1. Road Condition Assessment Sensors

(1) Purpose of Research

   The purpose of this research has been to develop road condition assessment sensors that measure the position and speed of a vehicle with great accuracy, and that reliably detect stationary vehicles, people, bicycles, and other such obstacles in real time.

   A further purpose has been to develop sensors that are capable of applying AHS technology effectively for utilization in road management.

(2) Research Flow

   The flow of this research, which began in 1996, is shown in the figure. (Figure 1)

(3) Fiscal 2001 Research Plan

• Element Technology Field Tests on Actual Roads
     First, this involved improvement of algorithms for optical, infrared, and millimeter wave sensors in a heavy traffic environment, then verification and evaluation of the improvement impact on performance and of safety and reliability.
     Second, plans were made for evaluation of reliability in a severe natural environment. Specifically, this involved formulation of a testing plan for implementing verification and evaluation of performance, safety, and reliability.
  
  
• Study of Methods for Detecting Vehicles Squeezing Through and Preliminary Feasibility Survey
     This is a key technology for intersection services. Specifically, this work involved a study of detection methods using two types of sensor, millimeter wave and laser, a survey of their feasibility, and verification of their basic performance.
  
  
• Study of Effective Utilization of Road Condition Assessment Sensor Systems for Road Management, Etc.
     This was a study of the utilization of cameras used in road management.
  

(4) Test Configuration in a Heavy Traffic Environment (Tomei Expressway, Ashigara Service Area Vicinity)

   This is on the highway outward bound from Tokyo, and it has average daily traffic of 40,000 vehicles. There are millimeter wave, optical, and two infrared sensors in an integrated configuration, with a traffic counter installed for reference. The resulting data and weather-related information are made available by means of ISDN, and the system also allows remote observation over the Web. (Figure 2)

(5) Plan for Evaluation in a Severe Natural Environment (Oita Highway, Hiji Junction)

   The plan is to evaluate detection rate, position accuracy, and speed accuracy under fog and rain visibility conditions at the Hiji Junction on Oita Highway for field tests on actual roads in fiscal 2002. This location has an annual average of 90 days of fog with visibility of 50 m or less. (Figure 3)

(6) Study of Methods for Detecting Vehicles Squeezing Through and Preliminary Feasibility Survey

   Tests are being conducted at the test course of the National Institute for Land and Infrastructure Management (NILIM). Laser sensors are used to plot the track of motorcycles and bicycles squeezing through between lanes or on the shoulder past heavy duty vehicles and passenger vehicles that are at rest on the road. (Figure 4)

(7) Results from Fiscal 2001

   The tests at the Ashigara Service Area (road section of uninterrupted flow field in a heavy traffic environment) were used to improve the algorithms and optimize the parameters for infrared and millimeter wave sensors. This resulted in achievement of the provisional target values for safety and reliability (96% in terms of detection rates (based on detecting not only each vehicle but vehicle groups) ).

   Preliminary tests that assumed a stop vehicle group in a congestion conducted for detection of vehicles squeezing through confirmed the superior performance of laser sensors with vehicles at detectable intervals. The basic characteristics have also been confirmed as offering the possibility for detection of motorcycles squeezing through in the sensor's field of vision within 50 m from the center of the intersection.

   With respect to effective utilization for road management, algorithms are being developed for cameras with turn and zoom functions that are used for road management.

(8) Fiscal 2002 Research Plan

   Element technology field tests on actual roads will continue verification in a heavy traffic environment in a location subject to heavy rain and fog.

   With regard to detection of vehicles squeezing through, there are plans to implement evaluations of the detection characteristics of vehicles squeezing through at normal speeds, and evaluations of intersection sensor systems to address the issue of shadowing.

   With respect to effective utilization of AHS sensors for road management, functions geared to cameras with turn and zoom capability are scheduled to be verified, and their effective utilization for road management is to be studied.

2. Road Surface Assessment Sensors

(1) Purpose of Research

   The purpose was to develop road surface assessment sensors capable of reliable, real-time detection of road surface conditions that have a significant influence on vehicle behavior (particularly braking and steering). An additional purpose was to develop sensors using AHS technology that are capable of effective utilization for road management.

