When the United States was going through the highway boom in the 50s and 60s, there were a lot of planned routes through every major city. Most came to fruition, but many were not constructed due to community opposition or lack of funding. Interstate 78 in NYC is one of those unbuilt routes. It currently ends in New Jersey at the Holland Tunnel entrance, but there were plans for it to go through the tunnel, through Manhattan via the Lower Manhattan Expressway (unbuilt), over the Williamsburg Bridge to Brooklyn, via the Bushwich Expressway (Unbuilt) to Kennedy Airport, then north to the Bronx. The map above shows part of the route.
I actually think about, how NYC would be different if all the routes that were planned were actually built. It would have been a very different place. These additional routes would have eased congestion on the road network, but destroy many communities. Furthermore, if you build new roads it creates an induced demand where more people than before would drive. So these new roads would have eventually become congested anyway.
Canal Street is the arterial street in Manhattan that drivers take to drive between the Holland Tunnel and the Williamsburg & Manhattan Bridges. These drivers exited highways in New Jersey and Brooklyn and have no choice, but drive on local streets.
But is it better to have congestion on the highways and not on local streets? I think so. This is how it is now in NYC. I-78 would have traveled in lower Manhattan connecting the Williamsburg Bridge to the Holland Tunnel. That is a major corridor for drivers to travel between Long Island and New Jersey, but there is no highway link between them. Currently, vehicles crowd the street, sometimes taking over an hour to travel one mile. I cannot imagine that being good for air quality.
The original plans for the I-78 Lower Manhattan Expressway called for an elevated highway for the majority of its route which would require a lot of condemning of homes. That is one of the major reasons to why it was not constructed. It would have been an eyesore like some of NYC’s current elevated highways.
So today NYC is plagued with crippling congestion in its downtown area. I think the only feasible solution that people would support is a underground expressway connecting the bridge and the tunnel. I can see that happening one day because we are delaying a problem that continues to get worse. It would be extraordinarily difficult, but I find it cool to just picture such an achievement and driving through it.
The unbuilt Lower Manhattan Expressway
(http://www.nycroads.com/roads/bushwick/)
(http://www.nycroads.com/roads/clearview/)
(http://www.nycroads.com/roads/lower-manhattan/)