Last week, Virginia passed yet another extension of its hybrid HOV law, which gives drivers of “clean fuel” vehicles access to the commonwealth’s carpool lanes. The law has been extended annually since its original expiration date in 2006—even as the state’s HOV lanes (and hybrid sales) swell. Could the extensions have anything to do with the fact that, with every registration for access, $15 goes to the state police’s “HOV Enforcement Fund?”

Since the emergence of hybrids in the last decade, several states have enacted similar carpool laws as an added incentive for consumers to embrace gas-electric vehicles. But with fuel prices high and hybrids no longer the newest fuel-saving technology on the block, the argument for keeping around added hybrid driver perks has weakened.

This June, California hybrid drivers will lose their HOV access—a bonus that has been available to 85,000 such vehicles since 2004. But with hybrids all but ubiquitous in many parts of the state, California decided last year to shift the privilege to drivers of plug-in electric vehicles, and push solo hybrid drivers out of HOV lanes. Virginia has long ranked among the top ten states for hybrid sales, which would likely make it among the first to end its HOV incentives—except that it isn’t.

Are Virginia Cops Hooked on Hybrids?

In order to be eligible for full HOV access, a Virginia hybrid must sport the state’s special Clean Fuel Vehicle (CFV) license plate, which is available for an additional $25 fee on top of the annual registration cost. Of that money, $15 goes to the state police’s “HOV Enforcement Fund,” which was established alongside the CFV law to help troopers identify and ticket HOV violators.

When Virginia first began granting solo hybrid HOV access, the state police issued a report (PDF) requesting a $300,000 annual enforcement budget—up from $140,000 the year before. Today, with more than 66,000 hybrids on Virginia roadways, the state income generated by CFV registration fees is adding up. Though information on exactly how many such tags are circulating isn’t readily available, if all 66,000 hybrids were to register each year, the state police budget could rake in more than $900,000 annually from the program.

Hybrid HOV drivers use tags to verify their access, rather than leaving it up to the police to spot the difference between a living passenger and say, an inflatable doll. It begs the question: Howt many additional enforcement dollars are required to keep them honest? But with state budgets tight, raising the additional funds necessary to neutralize the impact of losing that registration fee could be tough—which may explain why Virginia continues to kick the can down the road on the program.

For now, new hybrid owners in the commonwealth can continue to register their cars for CFV designation until June 30, 2011. All hybrids are scheduled to lose access exactly one year from that date—though given recent history, don’t be all that surprised if yet another extension finds its way into law before expiration hits.