(2) Research Flow

   Research started in fiscal 1996 with surveys of technology and development of algorithms. From fiscal 1998, tests were made of artificial road surfaces, and from fiscal 2000, element technology tests on actual roads. (Figure 5)

(3) Fiscal 2001 Research Plan

• Element Technology Field Tests on Actual Roads
     Performance, safety, and reliability evaluations are being conducted at the Nakayama Pass in Hokkaido, the Ibuki Service Area on the Meishin Expressway, and on actual road at the Hokuriku Regional Construction Bureau. The four types of sensors being used are laser radar, radio radiation meter, visible image, and optical fiber sensors. The specific areas being addressed are improvement of sensor algorithms to improve performance, verification of improved detection performance, and clarification of performance limits.
  
  
• Improvement of detection performance by utilization of other information, study of safety and reliability improvement
     Specifically, this involves the use of other meteorological instrument data, and forming combinations with other sensors.
  
  
• Study of layout, inspection methods, and maintenance operation of road surface assessment sensors
  

(4) Test Configuration in an Actual Road Field Environment (Nakayama Pass)

   Laser radar, optical, and radio radiation meter sensors were installed, as well as optical fiber sensors buried in the road shoulder for a length of about 500 m. Three reference cameras were installed to keep track of the road surface. The performance is being verified using these data together with data from meteorological instruments, made available by means of ISDN for remote observation over the Web. (Figure 6)

(5) Summary for Fiscal 2001

• Improvement of detection performance was verified and performance limits were clarified by element technology field tests on actual roads. Specifically, this involved verification of sensor detection characteristics by means of data for the year. Issues and points for improvement were also identified for each sensor.
  
  
• Detection performance, safety, and reliability were improved by the use of other information. The use of meteorological instrument data included utilization of rain sensor data for early detection of the beginning of rainfall in order to improve moisture detection performance. It was also confirmed that the reliability of optical sensors could be improved by using them in combination with other sensors at times when optical sensors are not capable of detection (such as in backlight from the setting sun, etc.).

(6) Issues for the Future

• For the study to be conducted of provisional target values for safety and reliability, the data from field environments on actual roads should be analyzed. Verification and evaluation of detection performance and so on should be implemented.
  
  
• Study should be conducted of measures to improve detection performance and so on by the utilization of other information.
  
  
• Proposed detection systems should be verified, and study should be conducted of their multifunction application to enable effective use of these systems for road management

3. Position Detection Technology

   The purpose of lane marker research is to develop highly reliable, highly accurate position detection technology for AHS services. The purpose of research on technical trends is to examine position detection technologies capable of application in AHS and other services of every kind, bearing in mind advances in position detection technology and in social needs.

   The flow of research is illustrated in the figure. (Figure 7)

(1) Lane Markers

I. Overview of Research

   Lane markers are of two types, magnetic and radio. All evaluations of both types were completed by implementation of the fiscal 2001 topics for evaluation. (Figure 8)

II. Summary of Results

   The results for fiscal 2001 included installability and in-vehicle mountability for radio marker systems. It was found that some modification of the marker construction made it possible to avoid being influenced by steel reinforcements, steel plate, and other such road structures. It was also confirmed that mounting the equipment in passenger vehicles and trucks posed no problems.

   In connection with the provision of start point information by the arrangement of magnetic markers and radio markers, a radio marker with a two-bit reflection phase was developed. This made it possible to provide lateral position and start point information, and enabled magnetic tape sequential layout. It was confirmed that start point detection is possible with a strip-like magnetic marker arrangement. (Figure 9) Study is also underway to confirm the usefulness of the magnetic tape sequential layout for longitudinal position detection.

   A comprehensive technical comparison of magnetic markers and radio markers has been completed and the findings have been organized in terms of performance, installability, in-vehicle mountability, and so on. Both are highly accurate, highly reliable position detection systems, and their technical feasibility is being verified accordingly.

(2) Survey of Technical Trends

I. Overview of Research

   This was approached from two directions. One approach was situated as a survey and systematic ordering of position detection technology, for which the newest levels of position detection technologies were surveyed and their performance in terms of functionality, position accuracy, and so on, together with conditions of application and so on were placed in systematic order. The other approach systematically ordered the applications and the conditions required with respect to position detection technology. This addressed the AHS/ITS applications, specifically the 172 sub-services involved, which were ordered by position measurement accuracy and conditions required in terms of position detection technology.

   The next step was to use position accuracy as a parameter to select those position detection technologies that would be effective in handling the applications. Out of this group, technologies were further selected by such factors as position detection accuracy and shared use of position detection. In this way, the position detection technologies were systematically ordered in terms of their feasibility as AHS position detection systems. Substantiation and evaluation was performed on three items considered to require such assessment.

