<P> Air is susceptible to the Tragedy of the Commons, but that can be overcome with policy tools . In their book Environmental Law and Policy, Salzman and Thompson describe these policy tools as the "5 P's" - Prescriptive Regulation, Property Rights, Penalties, Payments, and Persuasion . </P> <P> Throughout the years there have been some tensions between the US EPA and the California EPA with disagreements centered on California's Smog Check Policy (The Press - Enterprise, 1997). One disagreement has been over where smog checks are performed . The EPA believes that smog checks and smog repairs must be done separately, to avoid conflicts of interest . </P> <P> For years, California has been asking the US EPA to approve a waiver allowing it to enforce its own greenhouse gas emission standards for new motor vehicles . A request was made in December 2005, but denied in March 2008 under the Bush administration, when interpretations of the Clean Air Act found California did not have the need for special emission standards . However, shortly after taking office, president Obama asked the EPA to assess if it was appropriate to deny the waiver and subsequently allowed the waiver . US EPA's interpretation of the Clean Air Act allows California to have its own vehicle emissions program and set greenhouse gas standards due to the state's unique need . </P> <P> Car manufacturers have been strongly opposed to the emission standards set by California, arguing that regulation imposes further costs on consumers . In 2004, California approved the world's most stringent standards to reduce auto emissions, and the auto industry threatened to challenge the regulations in court . The new regulations required car makers to cut exhaust from cars and light trucks by 25% and from larger trucks and SUVs by 18%, standards that must be met by 2016 . The auto industry argued that California's Air Resource Board did not have the authority to adopt such regulation and that the new standards could not be met with the current technology . They further argued that it would raise vehicle costs by as much as $3,000 . The agency, however, countered that argument by saying that the additional costs would only be about $1,000 by 2016 . </P>

When does a car need to be smogged