cycle if this trend continues in cities that have worked to eliminate parking minimums in the past few years. Before COVID parking stackers were becoming common in the most urban areas (SF, NY, Bos) to about halve the parking space needed and maximize the number of units.
In most places in the US parking for condos/apartments is just a lot next to or behind the building. Land is plentiful and cheap in suburbs and newer sunbelt cities, so there is no real penalty to doubling the lot size necessary for a building by including surface parking, just as most stores have a large parking lot in front of them.
Tunnels have risk too. It is interesting that almost all tunnel disasters are outside of the US. Notably,
– Mont Blanc Tunnel (France/Italy)
– St. Gotthard Tunnel (Switzerland)
– Tauern Tunnel (Austria)
– Channel Tunnel (Eurotunnel) (France/UK)
– Kitzsteinhorn Tunnel (Austria)
– Hallandsås Tunnel (Sweden)
– Hsuehshan Tunnel (Taiwan). Besides disasters, there are many accidents in tunnels too. Who can forget Lady Di?
The Pennsylvania Turnpike is preparing to close one of its tunnels and replace it with a cut. An engineer quoted in a news report on that project said something like, well, tunnels are relics of the past. If you built a new turnpike today, you’d never build tunnels.
It seems that tunnels are a design solution that’s mainly used in the US when you’re trying to make land available on the surface for something else. For example, in Kentucky, a tunnel was built under Cumberland Gap in the 1990s to remove traffic from a historical park; more aristocratically, a few years later on the opposite end of the state, a tunnel was built on a ring road extension to preserve a listed heritage estate. See also Route 99 in Seattle and the Big Dig, which were intended to free up surface land for development.
I think that highway officials in the US tend to oppose tunnels in most other situations partly because they are more complicated to operate and partly because of the hazmat restrictions, but mainly for a planning reason: tunnels are much harder to add extra lanes to than a road cut or even a bridge.
Given the “one more lane” philosophy of highway planning that’s so dominant in the US, it’s very important for officials to preserve the option of widening the road in the future without having to dig a whole new tunnel. Cautionary tales of early highways that filled up with traffic much sooner than expected with no provision for expansion are taken seriously.