I am looking at a 2007 project for enviormental savings as folllows:

Car pooling
How do I measure thr impact such as greenhouse emmisions and gas savings?
Gas reduction I can measure but what other measures are there and how do I measure?

Is this for ISO 14001?

If so, it's interesting to include carpooling as a company's environmental impact.

Effects of actions are generally compared in a before/after trend.

Employees can directly report their gas savings into a pool. Emissions are harder, but can be estimated with a spreadsheet into which those carpoolers' savings are fed. This site (http://www.conservationfund.org/?article=3142)gives formulas to use:

Gas mileage data are from the U.S. Environmental Protection Agency and the U.S. Energy Information Administration. The average U.S. vehicle is driven 11,700 miles per year according to the Energy Information Administration.

Gallons are converted to CO2 using 25.3371 lbs CO2/gallon gas - 19.2898 lbs of CO2/gallon in direct emissions and 6.0473 lbs of CO2/gallon in upstream CO2 emissions - from the Greenhouse Gases, Regulated Emissions, and Energy Use in Transportation (GREET) model.

Please see this site (http://epa.gov/climatechange/emissions/ind_calculator.html)for a handy calculator. The site also has a link to a spreadsheet, in which the formulas can be seen and used in your own spreadsheet to add up and chart the group's impact over a period of time.