) minutes, where (< s) is
the guidance resolution. In other words, guidance is time dependent
within each step size s. This resolution, , defines the length of time intervals considered in calculation of
link and path times (see Figures 4-2 and 4-3). Link and path travel times
for vehicles that depart at a particular time are represented by
piecewise linear functions. For example, in Figure 4-3 the expected travel time
for vehicles entering the link during 7:00-7:10 is interpolated based
on the predicted average travel
times in three time intervals from 6:50 to 7:20. The smaller the
time intervals considered in calculation of link and path times, the
more dynamic the generated guidance might be. However, smaller time
intervals require more elaborate input data and computational power.
Moreover, using smaller time intervals also introduces the risk of
instability. The developed TMS module allows the user to experiment
with different values for this parameter, and, therefore, facilitates
the development of appropriate ATIS design based on the network
structure, quality of the surveillance system, and available
computational resources.
Figure 4-3: Piecewise linear time-variant travel
time