Figure 10(a) and (b) shows the accessibility Z scores by
the ArcGIS and Google methods, respectively. Darker colors
correspond to lower and negative Z scores, that is, average
travel time to hospitals below the areawide mean, and
better accessibility. The accessibility is the highest around
the Essen medical campus with several hospitals (southeast
of the city center) and declines outwards. The patterns are
generally consistent on the two maps. However, there are
differences, particularly in the middle-range-distance areas
from the city center. Figure 11 maps the difference (i.e., Z
score by Google – Z score by ArcGIS). Cold colors correspond
to negative values (lower Z scores by Google than
by ArcGIS) and indicate that the accessibility in the area
based on the Google time is better than that suggested by
the ArcGIS time. Warm colors indicate otherwise. From
Figure 10, most areas toward northeast are in cold colors
and thus indicate that Google time tends to suggest better
accessibility than ArcGIS time does. The opposite can be
said on the southwest corner