When traveling for work to a conference or meeting out of town, why not consider cutting down on your carbon footprint by taking only public transportation (bus/trains/metro are available in most large cities) or renting a hybrid vehicle to get around town. More and more rental car companies (such as Avis, Budget, etc.) have hybrid vehicles as rental options. Enterprise/Alamo/National also offer a carbon offset program for $1.25/day that goes toward certified offset projects that work to remove CO2 from the atmosphere. In many large cities, there are options for hybrid taxis and limos as well. Do a search in google for your city and “hybrid taxi” or “hybrid limo” and many options appear.