AirCRED

Calculating Ozone Emission Reduction Credits for Clean Cities Vehicles

AirCRED, written in Visual.net, presents screens to help you input data and then outputs information based on your input. AirCRED allows you to select options by clicking on buttons from each screen and to enter your own data. AirCRED will lead you through a sequence of data entry as you use your mouse and keyboard. You can print a copy of every input and output (results) screen. You can also return to any data input screen if you want to change the parameter values. AirCRED is user-friendly — each screen tells you what to do in a straightforward manner, and a clearly understandable result is provided at the end of the process. AirCRED is not rocket science — it's a handy tool for busy people.

The current version of AirCRED (version 4.2, July 26, 2006) allows you to save data entered in prior sessions by creating a unique username to log into the site on return visits. You can retrieve the inputs of a prior session by choosing the appropriate season and Clean City, so you can save data for more than one season and city combination.

AirCRED is based on the U.S. Environmental Protection Agency's (EPA's) MOBILE model combined with emission test certification data for new original-equipment-manufacturer alternative fuel vehicles (AFVs) and their gasoline- or diesel-fueled counterparts. It starts with the MOBILE-computed emission factor (by vehicle type) appropriate to (a) the midsummer ozone season or (b) midwinter carbon monoxide conditions. The "clean gap" between AFV and gasoline or diesel counterpart emissions of NMHC, carbon monoxide, and nitrogen oxide, according to season, determines the magnitude of the net gram per mile credit that can be taken for AFVs in each Clean City, relative to MOBILE's emission rates.

• For light-duty vehicles, credit is based on the entire chassis dynamometer-based Federal Test Procedure, including supplemental tests.
• For heavy-duty diesel vehicles (transit and school buses and medium to heavy trucks operating on natural gas), credit derives from engine dynamometer certification data.

AirCRED reports results in tons and pounds per day. You can then multiply this value by the number of days that the AFV fleet operates over your entire ozone or carbon monoxide season to take the appropriate annual credit. (A multiplier equal to the number of days in the year is inappropriate because the emission factors applied reflect specific seasonal conditions.)