But I think it is fair to say that using PHP, especially for large deployments, is not very Kopenhagen.

New Scientist has an interesting piece up about the calculable energy costs per mile for various forms of transportation. Despite the headline (“Train can be worse for climate than plane“), the study it describes deals with highway-based vehicles, too: the authors attempted to integrate not just the cost at the tailpipe (or equivalent) for each mode of transport, but also the costs of developing and supporting the associated infrastructure, such as rails, highways and airports. Such comparisons are tricky, though; a few years back, a widely circulated report claimed that the Toyota Prius had a higher per-mile lifetime cost than the Hummer (see that earlier Slashdot post for good reason to be skeptical of the methodology and conclusions). I wonder how the present comparison would be affected by a calculation of (for instance) how much it would cost to move by plane the freight currently carried by trains.