California hybrid owners who registered for stickers allowing them single-occupancy HOV access are enjoying their final hours of the perk today, with this evening’s commute presenting perhaps the final opportunity for Prius drivers in the state to leave their gas-loving peers in the dust during high-traffic periods.

According to the DMV, after July 1, hybrids with the now ubiquitous yellow HOV sticker “will no longer be allowed to operate in an HOV/carpool lane unless the minimum passenger requirements are met. This expiration date will not be extended.”

Taking the place of gas-electrics in the carpool lane will be fully electric, plug-in hybrid, and compressed natural gas cars. Last August, the California senate passed a bill granting a six-month extension of the perk to July 1, 2011, saying at the time that extension would give California hybrid owners time to purchase the next generation of electric cars and plug-in hybrids coming to the market.

Those cars have arrived. The all-electric Nissan LEAF (which began deliveries to California drivers last December,) and the Toyota Prius Plug-in Hybrid (expected in 2012,) both qualify for stickers. The 2011 Chevy Volt is not currently eligible, but is expected to receive the necessary certification for the 2012 model.

California first introduced its hybrid HOV law in 2004, allowing as many as 85,000 gas-electric drivers to qualify for a yellow sticker granting them the special privilege. Within a few years, the allotted stickers were gone—new hybrid buyers in the state have been unable to obtain one since early 2007—and California hybrid sales had rocketed to more than 90,000 per year.

But the effectiveness of the program was never clear. Though it saw the rise of hybrids in California and likely helped to raise awareness of the technology, the primary driver for fuel efficient vehicles among consumers has always been cost—both the price of fuel and the additional premium that drivers can expect to pay for cars offering superior fuel economy.

Regardless of the effect of the sticker on boosting hybrid adoption, it can be seen as a positive sign that California’s hybrid market is likely poised to hit record levels in the coming years, as automakers work to meet rising state and federal fuel economy standards, and satisfy heightened consumer demand for fuel-sippers.

As for early hybrid adopters, the good news is that they can re-obtain their carpool supremacy by becoming among the first to purchase a plug-in electric vehicle. That prospect may not be enough to make plug-ins as commonplace in California as hybrids have become, but it certainly can’t hurt either.