For those of us fortunate enough to have efficient public transportation available, the question often arises as to the environmental effectiveness of the options. That is usually a very complicated question, with complicated answers, but I was very pleasantly surprised to discover this: The BART Carbon Calculator. BART stands for Bay Area Rapid Transit, and is the regional commuter rail system for the San Francisco Bay area. On peak days, BART transports close to the equivalent of all daily domestic flights in the United States! So, while planning a trip to the Oakland Airport this morning (to attend the Annual Conference of the Geological Society of America), I was surprised by this little calculator that popped up to inform me of the environmental impact of my decision and route.
Now, not all transit systems are equivalent. Too many of them rely on high-emissions, even environmentally hazardous, vehicles. But at the very least, they are no worse than a passenger vehicle, and they are always better than passenger traffic because of the volume of passengers in a single vehicle. So check out your local transit system and see if they're already impressing you with a similar calculator. If they're not, then encourage them to do so! It's good for the public, it's good for business, and it's good for the environment.