Yes, we are programmers, and are philosophically inclined to solve things through clever centralization.

That doesn't mean it's the only, or the optimal solution. Roundabouts depend on decentralized control to achieve very similar goal. (Though without, by the way, the pretty nasty failure modes should that box, or the power, go down.)

It's all handwaving without experimental studies and economic analysis. The numbers for roundabout are much better established than the smart systems, which are still experimental in nature.

For that matter, how much is that cost? The proposal at http://readwrite.com/2014/01/22/ai-traffic-lights-intelligen... is "$20,000 to $40,000 per intersection" for 'a box with a computer in it'.

From http://safety.fhwa.dot.gov/intersection/innovative/roundabou... , "The average construction cost of roundabouts is estimated at approximately $250,000". That gets its numbers from http://www.fhwa.dot.gov/publications/research/safety/00067/0... which says:

> Recent roundabout projects in the United States have shown a wide range in reported construction costs. Assuming “1998 U.S. Dollars” in the following examples, costs ranged from $10,000 for a retrofit application of an existing traffic circle to $500,000 for a new roundabout at the junction of two State highways. National Cooperative Highway Research Program (NCHRP) Synthesis 264 (3) reports that the average construction cost of 14 U.S. roundabouts, none being part of an interchange, was approximately $250,000. This amount includes all construction elements, but does not include land acquisition.

Elsewhere I gave links to places which said the installation costs for a roundabout were more expensive than signals. I don't know if the extra 5-10% price of the "box with a computer" changes the balance.

I tried to get numbers for the cost of a intersection. from http://azdot.gov/business/engineering-and-construction/traff...:

> A modern signal can cost taxpayers between $80,000 and $100,000 to install, depending on the complexity of the intersection and the characteristics of the traffic using it. On top of this, there is the perpetual cost of the electrical power consumed in operating a signalized intersection 24 hours a day. This cost now averages about $1,400 per year.

However, that appears to be for the dumb light, and not one with 'cameras and network connections' or even magnetic sensors. From http://www.masslive.com/news/index.ssf/2009/02/450000_traffi... :

> A request to spend $450,000 to install a new traffic signal on Easthampton Road remains an option for the City Council.

> And while the price tag might seem high for one traffic light, city officials insist that's the going rate to design and install such an item.

> "They're smarter controllers than they ever were in the past," Department of Public Works Superintendent William D. Fuqua said yesterday.

It's definitely not clear to me that the high-tech, interconnected system you desire is cheaper or more effective than roundabouts. (Again, there are clearly place where signals are more effective. I am not saying to only use rounabouts.) I would be happy to read any evidence you have which says otherwise.

This also means I don't think you can call out "environmentalists" for not yet pushing for your high-tech dream to come to fruition. Mind you, some of those environmentalists are pushing for "complete streets", which is yet another way to achieve comparable goals of more effective use of public roads.