Development and Evaluation of In-vehicle Signing System Utilizing RFID tags as Digital Traffic Signs

Abstract

Tome Public Works and Construction Office, Miyagi Prefectural Government *1 (150-5 Nishi-sanuma, Hasama-cho, Tome, Miyagi, 987-0511, +81(220)22-2494 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.

Full text

International Journal of ITS Research, Vol. 4, No.1, December 2006
Development and Evaluation of In-vehicle Signing System
Utilizing RFID tags as Digital Traffic Signs
Yoshimichi Sato*1 Koji Makanae*2
Tome Public Works and Construction Office, Miyagi Prefectural Government *1
(150-5 Nishi-sanuma, Hasama-cho, Tome, Miyagi, 987-0511, +81(220)22-2494, sato-yo436@pref.miyagi.jp)
Department of Spatial Design and Information Systems, Miyagi University*2
(1 Gakuen, Taiwa, Miyagi, 981-3298, +81(22)377-8368, makanae@myu.ac.jp)
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.
Keywords: in-vehicle signing system, RFID, traffic sign
1. 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 Commu-
nications).
Under the circumstances, an attempt is made in this
study to apply RFID (Radio Frequency Identification) as
digital traffic signing replacing existing signs. Efforts are
now being made to seek applications for RFID tags as
the next generation of tag systems. Wider use of RFID
tags is now being accelerated. As applications of RFID
to digital traffic signing, some systems have been
developed for pedestrians [2]. For vehicle users, however,
no reports have yet been made on specific studies for
practical implementation of the tag system although the
possibility of using the system has been suggested. In
this study, an in-vehicle signing system is built and
assessed that uses general-purpose RFID tags as digital
traffic signs and communications between the road
surface and vehicle equipment. Then, the serviceability
of the system is identified.
2. Existing studies and the significance of
this study
In relation to in-vehicle presentation of traffic signs,
studies have been made of traffic signing systems using
DSRC and systems using digital road data. Systems in
the first category help the driver safely maneuver
through a curve by providing such messages to the driver
as "No overspeeding" and "Slow down" before the
vehicle enters the curve via 5.8-GHz short range
communications [3]. The latter systems extract positions
of traffic signs from an image of a road scene,
incorporate the position data into digital road data and
present traffic sign data with geographic information
using a GPS-based car navigation system [4]. Studies
have also being carried out on image processing in
which traffic signs are automatically detected and
recognized from image data. Kohashi et al. [5] have
made possible the recognition of traffic signs and signals
based on the data on their color and shape by eliminating
from the image other types of data that are not to be
recognized. Makanae and Kanno [6] have proposed
traffic signs designed to be recognized by computer and
evaluated their visibility.
Problems involved in the above systems are described
below. Systems using DSRC offer reliable commu-
nications but involve problems of cost and space if they
are to be installed on ordinary roads. GPS-based systems
do not provide for dynamic update of signs on the map
and provide less accurate position data in places where
GPS is unavailable such as tunnels and other structures.
Image processing systems are inapplicable where
visibility is poor because of the weather or the visibility
ahead of the vehicle is deteriorated by large vehicles.
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Development and Evaluation of In-vehicle Signing System Utilizing RFID tags as Digital Traffic Signs
To solve the above problems, a system is built and
verified in this study for presenting signing in the vehicle
through communications between road and vehicle
equipment using general-purpose RFID tags as digital
traffic signs. RFID offers communications only in a
limited area because it uses feeble radio waves. RFID
can provide information in specified areas, so it can
identify positions highly accurately. Electromagnetic
passive RFID tags require no power source, are highly
resistant to dust or obstacles and of very small size. Tags
are so cheap that they can be installed in large numbers.
RFID tags are therefore free from the problems related to
the cost and location of installation of DSRC, accuracy
of position data provided by GPS or visibility where
image processing is adopted.
3. System outline
3.1. Equipment used
In this study, a system is built to read traffic sign and
signal data stored in RFID tags placed on the pavement
by an in-vehicle RFID reader and to present the data as
voice and image data on an in-vehicle terminal screen
(Figure 1).
The system uses the following tools.
- RFID tag: Tag-it HF-I of Texas Instruments Incorporated
- Transponder inlay rectangle 76 mm x 45 mm
- Identifier: 64 bit
- User memory: 2048 bit, 32 bits/block
- Applicable standards: ISO/IEC 15693
- Frequency of operation: 13.56 MHz
- Number of times of writing: 100,000 times
- Data retention period: 10 years
- RFID reader: FMR100-A of FEIG ELECTRONIC
This study assumes the use of electromagnetic passive
tags, which have a shorter communications range than
active tags. The tags employed in this study have a
maximum communications range of 40 cm. A benefit of
using feeble radio waves is more accurate positioning. It
should be made sure that the antenna of the reader is
close to the tag.
3.2. 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.
3.3. 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.
