There is no clear path to an alternative energy future, or on the timing and cost of the transition to an electric future based on renewable energy. There is also competition between the existing technologies and other energy carriers (hydrogen, pure electric, plug-in hybrid, biofuels), and each may be supported by separate government interventions that to some extent exist in isolation. Improvements in the fuel efficiency of traditional internal combustion vehicles have been robust, accelerated by regulatory requirements and tax incentives, eroding the short to middle-term business case for fossil fuel alternatives, particularly if the energy used still relies on nonrenewable sources.