Using air rights over streets

[RPfresh]

I know that in Portland there is a firm that purchases air rights over parking lots and builds new buildings; I am not an architect, but it seems like the same thing would be possible over your average downtown street. This would open up lots of new real estate in the city, for housing, offices, parks etc. as anywhere that there is open asphalt would be a potential construction site. I know that cities like Calgary and Minnesota have raised walkways over streets, so I'm just talking about something like that but a whole building. I have a vision of a city that has no visible streets at all, and is two stories up off the ground...any thoughts?

[Gotta Speakup]

You get points for ingenuity, but building over streets would be bad for pedestrians. People don't like walking under buildings. There is a catch 22 involved. the most valuable streets would be those in downtown areas, but building over the streets would kill the downtown vitality that gives value to those streets. You might also get sued by the property owners and abutters who suddenly find their sunlight blocked. Not to mention the setback requirements!

A lot of my relatives in the Bay Area don't even like idling at stop lights under overpasses because of the fear of earthquakes. Think how they would react to driving under buildings the whole time.

Boston has had some success in building over the Mass Turnpike that comes into the city (the Prudential Center and Copley Place) but other efforts to bild over the highway have proved too expensive and technologically difficult.

[Seana]

I know that in Portland there is a firm that purchases air rights over parking lots and builds new buildings...

Are you referring to the Portland, OR firm that owns one or more of these mixed-use developments:
http://www.hdc1.org/downloads/bhcd-color-pages.pdf

I know that cities like Calgary and Minnesota have raised walkways over streets, so I'm just talking about something like that but a whole building. I have a vision of a city that has no visible streets at all, and is two stories up off the ground...any thoughts?

My first thought: it's not really a transportation planning topic. You're talking about building structures over roads that already exist, am I correct? It's a zoning topic if you're referring to individual buildings; a 'Make No Small Plans' if you're envisioning a great many buildings or a whole city.

My other thoughts about your whole-city idea: safety issues, national security issues, massive pollution, carbon monoxide poisoning, extensive removal of greenery, destroyed ecosystems, etc... though I'm sure that somewhere in the world they'd go for it... <insert weeping Seana emoticon>

[jmello]

Boston has quite a few buildings located over the Massachusetts Turnpike and other freeways. There is a plan to cover the entire turnpike within the City of Boston.

Check it out here:

http://www.cityofboston.gov/bra/Plan...Init&InitID=43

[Suburb Repairman]

I tend to agree that this might be seen more in the Make No Small Plans forum. SR

[CJC]

I don't like the idea of putting buildings over city streets, but building over freeways is good stuff, IMO. It's a good way to heal neighborhoods that were torn apart years ago by a freeway being cut through.

San Francisco is working on a plan to deck over part of a freeway in the southern portion of the city (it's on page 16):

http://www.bayareavision.org/marketp...0Book%20SF.pdf

In Reno, NV, there is a nice Walgreens built on a deck over a freeway as well that I saw a few months ago.

[Cardinal]

I have seen buildings constructed over downtown streets and interstate highways. The first only works in a handful of instances, because of the reasons stated above. The second can be a missed opportunity in many cities. It would be especially nice to see it pulled off in a way that maintains the street wall along public streets crossing the highway. The difficulty is in establishing foundations for the building/bridge and continued maintenance.

[RPfresh]

Are you referring to the Portland, OR firm that owns one or more of these mixed-use developments

I read about the firm I'm referring to in a book - it is Sienna Architecture, I believe.

I kind of get that there are lots of problems with this kind of proposal, but let me play angel's advocate for my own idea. As far as the argument that pedestrians would be put in danger or made uncomfortable - what if we banned pedestrians completely from the underlying car-only area and sort of forced the pedestrian street upwards onto the third story? Here we run into problems of displacing first-story businesses, which means that it would be hard to do in a preexisting neighborhood or downtown street. But maybe businesses could be 'relocated' to other low-rent commercial space for the sake of urban renewal

Also I kind of wonder about the pollution problems that are being spoken about. What do they normally do for tunnels, or are you just supposed to never roll your window down while you're in there? It seems like a good vent system could push the air out to the appropriate place.

[planr]

what if we banned pedestrians completely from the underlying car-only area and sort of forced the pedestrian street upwards onto the third story? Here we run into problems of displacing first-story businesses, which means that it would be hard to do in a preexisting neighborhood or downtown street.

If one developer had many adjacent (or proximate) parcels, you could create a 2nd or 3rd floor pedestrian mall and retail space. Hong Kong would be a great example of this (extreme example, I know).