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interest to many groups of people such as transportation engineers, traffic
administrators and geographers. In geographical information science,
many researchers have paid much attention to the importance of individual
roads for various applications such as pedestrians or vehicle movement
analysis (Hillier and Hanson 1984; Hillier et al. 1993) and road network
generalization (Mackaness and Beard 1993; Mackaness 1995; Thomson
and Richardson 1995).
Road network generalization which is caused by scale change aims to ab-
stract the representation of road networks by reducing details. When the
map scale is reduced, the available space on map to represent the same
amount of information is also reduced. Therefore, it's essential to deter-
mine which roads are still needed to be represented on map. A series of
operators, such as selective omission, simplification, and displacement (Li
2006) may be involved. Among these operators, selective omission which
is defined as a processing of selecting more important roads is one of the
most essential ones.
There have been several approaches proposed for the selective omission
operator. Due to the fact that a road network in the database is always
viewed as consisting of a number of road intersections and road segments,
it is natural to implement selective omission by analyzing the importance
of road intersections (Mackaness and Machechnie 1999) or road segments
(Mackaness and Beard 1993; Mackaness 1995; Thomson and Richardson
1995; Kreveld and Peschier 1998). However, a long road may be repre-
sented by many road segments. This may constitute a problem for some
spatial analysis because the results obtained from analysis of the whole
road could be different from those obtained from segment-based analysis.
That is, sometimes, to re-build individual roads in the road database is very
desirable. Thomson and Richardson (1999) adopted the concept of
“stroke” which was first defined as “a set of one or more arcs in a non-
branching, connected chain”. This concept makes selective omission based
on the importance of individual roads become possible. More importantly,
in the road network, the property of an individual road seems more sensi-
ble than the one of a road segment. For instance, normally a long road is
more important than a short one, but it is hard to say a longer road segment
is more important.
The importance of individual road/stroke may be determined according to
different properties. Chaudhry and Mackaness (2001) proposed stroke
length. All the strokes were ranked based on their lengths. Then the road
network could be abstracted by simply selecting long strokes. Zhang
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