I think your research is lacking. HVDC is still mainly used for submarine cables and to link different AC grids.

Where it is used for long distance transmission (such as in China for the 3 Gorges dam), it is still utilized as an overhead cable.

The reason for this is....cost. Burying cable is expensive, plus you can't run them at as high a voltage as an overhead cable.

So again I ask you if we can't allocate enough money for improving our coventional overhead grid and link in large scale onshore wind projects, how does wasting money on burying things make sense.

Even the awea doscument you linked to says the following:

"Green power superhighways could include any
combination of high-capacity Alternating Current (AC)
and Direct Current (DC) lines, and it is not our intent
to promote a specific technology in this paper."

further on the following pages it advocates using 765KV OVERHEAD lines.

I get it that you like burying stuff, but please don't quote stuff that fails to back up your argument.

@bradshsi While I agree burried power is not the ideal solution, it is nonsense to dismiss DC on the basis of cost. HVDC is used in many places because of cost. Here is a paper which advocates a "green" HVDC grid across europe:

http://www.iset.uni-kassel.de/abt/w3-w/projekte/LowCostEuropElSup_revise...

and here is one that cites several other sources advocating DC in the states:

http://www.awea.org/GreenPowerSuperhighways.pdf

As for burring it, a well designed buried system has fewer problems than an above ground system which is subject to the weather, and new technologies can make faults easy to find, minimizing disruption to traffic.

The answer to the problems of intersections and lack of 'alongside' space is visible to everyone who takes a cab from JFK into Manhattan - the elevated rail line built on piers above the median of the Van Wyck Expressway. Sure, the JFK Skytrain itself was a colossal waste of money since it only goes to Jamaica, but it does at least demonstrate the practicality of adding rail to existing roads even where space is tight.

The principle is fine. For the detail just ask the Swiss, they sorted it all out decades back.

Just a point about burying electrical cables under highways.

First off, burying them under something that would cause tremendous disruption if you need to dig it up to fix a fault, doesn't seem like a v smart thing to do.

Second, you can't bury conventional AC high voltage cables for long distances as the extra capacitance eventually would result in no useful energy being transmitted.

You need to convert the electricity from AC to DC (and back again at the other end), which requires large expensive equipment.

If we are already struggling to find money to build above ground grid infrastructure to connect to large scale wind generation projects, adding significant additional cost to bury it, seems like a non starter to me.

In some places, the rail line could go down the middle of the Interstate, mitigating its impact on the landscape. This wouldn't work inside cities, of course, but out in the country the dividing strip can be quite wide. The emergency turnarounds would have to tunnel under or bridge over the tracks, but that's no big deal if you're already doing a massive infrastructure project.

Of course, the idea of running major electrical trunk lines along the interstates has a lot of merit, for all the reasons mentioned in the article and more besides—not only could we boost capacity, but also redundancy, which is sorely needed.

I'm trying to imagine how a railroad line, running parallel to an interstate, would loop around interchanges. In mountainous terrain, a high-speed railroad has to be more level than an interstate and straighter than an interstate. And as Gulliver points out, there's not much space alongside many interstates.

An alternative would be to utilize existing railroad rights-of-way which are everywhere, and are often under-utilized. The result would be slower than a Shinkansen or TGV line, but even if pre-WWII speeds were re-created, that would still be an enormous improvement over the status quo.

For example, the historic Pennsylvania Railroad main line (NYC-Phil-Pittsburgh-Chicago) has enormous potential. It was built to be four tracks wide, and currently there are only two tracks. The occasional Amtrak trains that use it get bottom-ranked priority and have to pull into sidings to let freight trains pass them. There is so much that could be done with this right-of-way, and I suspect there are similar opportunities in other parts of the US.

However, the broader point is valid -- the US is not spending much on rail infrastructure (nor is my country of Canada, either). There is a neverending series of consultancy reports espousing grand proposals, but still Amtrak operates a skeletal network on a shoestring.