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Comment by athenot | Hacker News Reader

Cars in tunnels is a great idea, just like the subway: burry it so as to not impact life on the surface.

Unfortunately, it is very expensive to operate that way. The easiest tunnels to build are the ones Paris did for their subway a century ago: dig up the soft limestone under the street, lay tracks, close it up. But you still need to deal with ventilation (especially for non-electric cars), fire suppressant, evacuation, flooding and general maintenance. In the best-case scenario, tunnels are just very expensive.

Then there are places like Atlanta (sitting on granite) or San Francisco (in a fault zone) where things get a lot more complicated.

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I've thought about this. My thought has been, bump the street level up one story to create a pedestrian / bicycle promenade and move building entrances to the second floor. Keep the existing street below intact, with parallel parking etc. Essentially build a boardwalk above a commercial street, so that traffic can flow below. (Though for ventilation purposes, it would be best if most cars at street level were electric.)

Raising the street grade one story has been done before, when flush toilets were introduced in the late 1800's. Notably in Seattle and Chicago but in pockets other low-lying cities as well.

https://en.wikipedia.org/wiki/Raising_of_Chicago

https://en.wikipedia.org/wiki/Seattle_Underground

That reminds me of a 1920s drawing of the "city of the future" that had several levels of roadway with a promenade or pedestrian level on the third or fourth story: https://worldstreets.files.wordpress.com/2010/07/future-city...

Downtown Chicago comes pretty close with subway on the lowest level, trucks and commuter rail above that, and cars/pedestrians on the surface. There is also a large network of pedestrian tunnels which is useful in winter (and when coming from aforementioned commuter trains).

And until 2003, there was even an airstrip only 2mi from downtown.

Montreal's Underground City is a pretty great example of how to give public pedestrian connectivity underground in winter. Well worth checking out: https://en.wikipedia.org/wiki/Underground_City,_Montreal

As a somewhat frequent visitor to Chicago, I like the idea of the pedestrian tunnels, but they don't seem like a practical way to get around.

They're basically the separately-operated basements of stores, hotels, and office buildings networked together. Usually one of them between you and your destination will decide to lock the doors.

I've found myself nearly under my destination, encountering a locked door, and having to backtrack and find my way out through a fitness club.

For an extreme (and somewhat tongue-in-cheek) version of that, see The 5th Element. Everything happens in the sky and street-level becomes this shady area filled with trash and thugs. :)

Or Star Wars' planet Coruscant, or Futurama's New New York.

Or Deus Ex: Human Revolution's Shanghai

Yea it's also a pretty common sci-fi / cyberpunk fantasy city design dating back to Fritz Lang's Metropolis, influenced by the Art Deco "city of the future" ideas like this floating around at the time.

In NYC at least the lower levels are already present. But the only part where we got the pedestrian level correct so far is the High Line... which has been hugely successful. There's really no reason these types of park-like promenades only have to be built on top of existing disused structures however. More could be built, it's just that people need to understand that there is return on investment for building an elevated pedestrian-only street level.

Except that in most cities including New York it's going to be difficult to build something like that in the absence of an existing structure and right of way. The High Line is also in effectively a post-industrial area which is now highly gentrified but wasn't previously exactly prime real estate. And it's still not really located for day to day pedestrian movement as opposed to recreation.

Totally agree, it would be a political and engineering mess to try and implement on an existing busy street. The conditions were very ripe to experiment with the high line.

Not an easy thing to develop certainly, but relative to the cost and level of engineering effort needed to build new subway tunnels, I'm surprised that adding transportation improvements at street-grade and then bumping the street up one level, isn't something that ever gets considered. We could run effective BRT through Manhattan, or surface light rail to solve the crosstown transportation problem.

Imagine how much easier getting from Queens and Brooklyn to the Lincoln and Holland tunnels would be by car or bus if say 39th St, Canal St moved the pedestrians to an elevated walkway. What if Times Square's tourist bottleneck could be eliminated by raising Times Square?

Anyhow, unlikely to happen probably ever, but fun thought excercise

Sacramento did that because of flooding.

"I've thought about this. My thought has been, bump the street level up one story to create a pedestrian / bicycle promenade and move building entrances to the second floor."

This (sort of) already exists in Minneapolis (and to a much smaller extent, St. Paul and Duluth) courtesy of the skyway system.[1]

It's very well done and has created a completely separate urban ecosystem overlaid on top of the existing, street level, downtown.

[1] https://en.wikipedia.org/wiki/Minneapolis_Skyway_System

Is it all indoors or is it outside as well?

Or you have hot humid cities like Fukuoka and Taipei that move a lot of the pedestrian and retail underground. I think the best solutions depend a lot on the local weather conditions.

To avoid accidents and other dangers, I'd see a mechanism where you park your car in a pod, and the pod is on rails, and it is getting routed automatically to your destination, that way even "dumb cars" could use it. There's already a system in France where you can park your car on a train, but loading/unloading isn't optimized at all, it's like loading/unloading a ferry : some batch processing. A steaming process would be more efficient

That wouldn't remove the need for ventilation and other things you mentioned if that system is underground. But it could be above the ground , on buildings 2nd floors, where the first floor would be retail stores and whatnot

> you park your car in a pod, and the pod is on rails

Why not have seats on the pod, that way you don't have to ferry around a 2-tonne car. Indeed if you have solved smart automation, why have rails at all? Presto, you arrive at the idea of self-driving taxis as a public service.

For the autonomous cars, it'd be interesting if they could do the equivalent of what computers do by "binding to a domain", letting things like these loaders connect to them and "drive" them onboard.

Really, the car would (should!) still be driving itself—it's the thing that gets certified on how to handle safety issues, after all; the car would just be given a dead-reckoning location target by the zone controller, which the car would get to as best it knows how, with the zone controller scanning to "see" when it had successfully boarded, just like with a human-driven car.

If there were few-enough human-driven cars, you could have a team of valet staff accompanying the train, acting as glue for the few human-driven cars in the pack.

When building a city from scratch you can cut-and-cover everything, and you can choose somewhere with good soil conditions for what you want to build.

Would you build rail transit underground in a new city? A large part of why subways are even things to begin with was because they were added late in the development of most cities that justify building them. Newer cities like Dallas have above ground commuter rail exactly because the city still had room to build it above ground.

If anything, it is much more valuable to segment the city in ways that you don't need subways or roads. You should have districts that are internally navigable strictly by foot, bikes and tram between adjacent districts, and only have rail / road when going beyond the local microcosm of city.

You want greenery anyway, you might as well put it in the bounding lines between regions of your city and have the roads / rail between those to minimize noise pollution outside of the transit hubs.

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