Figure 4 shows how data are stored in tags. The
preliminary tag (Tag-0) in (i) stores data on traffic signs
50
50
RFID ta g RFID re ader
(antenna)
50
speed limit
50km/h
sign
display
50
Figure 1. The in-vehicle signing system utilizing Figure 2. Installation of RFID tags
RFID
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International Journal of ITS Research, Vol. 4, No.1, December 2006
‘3290’ and ‘4072’. No data are displayed on the terminal
screen. (ii) is the start tag (Tag-1) containing data on
traffic signs ‘3290’ and’4072’. When it receives the data
on the signs, the terminal starts displaying information.
(iii) is the preliminary tag (Tag-0) for ‘3230’, another
traffic sign. When data in the end tag (Tag-2) for ‘4072’
contained in (iv) and data in the start tag (Tag-0) for
‘3230’ are read, different data are displayed on the
terminal screen.
3.4. In-vehicle signing system
A flowchart of the in-vehicle signing system loaded on
the in-vehicle terminal is shown in Figure 5.
When a tag is detected, tag data are read to determine
the type of the tag. If the tag is found to be Tag-0
(preliminary tag), the traffic sign identifier is stored in a
preliminary memory space. If Tag-1 (start tag) is
detected, the traffic sign with the same identifier is taken
from the preliminary memory space and data on the sign
(image and voice data) are extracted for presentation.
Data displayed in a presentation memory space are
stored. If Tag-2 is detected, display of data on the traffic
sign is terminated as long as a traffic sign with the same
identifier is in the presentation memory space.
A sample display screen is given in Figure 6. The
screen was designed simply so that it could be used also
by the car navigation system. Speed data are displayed in
the upper right and other data on the left side of the
screen.
4. System evaluation tests
4.1. Field road test
To evaluate the effectiveness of the system, a test was
conducted on a road in the premises of Miyagi
University. A road from the entrance of the university to
a northern parking space was used for testing. Eleven
traffic signs were installed in the section (Figure 7).
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Figure 3. Format of data storage in tags
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Figure 4. An example of data storage in tags
Start
Initialize
Search RFID tags
Detected?
Read information from
the tag
No
Yes
Check
the type of tag
Type of tag
Reset memory
Store
the sign ID
in memory
Start display
of the sign
0
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N.G.
Terminate display
1
2
Figure 5. Flowchart of the signing system
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type signID
type signID numerical data
Curve ahead
Speed Lim
t
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Development and Evaluation of In-vehicle Signing System Utilizing RFID tags as Digital Traffic Signs
The tags used in the test had a maximum
communications range of 40 cm. A 30-cm-wide antenna
was installed on the vehicle at a height of 15 cm from the
ground surface (Figure 8 (a)). Three tags containing the
same data were placed at spacing of 30 cm in cross
section of a lane so that they could be detected even if
the vehicle traveled off the centerline of the lane (Figure
8 (b)). A total of 57 tags were installed at 19 positions.
Each tag was sandwiched between 0.6-mm-thick acrylic
plates and fixed on the surface with sealing tape.
The vehicle traveled at a speed of approximately 20
km/hr. The system functioned properly. Data stored in all
of the tags installed could be recognized and displayed
(Figure 8 (c)).
4.2. 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.
Table 1 lists questionnaire research results. When the
in-vehicle signing system was adopted, the rating
exceeded 3.8 on average on a scale of 1 to 5 in all items
including the recognition and understanding of traffic
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Figure 8. Scenes of the experimentation
Figure 6. A screenshot of the signing system
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・: Sign tag
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Parking space
for motorbikes
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International Journal of ITS Research, Vol. 4, No.1, December 2006
sign. The system was thus highly appreciated. Cases
were ranked in the order of serviceability of the system.
Case (iv) providing visual and vocal data won the
highest rank (mean ranking: 1.6) followed by (iii)
providing vocal data only (mean ranking 2.3)(ii) with
visual data only (mean ranking: 2.5) and (i) without the
system (mean ranking: 3.7). As a result of the research, it
was found that the respondents preferred in-vehicle
display of traffic signs and vocal provision of
information.
5. Serviceability and problems of in-vehicle
signing system
As a result of the field and laboratory tests (Chapter 4),
in-vehicle signing system using RFID tags as digital
traffic signs was regarded highly effective and image and
voice data provided in-vehicle were found to be easy to
understand. Thus, the system was found necessary. Then,
it was revealed that in-vehicle data display equipment
was effective for supporting drivers and that the
application of RFID could be an element technology for
implementing the system.
The RFID signing system is lower in cost than the past
vehicle to road communication systems such as DSRC,
although it cannot support dynamic communication.
Moreover, RFID tags can provide their position more
accurately than GPS systems under various
environments. Therefore, it is expected that a more
robust signing system can be achieved utilizing RFID
system.
In this study, RFID tests were conducted on a vehicle
traveling at a low speed in a road in the premises of the
university. In the future, system serviceability should be
evaluated under real conditions through testing on
highways. The following problems have yet to be solved.
