At present I see no technologically developed replacements for liquid fuels in these uses.

electricity and electric motors.

Go and stand on a bridge over a six lane freeway and count how many passing vehicles are electrically powered - as usual you are talking complete bollocks!

The electric motors you suggest need an adequate, low cost, high capacity battery of some sort - currently none come anywhere near gasoline and diesel for energy density, ease of use and cost.

It is not wise to assume personal electric vehicles will ever be cost competitive with ICE.

I used to rely on an electrically powered vehicle for most of my commute to work, when I lived in Newcastle and was commuting to a branch campus on the NSW Central Coast.

Of course, batteries were not an issue for those ...

... in any event, the "in these uses" in the comment further above referred to mechanized agriculture and construction machinery. That is a quite different problem to moving the people and freight that current use the Interstate.

In mechanized agriculture in particular, biofuel seems a plausible technology for including in the mix when developing alternatives to a petroleum based agriculture.

John,

You don't need new technology. It's already there. Ordinary cars (not the expensive hybrid technology) that run 50+ mpg can be bought as we speak. As a matter of facts, I have one, a second hand. The model has been on the market since 1997.

VW has introduced the Lupo 3L years ago. It runs 3 liters of diesel on 100 km. That's 75 mpg.

It's already there. No need for inventions. No need for break throughs. And it is much cheaper than a 15 mpg SUV. The average costs of cars like this are well below 10.000 US$.

And if you are American and want something a bit bigger:

http://www.whatcar.co.uk/car-review-pictures.aspx?RT=56&U=1

I get 45mpg (Urban commute) to 60mpg (Motorway) from this diesel, which has a larger cargo capacity than a lot of SUVs, as well as vastly better cornering. Modern diesel technology is something that might actually make a difference in the US - it's the reason why many European countries have seen flat or even slightly dropping oil usage in the past decade, despite increasing populations and passenger miles.