Why?

Northern Virginia hybrid owners have the privilege of using HOV lanes. Northern Virginia residents who do not own hybrids are buying them so that they may use the HOV lanes. These solo hybrid drivers have crowded HOV lanes to the point that the lanes are not really worth using (article linked by BATN and Planetizen).

Why should California choose this model as its future? To boost hybrids' popularity, sure, but to the detriment of another energy-saving mechanism, carpooling:

In March [2003], a traffic count on the HOV lanes of I-95 revealed 480 clean fuel vehicles -- about 8 percent of the cars that used the lanes at the time. By October, that count on I-95 more than tripled, to 1,700, 18 percent of all HOV traffic and enough to fill a single highway lane for an hour.

The growth in hybrids has helped increase the number of cars on the lanes to 1,900 an hour, beyond their operating capacity of 1,500 to 1,800 per lane an hour.

The HOV lanes are critical to the region's transportation network in part because they allow bus service to run smoothly. If they become chronically congested, slugs [casual carpoolers] and other carpoolers could resume driving themselves, adding thousands of cars to the region's roads.

Could it be that hybrids are now so popular their sales don't really need any legislative boost? And, to repeat an earlier post's point, will solo hybrid drivers ever leave the HOV lane once in?