The Google Maps API approach accounts for road
congestion.
The road network data used in ArcGIS 10 contain
the speed limit for each road segment, which
is assumed to be the travel speed by the Network
Analyst module. For illustration, we choose the
route from the GSRI Avenue (at geographiccoordinates 30.363512, −91.150997) to the Earl
K. Long Medical Center (at geographic coordinates
30.5783, −90.9942) as an example. Figure
6(a) shows the path by ArcGIS on the StreetMap,
and Figure 6(b) shows the path on the Google
Maps. The two routes are similar. However, the
travel time is 30 minutes by ArcGIS, but 40 minutes
by Google. The difference is significant. A
close examination of travel speed on each road segment
shows that the travel speeds on roads around
the LSU and the downtown area were much slower
than the posted speed limits.