The Development of AHS and Element Technologies :
Proving Tests and Field Operation Tests
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Yoshio Kasuga Manager Advanced Cruise-Assist Highway System Research Association |
The Element Technologies Development Department has formed the following five Research Teams (RT) that have been conducting research under their respective RT leaders on two common tasks: (1) The verification and improvement of functions directed toward the practical application of element technologies, and (2) the creation of technical reference materials that organize the results of the past five years of research.
| Research Team (RT) | Leader |
| Road condition detection systems (K1) | Inaba, Toshiba Co. |
| Road surface condition detection systems (K2) | Kuno, Denso Co. |
| Cruise assist information systems (K3) | Nakajima, Hitachi, Ltd |
| Vehicle position information systems (K4) | Suzuki, Mitsubishi Electric Co. |
| Information telecommunications systems (K5) | Inoue, Oki Electric Industry Co. Ltd |
1. Road Condition Detection Systems (K1)
The objective of this research is to develop sensors for detection of moving
vehicles and obstacles on the road. The research from 1996 to 1999 began with
surveys of the performance of existing sensors and proceeded gradually with
research and development. In 2000, this team operated the sensors for proving
tests at the National Institute for Land and Infrastructure Management and evaluated
the detection performance and reliability of sensors in heavy traffic environments.
With the cooperation of the Japan Highway Public Corporation (JH), the team
installed field operation test equipment in the vicinity of the Ashigara Service
Area on the Tomei Expressway. There they carried out functional verification
and improvement of sensor performance during the winter. As shown in Fig. 1,
visible-light camera, infrared camera, and millimeter-wave radar sensors were
installed on the downhill lanes near the Tomei Expressway Ashigara Service Area,
and a comparative study was made of the measurement results from the various
sensors. Reference values were obtained from loop coil measurements. Data collection
has been underway on a 24-hour basis since November of last year. Performance
evaluation for the winter season, which lasted until March, yielded results
showing that the infrared sensor had superior overall performance, followed
by the millimeter-wave sensor and then the visible-light sensor. Additional
testing of the laser radar pedestrian detection sensor was conducted at the
Ishikari Blizzard Test Station in Hokkaido. This confirmed that the sensor was
able to detect pedestrians in a crosswalk on a six-lane road with almost 100%
probability when visibility was at 200 m or more.
| Fig. 1. Layout of Road Sensors at Ashigara Service Area |
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2. Road Surface Condition Detection Systems (K2)
The objective of this research is to develop sensors that will improve safety
by providing vehicles with advance information about road surface conditions
such as dry, wet, snow-covered, and frozen surface. In 2000, the team conducted
field operation tests at Nakayama Pass in Hokkaido and in the vicinity of the
Ibuki Parking Area on the Meishin Expressway of JH. Functional verification
and improvements were carried out as a result. These two locations were selected
primarily because they are in cold climates with snow cover, and Fig. 2 shows
the test conditions. Nakayama Pass has traffic volume of 10,000 cars daily,
and has a very harsh environment, with a mean atmospheric temperature that is
several degrees below freezing during the winter, and three months or more of
snowfall. The vicinity of Ibuki Parking Area has a heavy traffic volume of 50,000
cars daily, and it is in a district where road management must pay close attention
to localized variations in snow-covered and frozen. Laser radar, visible-light
camera, millimeter-wave radiometer, and optical fiber sensors were installed,
and these four sensors have been operating continuously, collecting data since
December of last year. The collection of data is scheduled to continue until
September of this year. Fig. 3 shows the layout of sensors at Nakayama Pass.
The team also reviewed proposals for deployment of these sensors on actual roads.
As every area is already equipped with visible-light cameras, a system that
makes use of images from those cameras to determine road surface conditions
will be most capable of relatively early deployment in the field. The deployment
of road surface sensors is also being considered for bridges, overpasses, tunnel
entrances and exits, and other such locations where sudden changes can occur
in the road surface, as well as for mountain passes and other such sections
of road where weather conditions can change relatively rapidly.
| Fig. 2. Road Surface Sensor Field Operation Test Districts |
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| Fig. 3. Sensor Layout for Field Operation Test (Nakayama Pass) |
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3. Cruise Assist Information Systems (K3)
Cruise assist information systems comprise devices that use sensor, road shape,
weather, and other such data to create information to provide to drivers and
vehicles. In 2000, the team developed an algorithm for a headway maintenance
service utilizing road surface conditions and a cruise assist algorithm for
multiple safety services in support of driving safety. Proving tests were conducted
of the seven safety services individually. On actual roads, however, different
user services will be required at the same time. Pedestrian crosswalks, for
example, will need simultaneous support for prevention of crossing collisions,
support for prevention of right turn collisions, and support for prevention
of collisions with pedestrians crossing streets. The team created the algorithm
to provide this kind of service, and verified effectiveness of the algorithm
using simulation.
4. Vehicle Position Information Systems (K4)
The vehicle position information systems comprise devices that accurately determine
the position of vehicles in their traffic lanes and also provide information
that is specific to that position. The team has been conducting research on
lane markers (radio wave markers for information provision, and magnetic and
radio wave markers for lateral movement control). The proving tests employed
the radio wave markers for information provision and magnetic markers for lateral
movement control to verify the effectiveness of lane markers. Additional research
specifically in element technologies was carried out to verify the effectiveness
of lane markers in situations where snow-covered area has hidden the road surface
and made the lane markers invisible. In concrete terms, magnetic position markers,
and radio wave position and information provision markers were installed under
the road surface at the Ishikari Blizzard Test Station. Test drives made over
a 5-cm layer of compacted snow on the road confirmed that the markers yielded
the identical performance with snow-covered as without it. It was also confirmed
that sensor performance is not affected by deicing compounds. Fig. 4 shows an
overview of the tests conducted in cold climates with snow cover.
| Fig. 4. Overview of Testing in Cold Climates with Snow-Covered |
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5. Information Telecommunications Systems (K5) and Road-to-Vehicle Communications
The information telecommunications systems team performed evaluations of continuous
communications systems used in proving tests, and conducted research in spot
communications, which have shown potential for practical application in ITS
road-to-vehicle communications systems. The team had conducted research in continuous
communications systems using quadrature phase shift keying (QPSK) since 1996,
and was ultimately able to evaluate their effectiveness by proving tests. Fig.
5 is a layout diagram of the communications equipment installed in the proving
test system. Installed as part of the system for prevention of collisions with
forward obstacles on expressways, this is capable of stable continuous communications
within a 600-m or greater communications range that uses radio to chain together
six communications devices that each have a 100-m radio zone. Installed as part
of an intersection system, it provides communications capability along the approach
road 200 m before the intersection up to the point of departure from the intersection.
Proving tests were also carried out to verify the system's capability in road-to-vehicle
communications inside a tunnel. Fig. 6 shows an example of the radio-wave propagation
characteristics. A variety of tests have clearly shown that further study of
radio-wave skipping, the effects of architectural structures, and so on, will
be required. Studies were also made into the possibilities for scaling up road-to-vehicle
communications for use in ITS services other than Advanced Cruise-Assist Highway
Systems (AHS).
| Fig. 5. DSRC Layout for Proving Test System |
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| Fig. 6. Radio-wave Propagation Characteristics |
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A report to the Telecommunications Technology Council last year has made it possible for the amplitude shift keying (ASK) method of spot communications being used for electronic toll collection (ETC) to be used also for other services. The team studied the use of this communications format to AHS, and it appears that the way to practical application is open. The results obtained in communications systems and the issues foreseen for the future can be organized as follows:
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