1) Send a letter to your MP In it pick on a local piece of road that has numerous sets of traffic lights. Advise them that if they syncronised the lights they would save on the county's CO2 footprint, (Constant 40 mph is better than zero - 50 - zero - 50 etc)
2) Fit a LPG conversion LPG is about 50% of the petrol cost
3) Smaller car / smaller engine for local trips
Ian