With ver. 8.0, the options are limited to fuel consumption & emission models that confine their input to quantities evaluated on a link basis or node-by-node basis (e.g., average speed vs. freeflow speed, number of stops along the link, delay, stopped-delay, amount of time spent below a given speed, etc.). Implementations of two of these models are available on the Downloads page
http://www.tru-traffic.com/downloads.htm -- scroll down to the link titled "FuelConsumption&Emissions_mph.URC". Follow the instructions there for installing. If you have a different model in this category, you may enter its formulas yourself as user-defined columns in the TT&D report.
Ver. 9.0 enables support for the much more accurate and comprehensive "modal" models (e.g., CMEM
http://www.cert.ucr.edu/cmem/), which consider the second-by-second state of the vehicle (e.g., instantaneous speed, amount of acceleration or braking, etc.) during the run. These are also available on the Downloads page -- scroll down as needed to the link "Emissions using CMEM for Vehicle Category 4.URC" -- but they would require upgrading to ver. 9.0. As before, follow the instructions there for installing. And if you have a different model in this category, you may likewise enter its formulas yourself as user-defined columns in the TT&D report.
If anyone reading this can send me information about other models in either of the above categories, I'll try to use the formulas to create user-defined columns and post them on the Downloads page so everyone has easier access to them.
Regards.
Greg