Okay everyone, here it is; I'm no doubt repeating it from a comment I've made here earlier. Now it gets its own diary. Anyway:

1) The government starts a car company.

2) The car company makes only electric cars which will come with their own solar panels.

3) Everyone who owns a fossil-burning car gets an offer. You can trade in your fossil-burning car for an electric car at no charge.

4) At some point the gas pumps are shut off.