<Lecture
Summary>
Professor Morikawa introduced the "P-DRGS (Probe-Dynamic
Route Guidance System) Consortium", including an overview
and planning. For my lecture, I will discuss the technical
elements involved in developing P-DRGS.
A
diverse range of technical elements is currently under
development. From among them, I would like to introduce
"DB (database) information accumulation technologies,"
"technologies for updating the DB based on real-time data,"
"road and rail route search technologies" for predicting
trip time, "trip time correction using real-time rainfall
information," for integrating weather information into
data, and finally "developing vehicle-mounted devices"
for evaluating vehicle-mounted systems.
The DB information
accumulation technology used to predict trip times employed probe data from
approximately 1,500 taxis operating in the city of Nagoya over a 10-month period
in 2002 and 2003. The information was made into a database for expressing the
average trip time in time units per link. A DB utilizing probe data was also
assembled for showing the average trip time per effective link. This was formed
using technologies for "screening out abnormal data," "setting optimal time
widths" and "supplementing information with VICS (Vehicle Information Communications
Systems) data".
There are two
types of DB update technology that use real-time data. One type is technology
that can "update with real-time probe data". This technology utilizes an autoregressive
model to make predictions and update the data accumulated in the DB. The other
technology utilizes JARTIC (Japan Road Traffic Information Center) data, and
updates information accumulated in the DB using traffic congestion/jam information
and other regulatory data.
A link cost update technology for searching out the optimal route was developed
from among the road and rail path search technologies available. The route
search is calculated while taking into account the lateral split cost on the
link. Results revealed cases in which the shortest route was not the same when
the lateral split cost was considered. A route search technique was also developed
for use with train commutation. This approach uses the same algorithm as when
making a road network search.
Integrating
weather information and analyzing the difference between trip times during
fair weather and trip times when it is raining revealed that trips when it
is raining are approximately 5-7% longer than those taken at the time of fair
weather. Other factors such as the rainfall intensity and time segments were
also used in the analysis. A system for correcting the trip time using real-time
rainfall information is also being configured.
The final stage
concept of the P-DRGS consortium is aimed at delegating functions so that base
information, such as a link cost table, is drawn up at the center and sent
to the vehicle-mounted system in real time, where the route to be taken by
the vehicle is created. However, the experimental system is configured so that
vehicle-mounted processing is also performed at the center.
The
P-DRGS center located in the Morikawa Research Lab of Nagoya
University and My personal computer (PRONAVI user terminal
which simulates a vehicle-mounted system) gives a real-time
demonstration of the system via connections over the Internet. The information
area is a two-dimensional mesh made up of a 25-grid area centered on the
city of Nagoya, and the road network consists of 149,042
links and 57,827 nodes. This demonstration can compare
access routes from a parking lot in Nagoya to the Aichi
Expo when the expressway or ordinary roads. It can also
compare routes when using public transportation systems
such as the subway.
Future prospective
ITS features include incorporating the above-mentioned technical elements under
development into the system, developing new technologies for accumulating probe
data, improving trip time prediction accuracy, combining our systems with eco-points
and park-and-ride services, etc.