14-01-2013, 04:15 PM
Development and Evaluation of In-vehicle Signing System Utilizing RFID tags as Digital Traffic Signs
Development and Evaluation.pdf (Size: 196.92 KB / Downloads: 45)
Abstract
Vehicle drivers are requested to collect dynamic visual information on such matters as other vehicles and traffic signals,
and static visual information including traffic signs, and to maneuver the vehicle accordingly. However, traffic signs and
other static visual information are more likely to be overlooked than dynamic visual information during maneuver. In
this study, an in-vehicle signing system was built and assessed that uses general-purpose RFID tags as digital traffic
signs, and a field test was conducted using tags installed on a road to verify whether the system worked effectively or
not. A laboratory test was also carried out using a video of vehicle travel to have subjects experience maneuver. Then, it
was found that providing visual and vocal information in the vehicle was effective.
Introduction
Traffic signs visually provide drivers with regulatory,
warning and guide information. Vehicle drivers are
requested to collect dynamic visual information on such
matters as other vehicles and traffic signals, and static
visual information including traffic signs, and to
maneuver the vehicle accordingly. Actually, however,
traffic signs and other static visual information are more
likely to be overlooked than dynamic visual information
during maneuver. As a solution to the problem,
in-vehicle signing systems that are capable of displaying
signing on a terminal in the vehicle are expected to
provide an effective support. The system has been
designated as one of the ITS market packages in the
National ITS Architecture of the United States [1]. In
Japan, however, the serviceability of the system has yet
to win sufficient social recognition although several
experiments have been conducted using image
processing or DSRC (Dedicated Short Range Communications).
Positions of tags
If information is displayed based on the data stored in
only one tag in a lane, no direction of the vehicle can be
identified. As a result, in the case where the vehicle uses
the lane of opposing traffic to pass another vehicle or get
around an obstacle, or where the vehicle travels in a
narrow undivided road, data stored in tags on the
pavement of the lane of opposing traffic are collected
although such data are unnecessary for the travel of the
vehicle. In this study, therefore, Tag-0 (preliminary tag),
-1 (start tag) and -2 (end tag) are defined to check the
recognition of signs. The three tags are located in
succession on a lane (Figure 2). Tag-0 provides the
existence of the sign forward of the lane, and has the role
to check the traveling direction of the vehicle and the
recognized data. Data are displayed on the assumption
that they are obtained from Tag-0, and then from Tag-1.
When data have been obtained from Tag-2, data display
is terminated. Tags-1 and -2 indicate the start and end of
a section, respectively. This approach makes the system
applicable also to a narrow undivided road carrying
bidirectional traffic.
Format of data storage in tags
The type of tag (0, 1 or 2) is stored in the first digit of
the RFID tag followed by the traffic sign identifier
(Figure 3). Numerical data such as the speed limit and
weight limit are stored in subsequent digits, if any.
Traffic sign data are stored in 32-bit blocks. Tag-it used
in this study can accommodate a maximum of 64 traffic
signs per tag. In the test, however, data on a maximum of
four traffic signs were stored in each tag to reduce the
time required for reading data
Evaluation of system serviceability in
laboratory
In order to evaluate the effectiveness of the in-vehicle
signing system, a laboratory test was conducted
simulating driving experience using a video recording of
vehicle travel on an ordinary road.
To reproduce the use of the in-vehicle signing system,
a video of vehicle travel taken from the driver's
viewpoint was replayed on the video monitor. A personal
computer was installed in front of the monitor to display
traffic sign data in synchrony with the video (Figure 9).
The subjects were instructed to sit in front of the
monitor and watch the video as if driving the vehicle.
The test was conducted to have the subjects experience
cases where (i) the system was not in use, (ii) data were
only displayed on the screen, (iii) data were provided
only vocally and (iv) both visual and vocal data were
disseminated. In cases (ii) through (iv) where the system
was employed, the subjects were requested to rate the
system on a 1-to-5 scale in such terms as the recognition
and understanding of traffic sign data. The subjects were
also instructed to rank cases (i) through (iv). 11 licensed
drivers, 9 men and 2 women, of an average age of 22.3
years participated in the test as subjects.
Closing remark
In this study, an in-vehicle signing system was built
and assessed that uses general-purpose RFID tags as
digital traffic signs, and a field test was conducted using
tags installed on a road to verify whether the system
worked effectively or not. A laboratory test was also
carried out using a video of vehicle travel to have
subjects experience maneuver. Then, it was found that
providing visual and vocal information in the vehicle
was effective.
Matters that have yet to be examined include (i)
system evaluation and measures required for vehicles
traveling at high speeds, (ii) positions of tags, (iii) how
to install tags on roads, (iv)information in tags, (v)
antenna mounting method, (vi) presentation method to
drivers and (iv) interconnection with the cruise-assist
system.
Based on the results of this study, the system should
be enhanced for practical application and a social system
should be examined for replacing existing traffic signs
with digital signs.