(1) System evaluation and measures required for
vehicles traveling at high speeds
In this study, tests were conducted using a vehicle
running at a low speed. In the future, tests will be
required in relation to the recognition of traffic signs by
speeding vehicles. When a vehicle is traveling at a high
speed, equipment used in this study is unlikely to read
data sufficiently because of short transmit distance
(max.40cm).Applying RFID tags in UHF bandwidth
range (such as 900 MHz bandwidth range) with a
communications range of two to three meters should be
considered. The experiments in this study were
conducted under the condition where few cars existed.
However, there is a possibility that errors of recognition
are caused due to high-speed traffic, instability behavior
of vehicles or the damage of tag etc. under real traffic
conditions. It is required to add the function to check
recognition, and to develop the system that consider
fail-safe.
(2) Positions of tags
In this study, three types of tags were installed so that
a check could be made to prevent wrong information
from being displayed and to ensure the recognition of
right information. If data only in one tag cannot be read,
no corresponding traffic sign is displayed. In the future,
positions of tags should be examined to ensure in-vehicle
information display.
(3) Methods of installing tags
In the tests in this study, tags protected with acrylic
plates were attached direct to road surface. How to
install tags on actual highways is important. If impact is
considered, burying tags under the pavement is
appropriate. Detailed research and study should be made
as to how to bury tags under actual conditions, the
effects of radio attenuation due to the installation of tags
in the ground and the effects of weather and impact
loads.
(4) Information in tags
A RFID tag used in this study can store 2048-bit data
(64 signs by the data format in this study). The volume
of information in the road sign is limited by the
conventional signing system based on human recognition.
Using RFID signing systems, more precise information
for traffic control are able to be stored in the tag, and to
be notified to drivers more accurately. In the future, data
to be stored in tags should be examined.
(5)Antenna mounting method
How the reader antenna is mounted on the vehicle
becomes a problem in practical use. In the experiment, a
reader antenna was mounted on the rear end of the
Table 1. Questionnaire research results
Figure 9. The system
for a laboratory test
(
1 to 5 scale 5:YES----1:NO
)
(
ⅰ
)
not in use
(
ⅱ
)
dis
p
la
y
(
ⅲ
)
voices
(
ⅳ
)
dis
p
la
y
voices
1.Can you watch the display or display hear
the voices? N/A 4.6 4.1 4.7
2.Can you understand information? N/A 5.0 4.5 4.6
3.Is this system more effective than
convertional si
g
nin
g
s
y
stem? N/A 4.4 4.1 4.6
3.Is this system useful for senior drivers? N/A 3.8 4.3 4.5
(
Rankin
g)
Ranking of easiness for driving? 3.7 2.5 2.3 1.6
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Development and Evaluation of In-vehicle Signing System Utilizing RFID tags as Digital Traffic Signs
vehicle, however, the most suitable antenna and
mounting method correspond to the radio frequency and
power must be examined.
(6)Presentation method to drivers
The result of the experiments shows that the
presentation method using voices with the display is the
best way to present the information of signs. However, a
visual presentation often becomes the trouble for the
maneuvering due to movements of the glance and the
focus. It is necessary to examine the method of the
display such as windshield display etc., which enables a
driver to receive information more naturally.
(7) Interconnection with advanced cruise-assist highway
system (AHS)
Data obtained by the in-vehicle signing system have
great potential for advanced application through
interconnection with automatic control systems such as
advanced cruise-assist highway system and automated
highway system. Future studies will be required.
6. 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.
References
[1] U.S.Department of Transportation:
http://www.its.dot.gov/arch/, 2005.
[2] Uchida, T., “Pedestrian Navigation Systems in CBD:A case of
Mido-suji,Osaka,Japan”, Proc. 2nd ITS Symposium 2003, pp.53-58.
[3 ] Oki, Y., Yamada, F., Seki, Y., Mizutani, H., Makino,H. “Actual Road
Verification of AHS Support System for Prevention Of Vehicle
Overshooting on Curves”, Proc. 2nd ITS Symposium 2003,
pp.247-252.
[4] Uchimura, K., Tominaga, H., Nakamura, K., Wakisaka, S., Arita, H.
“Adding a Route Guidance Sign to Digital Road Map”，
Proc. 1st ITS
Symposium 2002, pp.25-30.
[5] Kohashi, Y., Ishikawa, N., Nakajima,M. “Automatic Recognition of
Road signs and Traffic signs”, Proc. 1st ITS Symposium 2002,
pp.321-326.
[6] Makanae, K., Kanno, A., “Proposal of the Signing System
Utilizing Image Recognition”, Proc. 1st ITS Symposium 2002,
pp.137-142.
Yoshimichi Sato is an administrative
officer of Tome Public Works and
Construction Office, Miyagi prefectural
government. He received the Bachelor of
Spatial Design and Information Systems
(Miyagi University).
Koji Makanae is a professor of School
of Project Design, Miyagi University.
He received the Ph.D. in Information
Sciences from Tohoku University in
1998. His major interests are spatial
informatics and its application.
•Received date: May 29 2006
•Received in revised form: November 9 2006
•Accepted date: November 10 2006
•Editor: Masataka Kagesawa
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