Bring public transport back into public owndership, therefore reducing comptetion in private sector, where corners are cut (dirty old bus stock etc). Stop out of town developments for shopping, leisure etc, which puts pressure on car use, instead regenerate run down inner city areas. Force car companies to convert new cars into LPG and other "greener fuels" just like they introduced unleaded and catalitic convertors. Are just some quick ideas. I am sure their are many more, and to my knowledge they are not Lib Dem or Labour policy ideas.