The California Air Resources Board is considering extending production deadlines for automakers under its zero emissions vehicle (ZEV) standard. Environmentalists were quick to label the proposal as a rule weakening. However, an extension could help leverage production of plug-in hybrid electric cars because the rule change would ease the criteria that allow their use as a substitute for ZEVs. The Air Board staff outlined the proposal to relax the standard in a July 24 \u201cconcept paper\u201d released at a meeting that day. \u201cThese requirements may not be appropriate at this time,\u201d explained Tom Evashenk, Air Board mobile source division staff member. However, the staff\u2019s proposed changes could boost the prospects for automakers to roll out the plug-in hybrid vehicles, which is of increasing interest to the electric power industry. Under the existing rule, automakers unable to produce enough of the zero emissions fuel cell vehicles may comply by producing a variety of substitute vehicles that approach zero emissions. Each of these vehicles is given partial credit toward one zero emissions vehicle. Thus, automakers can effectively avoid producing pollution free models if they build enough substitutes. These include plug-in hybrids, other hybrids, and neighborhood electric vehicles. A key electric vehicle organization representing utilities endorsed the concept of providing such incentives for plug-in hybrids. \u201cThey do provide technology advancement for the pure battery electric vehicle,\u201d said Dave Modisette, California Electric Transportation Coalition executive director. He urged the Air Board to consider increasing zero emissions vehicle compliance credit for automakers that sell plug-ins in California. The zero emissions vehicle rules, adopted by the Air Board in 2003, envisioned automakers producing hydrogen fuel cell-powered cars. Automakers backed the rules but only after beating back an earlier version of California\u2019s zero emissions vehicle standard. At one point, the state mandate envisioned that by 2003 ten percent of all new cars sold in California would be battery electric vehicles. The Air Board plans to develop and adopt final changes to its zero emissions vehicle rule by the end of the year. The standards then would become applicable in a variety of other states that have opted to enforce California motor vehicle standards in place of federally enforced standards.