The California Air Resources Board is set to vote today on a staff proposal to substantially reduce the number of zero-emission vehicles, or ZEVs, the six major car companies would have to produce for California by 2014.

To keep its long-term goal of cleaning the air and to achieve more recent mandates to reduce global warming gases, the board should reject its staff's recommendations and stand by its ZEV commitment.

Pure ZEVs are cars that produce no tailpipe pollution. They are usually powered by batteries or by fuel cells. Under current rules, car companies are required to produce 25,000 ZEVs between 2012 and 2014. CARB's staff wants that number reduced by 90%, to just 2,500.

To make up for the ZEV reduction, the staff proposes to increase by 75,000 the number of partial zero emission vehicles that car companies would have to produce. They are primarily plug-in hybrids, cars that run on both batteries and gasoline.

Plug-in hybrids are a good automotive innovation. They are not pollution-free, but they use less gasoline than current hybrids. The board is right to encourage their development. But it should not do so at the expense of pure ZEVs.

Only when the state mandates more pollution-free cars on the road can it encourage a serious level of investment in fuel-cell and battery technology and the kinds of infrastructure both technologies need to make pollution-free cars commercially viable. Fuel cell-powered pure ZEVs will need hydrogen fueling stations and battery-powered ZEVs will need charging stations. Those kinds of infrastructure won't be developed or built if the state cuts back its ZEV mandate.

Car companies have had the know-how for decades to build pollution-free cars. Recognizing that, California regulators first required car companies to produce ZEVs in 1990. Back then, CARB required that 10% of cars sold in California by 2003 be pollution-free. In the 18 years since that first aggressive mandate was imposed, the state has steadily weakened its commitment.

Every retrenchment has been a blow, not just to automakers who invested in innovations, but to the battery industry and those who sought to invest in fuel-cell technology. If the air board goes along with its staff recommendation to cut ZEV requirements by 90%, urgently needed investment in clean technology will dry up once again.

Such investments are needed more than ever. When the state air board first mandated ZEVs, California was seeking a way to reduce air pollution. Since then, the global-warming crisis and man's contribution to it has become more widely recognized and understood.

California has enacted a historic law that seeks to reduce greenhouse gas emissions, a major contributing factor to global warming. Pollution-free cars, ZEVs, can play a crucial role in reaching the state's goal of reducing greenhouse-gas emissions.

For the state air board to pull the plug on ZEVs at this point sends exactly the wrong message. The board should reject its staff's recommendations and keep the pressure on car companies to produce cars that don't pollute our air or contribute to global warming.