>> "... you could spend those same billions to build higher capacity transit."
Former tunnel boring engineer here.
This is true, but the real elegant solution is to build everything closer together by an order of magnitude, thereby raising the number of destinations in an N minute walking radius and eliminating the need for tunnels. If your urban design depends on cars-in-tunnels, it's a "code smell" that you've made a grievous system-scale architectural error.
We should keep building cities the way people did for thousands of years, with mostly little 10-foot wide (building-face-to-building-face) streets and a very few larger boulevards. This is how Venice works. This is how Tokyo works. This is how lower Manhattan works, and it's awesome.
LA's streets are probably ~100 ft between building facades, on average, so we could infill a bunch of little narrow streets of buildings in each one, raising destinations-per-acre by ~an order of magnitude or maybe more.
This destroys demand for transit by inspiring a modal shift to pedestrianism, and now you have a much smaller problem to solve. You can take all the tax revenue from the new buildings in your newly-densified city, and the money you saved on paving/traffic lights/street upkeep, and use it to build a real 12-trains-per-hour, quad-tracked, express-and-local service, 24 hour subway. Elon's Boring company can dig the tunnels for these if you want.
If you have money leftover you can build through-core commuter rail, that comes from the northern suburbs and goes through downtown out the other side to the southern suburbs, with a one-seat ride. If you still have money leftover you can give it to the homeless or something; under no circumstances should anyone ever spend money on putting cars in tunnels, which is one of the all time dumbest ideas and a prodigiously ugly solution to a prodigiously ugly problem.
> We should keep building cities the way people did for thousands of years, with mostly little 10-foot wide
To do that, first you need to forget about all best practices and problems that have been fixed and issues regarding quality of life and even safety.
No one bothers building little 10-foot wide streets because that's an appalingly bad idea. Slums aren't known for their quality of life, and no emergency service can pass through 10-foot wide streets.
You're a former boring engineer talking about issues that you know nothing about.
People bother to build little narrow streets all the time in non-slum areas, and their emergency services work fine. It just doesn't happen in North America.
> This is true, but the real elegant solution is to build everything closer together by an order of magnitude, thereby raising the number of destinations in an N minute walking radius and eliminating the need for tunnels. [...] We should keep building cities the way people did for thousands of years, with mostly little 10-foot wide (building-face-to-building-face) streets and a very few larger boulevards.
That's what we have in Europe and it doesn't solve anything.
I only works when the size (diameter) of the city is small. Then a single point in the centre of the city can irrigate the whole city. And a point to point transportation between the centres of several such cities is highly efficient.
But cities have spread, so now the problems are the same as in the USA, except that when the city keeps repeating the same pattern of density while spreading, it makes those problems even worse (infrastructures are more saturated, because there are more people using them and because they are smaller and rarer). Dense or not, your job is nowadays unlikely to be in the same part of the city and generally not in the same suburb either.
There is no benefit in having density on a wide area. What worked when the city was built (or slowly developed into) and was 1-2 km wide was challenged when it grew to 3-5 km wide, and stopped working now that the city is 10-20km wide.
The denser the area, the slower the transportation: be it cars, buses, trains, bicycle, foot, whatever: everything moves slower in dense areas. And there is only so much that happens to be closer and more or less compensates the loss of speed. The rest suffers the density slowdown penalty in full.
I very often read Americans here, who write the same thing you did. It sounds like you all think there is a magic bullet: densification of your suburbs and suburb-like urbanisation. Let me tell you that if you densify this way, you won't solve anything, you will even make everything worse, for you will concentrate more people everywhere around the centre, in a neverending slick of density, and all those people will need or want to commute to other neighbourhoods daily, and you won't be able to offer efficient mass transit for most O-D in those newly densified areas.
You often have a rose-tainted view of European and Japanese urbanisation. Problem can have a different nature, or a different reason, but they exist as well and are as important.
Former tunnel boring engineer here.
This is true, but the real elegant solution is to build everything closer together by an order of magnitude, thereby raising the number of destinations in an N minute walking radius and eliminating the need for tunnels. If your urban design depends on cars-in-tunnels, it's a "code smell" that you've made a grievous system-scale architectural error.
We should keep building cities the way people did for thousands of years, with mostly little 10-foot wide (building-face-to-building-face) streets and a very few larger boulevards. This is how Venice works. This is how Tokyo works. This is how lower Manhattan works, and it's awesome. LA's streets are probably ~100 ft between building facades, on average, so we could infill a bunch of little narrow streets of buildings in each one, raising destinations-per-acre by ~an order of magnitude or maybe more.
This destroys demand for transit by inspiring a modal shift to pedestrianism, and now you have a much smaller problem to solve. You can take all the tax revenue from the new buildings in your newly-densified city, and the money you saved on paving/traffic lights/street upkeep, and use it to build a real 12-trains-per-hour, quad-tracked, express-and-local service, 24 hour subway. Elon's Boring company can dig the tunnels for these if you want.
If you have money leftover you can build through-core commuter rail, that comes from the northern suburbs and goes through downtown out the other side to the southern suburbs, with a one-seat ride. If you still have money leftover you can give it to the homeless or something; under no circumstances should anyone ever spend money on putting cars in tunnels, which is one of the all time dumbest ideas and a prodigiously ugly solution to a prodigiously ugly problem.