there are still structure issues for all methods mentioned

I use to be a hydrogen fan but it has so many leaps and bounds needed to become efficient, containable, shippable and SAFE (not to mention the volume needed for a container); that it is a very distant dream.

Issues with metropolitan area's and electrics is they would all need a place to plug in and charge...think of all the retrofitting for the metro lots, parking garages etc...its not like these people park in their garage at their homes...and the power company sure isn't going to give away energy for free...so now each spot has to be metered.

Plug in Hybrids (charge overnight) are by far the most efficient and fuel sipping/best solution for metropolitan areas, however the listed issues about still need to be met...the product of Nickel metal hydride batteries is a VERY VERY dirty one (see Prius)...lithium ion however, I don't know that much about.

See why my vote still goes to algae based oil...oil goes to diesels, the other 50% of the algae carcass goes to cellulosic ethonal...all it takes to produce the algae is sunlight, a little bit of water (literally) and some pumps for water flow. Essentially, we still use the sun's energy to grow our fuel.