AUGUSTA – Maine’s plan to require that car dealers sell a minimum quota of “clean” vehicles was finalized Thursday with a unanimous vote by the state Board of Environmental Protection.

The rule, known as the zero emissions vehicle plan, requires that, starting with model year 2009, 11 percent of total vehicle sales in Maine must meet strict emissions standards.

Six percent of that total must be hybrids, and the other five percent “clean” gasoline-powered vehicles. Already, nearly 30 models of cars and a few small trucks and SUVs meet the emissions criteria, said Ron Severance of the Department of Environmental Protection.

Over the next five years, automakers can build up credits for the clean cars they sell before the official start date.

The board had initially approved the policy in late 2004 but needed legislative approval to finalize the rule.

Lawmakers gave their approval this session but added a new component allowing auto manufacturers to earn limited additional credits for clean cars they sell elsewhere, making it easier for them to comply during the first few years of the program.