Vehicles of the same make and model can be certified to multiple emissions levels, in order to meet emissions requirements in different parts of the country. The tool uses a single emissions standard for the default data that represents the most common configuration for fleet applications. If you chose not to use the default data vehicles, you will need to choose an emissions standard. The states of CA, MA, ME, NY and VT have vehicles available meeting the CA stricter standards. Contiguous states including AZ, CT, NH, NJ, NV, OR, PA and RI may also sell such vehicles. More on what the emission standards mean can be found at http://www.dieselnet.com/standards/us/light.html.
More on the emission standards available for various vehicles is available at http://www.fueleconomy.gov/feg/findacar.htm.