The RAND Corporation is out with a detailed analysis of the potential market for car sharing as well as the theoretical greenhouse gas reductions. Tanya Snyder breaks down the figures on the DC Streets Blog, showing that if policies supported car sharing, the market could reach 7.5 millions users compared to the 560,000 current users. RAND puts the outer market limit as a bit over 20 million users, which while still relatively small would make a major impact on traffic and congestion since car sharing reduces the amount of vehicles on the road and frees up parking. And the major impacts on congestion come from that 10 percent of cars on the margin pushing problems over the tipping point. Not to mention a 10 or 20 times increase in market size would be just fine for Zipcar and newcomer Hertz. In terms of GHGs, at a market size of 7.5 million users, car sharing would eliminate 6.7 million metric tons of emissions, still less than 1 percent of the total GHGs from the entire U.S. light duty fleet. Still a very small incremental reduction, and further proof that if folks still want the right to consume enough energy to haul two tons twenty miles every day (what you do if you drive), we’ll have to pair electric cars with renewable sources of power.