Information Technology Reference
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Many reports have indicated that the total cost paid for traffic congestion is
tremendous. For example, Schrank and Lomax [7] investigated the traffic
congestion problem in 75 U.S. urban areas. The 75 areas used in the analysis
include a range of populations from 100,000 to 17 million for the years from
1982 to 2001. They found that the total congestion cost for the 75 areas in 2001
came to $69.5 billion, which was the value of 3.5 billion hours of delay and
5.7 billion gallons of excess fuel consumed.
Traditional ways to alleviate traffic congestion problems are to construct
new roads or widen existing roads. Unfortunately, both ways are very expen-
sive solutions. With rapid advances in wireless communication networks
and GPS-enabled devises (such as smart phones, PDAs, or car PCs), it is now
feasible to use vehicle navigation systems, a more cost effective solution. In
the past, many studies have shown that vehicle navigation systems can effec-
tively alleviate traffic congestion problems. For instance, Bose and Ioannou
showed that automatically guided vehicles can increase the throughput of
roadways to double that of manually driven vehicles [1].
Vehicle navigation systems can be classified into two categories: static rout-
ing systems and dynamic routing systems. In static routing systems [11,12],
vehicle navigation systems find the shortest path to guide a vehicle from its
origin to its destination without considering the real-time traffic conditions
on different roads. In implementation, some modifications may be made to
change the weights of some roads. For example, some roads are assigned
higher or lower weights according to the driver's preference and other factors
(such as rush hours or nonrush hours). In dynamic routing systems [2,10,14],
the real-time traffic information of different roads will be taken into account
when deciding the quickest path. For this reason, we also refer to dynamic
vehicle navigation systems as real-time navigation systems. In addition to
this type of classification (i.e., static versus dynamic), other viewpoints can
be used to classify different vehicle navigation systems. A comprehensive
study that classifies different vehicle navigation systems from several view-
points can be found in Schmitt and Jula [6].
Real-time vehicle navigation systems consist of the following main
components: (1) GPS receiver, (2) wireless communication network interface,
(3) digital road map, (4) route guidance algorithm, and (5) real-time traffic
information collecting algorithm. Real-time navigation systems perform three
main functions: (1) collecting local traffic information from different roads, (2)
merging the local traffic information to generate wide-area routing informa-
tion (i.e., route guidance information), and (3) delivering the routing informa-
tion to the vehicles that need navigation. According to the routing information,
guided vehicles can find quicker paths that bypass congested areas to save
the driving time and alleviate traffic congestion problems.
To collect real-time traffic information from different roads, we need a
proper network technology. However, existing network technologies, such
as GPRS/3G and WiFi, are not specially designed to deliver vehicular traf-
fic information. Over the past few years, a new network technology, called
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