   Four position detection technologies were identified as highly feasible, namely, lane markers (magnetic tape sequential layout), GPS (including pseudo-satellite), direction of arrival (DOA), and a simplified form of dedicated short range communication (DSRC). (Figure 10)

II. Summary of Results

   It has been inferred from the survey of position detection technologies that a system combining improved-accuracy GPS with improved-reliability lane marker detection was a technology offering the possibility of accuracy and reliability on a par with the lane marker system.

   Based on the survey of position detection technologies, GPS (high-level), simplified DSRC, DOA, and lane markers (magnetic tape sequential layout) were identified as useful position detection technologies not only for AHS but also for a variety of other application services.

   The basic evaluation of the strongest position detection technologies resulted in selection of pseudo-satellite GPS, DOA, and simplified DSRC. Their basic characteristics and accuracy are being confirmed by basic evaluation conducted on the test course. The results show that pseudo-satellite and DOA have an accuracy within 1 m, and simplified DSRC within 10 m.

III. Issues for the Future

   The deployment of services in terms of applications must also be considered when selecting position detection technologies. This selection, therefore, was made on the assumption of deployment scenarios for AHS, ITS, and other such services. The basic technical tests were tests of position accuracy conducted using systems combined with DOA and DSRC, including combinations in which position detection and the detected information are provided to the vehicle from DSRC. The items included in tests of pseudo-satellites included their coverage range and position accuracy.

4. Road-to-Vehicle Communication (DSRC)

(1) Purpose of Research

   The purpose is to develop a road-to-vehicle communication system that transmits various types of information from the infrastructure to the vehicle without fault and in real time for use in operational support to the driver.

   The research plans up to the present are as shown. (Figure 12)

(2) Fiscal 2001 Research Plan

   The preconditions for road-to-vehicle communications in cruise assist services as regards multi-purpose applicability are that the road-to-vehicle communications for early practical application will make use of spot communication to provide multi-purpose applicability to AHS, road management, and other such applications utilizing the Association of Radio Industries and Businesses (ARIB) STD-T75 radio standard, and that the road-to-vehicle communications for early practical application will provide position detection support functions for start points and so on. As regards timeliness in operation, the system is expected to update information on a 0.1-second cycle.

   The research plan calls for (1) study and evaluation testing of the road-to-vehicle communications system requirements and adoption specifications. Specifically, this includes (2) study of the target values for safety and reliability in the system for early practical application, and (3) study of continuous communications (new DSRC technology) for more advanced AHS services.

   The method for performance evaluation of spot communication DSRC is divided into three parts. Radio testing will be carried out on the NILIM test course and on actual roads and trial calculations and simulation. (Figure 13)

(3) Results from Fiscal 2001

   The test evaluation of the spot communication DSRC confirmed the basic characteristics of this system and identified certain issues.

(a) Radio Zone Test Evaluation: The system was confirmed to provide a radio communication zone. However, radio wave skipping poses a problem.

(b) Radio Wave Interference: The installation spacing was calculated provisionally from the frequency allocations, radio zones, and so on, then confirmed by actual measurement.

(c) Communication Quality: The bit error rate in the radio zone was measured and confirmed to be less than 10-5.

(d) Start Point Position Accuracy: Tests conducted in different lanes and at different cruising speeds confirmed a position accuracy within ±5 m. There were places, however, where the variation in position accuracy grew larger with the speed.

(e) Radio Wave Leakage: Tests conducted on the Oji Line of the Tokyo Metropolitan Expressway confirmed that radio wave leakage occurred at levels such that the signals could be received on adjacent roadways.

   The study of provisional target values for safety and reliability in the system for early practical application also led to adoption of provisional target values.

   In connection with continuous communications, work categories were isolated and systematized in view of standardization of the ARIB continuous communications system. A desktop study was also made of the technical issues posed by continuous communications DSRC (multipath measures, shadowing measures, and handover measures).

(4) Issues for the Future and the Fiscal 2002 Research Plan

   Planning is underway to address the issues of radio wave skipping and leakage by reviewing the respective requirements and so on under the categories of design of non-response ranges and design of installation conditions for aerial wires.

   Testing of the interconnectivity of roadside units, in-vehicle devices, and so on involves study in sequence of the respective preconditions, test categories, and so on for the equipment. Interconnectivity tests will be carried out, and draft standards will be created.

   The safety and reliability of services for intersection systems will be addressed by study of measures to reduce the occurrence of failures to danger and by establishment of tentative target values.