Different states dominate different realms of energy policy, although their powers are not evenly distributed. Their jurisdiction comes from their respective roles as regulators of utilities monopolies. One large example is California, which serves as the effective regulatory body nationally for vehicle pollution as well as fuel efficiency standards. This could be due to a combination of factors, including its expansive market size and political tailwinds in the sustainable energy space. Other groups of stands have collaborated on regulatory agreements on other energy policy issues such as oil pipeline safety. While focused regulation by states can be effective, the division of labor within energy policy can lead to some impediments. The relationships between state-level and federal bodies are amorphous with loosely defined rules and lead to drawn-out negotiations, for things such as wholesale power transfers or mandates to rebuild power generation infrastructure that costs trillions of dollars, which take a long time to resolve and may not lead to desired outcomes.