Traffic assignment results (Figure 3) indicate the amount of travel to be expected on each link in
the network at some future date with a given transportation system. Levels of congestion travel
times speed of travel and vehicle miles of travel are direct outputs from the modeling process.
Link traffic volumes are also used to determine other effects of travel for plan evaluation. Some of
the key effects are accidents, and estimates of air pollution emissions. Each of these effects needs
to be estimated through further calculations. Typically these are done by applying accident or
emission rates by highway type and by speed. Assumptions need to be made of the speed
characteristics of travel for non-peak hours of the day and for variation in travel by time of the
year