Toyota Motor Co.'s (NYSE: TM) Prius hybrid is by far the world's most successful hybrid vehicles, with sales numbering over one million units. In addition to the great gas mileage these gas/electric vehicles provide, could these cars become even more efficient? According to Toyota, that's already in the works.

The Japanese automaker was featured in Japan's Nikkei newspaper yesterday as saying it will begin installing rooftop solar panels on its next-generation Prius vehicles. Starting with the high-end model, these solar panels will be used to power the air conditioning systems of the car. According to the Nikkei report, these solar panel arrangements may start showing up as next spring.

If Toyota can pull this off, it will mark yet another milestone in automotive history: including solar panel technology in a mass-produced car. It could also set off a trend to power automotive subsystems directly from solar power instead of internally generated power from the gas engine/alternator system or the onboard electric motor. Solar power is abundant and free -- why not use it as much as possible?

Now, where are the other automakers with this? General Motors (NYSE: GM)? Ford Motor (NYSE: F)? A show of hands, please.

Detroit's big three automakers are meeting with federal officials this week to try and address the mandate of 30mpg trucks and 35mpg passenger cars by 2020 (and beyond). Most likely, Ford Motor Co. (NYSE: F), General Motors Corp. (NYSE: GM) and Chrysler (in the process of being bought by Cerberus Capital Mgmt.) will state and build cases that it will be very unlikely that such fuel-efficient cars and trucks can be made in such a short time. In fact, all automakers that sell cars and trucks in the U.S. need to come to a common front or this new regulation will be completely doomed (according to industry watchers). Moving outside the fuel economy arena, though, are there even bigger problems with U.S. automakers these days?

How about a complete surplus of dealers? The actual number of Ford, GM and Chrysler dealers, based on autos sold, is huge: GM has nearly 7,000 dealers, Ford has 4,200 and Chrysler has 3,700. Based on sales of domestic cars and trucks in the last few years and the increasing presence of Toyota Motor Co. (which is outselling almost every other manufacturer in the U.S.), these numbers -- almost 15,000 dealers -- seem a bit high. Sure, the big three are in the process of reducing the ranks of dealers to fit current (and projected) business needs as the personal transportation market continually changes, but it can't happen fast enough.

Compare this to Toyota, whose dealer count in the U.S. tops out at about 1,400 dealers, while Toyota vehicles are just as (if not more) popular than most domestic nameplates from the big three. What has Toyota done to keep its dealer count low while selling more cars? Responding to the market's needs a lot faster? You bet. Marketing itself as the most reliable and dependable automaker? Sure. Can the big three recapture business from Japanese automakers by thinning the ranks of dealers? That's a start, but it's not any more than that.