The Economist has published a remarkably detailed analysis of the history and future of hybrid automobiles (while nominally only available for subscribers, FuelCellWorks.com has reprinted the article in its entirety; this may be a "read it while you can" situation). The piece is notable for several reasons: a clear explanation of the differences between different hybrid vehicle technologies; a digression into the history of Toyota's clean vehicle research leading to the Prius; and a discussion of the plausibility of diesel-based hybrid cars. I've been following the evolution of green vehicle technology for awhile, and I still learned a lot from this article.
The article also describes a next generation hybrid technology referred to as a "plug-in hybrid:"
The next step may be the "plug-in" hybrid, which is not the backwards step its name suggests. Unlike the electric cars of the 1990s, none of today's hybrids needs to be plugged in - but if plugging were an option it would be a good idea. Andrew Frank and his team at the University of California Davis' Hybrid Electric Vehicle Centre are working exclusively on plug-in hybrids, which can operate as pure-electric vehicles over short distances (up to 60 miles, with a large enough battery pack) but can switch to a hybrid system when needed. Since the average American driver travels about 30 miles a day, plug-in hybrids could be recharged overnight, when electricity is cheaper to produce, and need never use petrol at all, except on longer trips.
According to studies carried out by the Electric Power Research Institute (EPRI), a non-profit organisation based in Palo Alto, California, plug-in hybrids could be one of the cleanest and most efficient kinds of car.
The plug-in hybrid seems a good solution for the "usually drive less than 30, want to drive more than 300" problem -- drivers who regularly use their cars only for short trips, but don't want to be limited to only short trips.