Prospective owners of the Chevrolet Volt and Nissan Leaf shouldn't get too excited about driving in California carpool lanes as soon as they take delivery. Late Tuesday night California Gov. Arnold Schwarzenegger signed SB 535 into law, extending access to the high-occupancy-vehicle (HOV) lanes to certain very low and zero emissions vehicles. This new class of vehicles known as Enhanced Advanced Technology Partial Zero Emissions Vehicles (enh-ATPZEVs) and includes plug-in hybrids like and battery electric vehicles like the Leaf and Toyota's Prius PHEV.

Unfortunately, there are some caveats. SB 535 doesn't take effect until January 1, 2012 and even then only 40,000 of the special stickers needed for HOV access will be made available. In order to qualify, the vehicle has to be rated as an enh-ATPZEV, which brings up the second problem for Volt drivers. A General Motors spokesperson confirmed that the 2011 and 2012 Volt will not be enh-ATPZEV certified. The requirements to earn the enh-ATPZEV label are significantly tougher than the standard ATPZEV. Given the escalated development of the Volt, GM didn't have enough time to calibrate and verify that the plug-in hybrid would meet the standard over a 10-year/150,000-mile period.

That's also why the Volt battery only has the eight-year/100,000-mile warranty required for the non-enhanced ATPZEV. GM spokesman Rob Peterson verified that the Volt will be updated to enh-ATPZEV in mid-2012 when the 2013 model is introduced. In the meantime, you'll just to make sure to bring a friend if you want to ride in the carpool lane.

*UPDATE: Plug In America's Jay Friedman pointed out to AutoblogGreen that the Leaf is not an enhanced ATPZEV. Pure electric vehicles are not covered under SB 535 and are instead subject to AB 1500, a separate bill, and are in the pure ZEV class. AB 1500 extended HOV access for all ZEVs (including all pure electric vehicles) and CNG vehicles, which was supposed to end this year, until 2015. Therefore, he writes:
SB 535 does not include electric vehicles in the 40,000 HOV sticker cap and AB1500 takes effect immediately extending the sunset date from 12/31/10 to 1/1/15 (which is very important vs the start date for SB535 which is 1/1/12).
[Source: General Motors]