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Outline of the Primary Requirements of Advanced Cruise-Assist Highway Systems |
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AHS is the central system of Smartway coordinating with Smart Cars and utilizing
real time information from Smart Gateways thus supporting the driver's operation,
improving traffic safety aim and efficiency, bettering the traffic environment,
and improving convenience and comfort for the driver which are among the main
purposes of the plans.
The primary requirements are presently in the phase of soliciting opinions
of relevant parties. It must be noted that the content of this report may be
modified following gathering and study into the opinions received.
The development project set priority to better safety, with research ed at
commercializing AHS that realize greater safety in the near future . The primary
requirements aim at identifying the requirements in AHS aimed at realizing this
goal |
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| 1.1 Outline of AHS |
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The support levels of AHS is divided into the three levels shown in Table 1.1, categorized by whether the driver or the system should gather information necessary for driving, operate the vehicle, and bear responsibility for driving. |
| table1.1 Support Levels of AHS |
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(1) AHS-i supports part of the information collection for driving.
(2) AHS-c supports part of the driving operation as well as the information collection.
(3) AHS-a fully supports the driving operation and the information collection,therefore,responsibility for safe driving belongs to the AHS-a system
. At present, R&D is focused on AHS-i and AHS-c considering the ease in mastery by users, breadth of service coverage, etc. Areas in AHS-a that are likely to become possible in the near future are automatic truck navigation in designated zones, automatic control of service vehicles such as snowplows, automatic navigation at low-speed platooning in congested areas, and automatic garage parking in parking areas. Since responsibility for cruising lies on the system side, basic studies are expected to be conducted on continuing basis in the area of laws and regulations, driver tolerance, cost effectiveness, etc.
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| 1.2 Creation of the Requirements |
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The requirements are necessary provisions on needed features and capabilities to described social needs in system development. Figure 1.1 shows the requirements on the system from social needs based on analysis of such needs. Requirements, in fact, bridge to gather social needs and system development. In development of AHS to achieve greater road safety, the requirements must be defined with an eye on social needs, that is, reduction of traffic accidents to the greatest possible extent within a reasonable range in driver acceptance, technical feasibility, and cost effectiveness. The system and the features and capabilities of the element technologies comprising the system must be defined to meet these requirements. The requirements described herein aim at specifying the basic common provisions in system development and do not include practical and commercial requirements needed in commercialization, thus do not unnecessarily hamper latitude in system development. The viability of the requirements must also be examined from the standpoint of technical feasibility and cost effectiveness. For this reason, the primary requirements are requirements still in the course of evolution and contain aspects to be modified by future research and proving tests. In this report, the assumptions on requirements for AHS integrating the vehicle and the road are defined first, followed by development of requirements (draft) based on the assumptions. |
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| Figure1.1Position of the Requirements |
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| (1) The Principles of the Requirements |
The definition of the requirements is based on the following principles. |
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| 1) Definition with Attention to User Acceptance and Social Acceptance |
Since the requirements emerge from needs toward the system, they must be defined so that they can be accepted widely by users and society. In the area of "improvement of safety," for instance, a requirement that is expected to achieve outstanding effect in reducing accidents through the system development but is not accepted by drivers or is not either cost-effective or practical technologically cannot be regarded socially appropriate. At the same time, it is important for requirements to evolve over time with growth in system use and greater mastery by system users. AHS must likely undergo continuing change in requirement with attention to development of trust between the driver and the system. |
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| 2) Definition Based on Statistical Figures and Data |
For rational definition of requirements based on needs, attention should be
paid on statistical data of traffic accidents, etc. and the analytic findings
of such data, as well as clarification of the basis of such data to the greatest
possible extent. Studies must also be made on their viability by gathering data
through proving tests, etc. |
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| 3) Service within the Limits of Road Possibility |
Although cruise support under inclement weather conditions is important, service under conditions in which car driving is generally regarded inconceivable reaches beyond the service range. For this reason, the requirements exclude service on highways or ordinary roads under torrential rains, large snowfall, thick fog, strong winds, when highways are closed, etc. |
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| 2.1 The Location and Scale of Traffic Accidents |
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| 2.1.1 Macro-analysis of Traffic Accident Statistical Data |
| Traffic accidents are a major social issue around the world. According to 1996 estimates by the International Road Traffic and Accident Database (IRTAD), some 500,000 died in traffic accidents worldwide - with 40,000 fatalities in the United States and 50,000 in Europe. In Japan, the number of traffic accident fatalities has remained roughly constant at around 10,000 every year for the past 20 years. However, the number of traffic accidents is on a steady rise. A comparative look into the fatality rate between Japan and other industrialized nations (number of traffic fatalities per 100 million vehicle/kilometers) shows that the rate in Japan is high. In order to achieve top-class motor vehicle traffic safety in Japan, more aggressive action is believed necessary to boost road safety. |
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| Figure2.1 Comparison of Accident Fatality Rates with Westerm Nations |
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| 2.1.2 Rise in Traffic Accidents with the Aging of Japanese Society |
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| (1) Accident Rate of Elderly Drivers |
| In the breakdown of frequency of accident fatalities caused by automobile driving,by number of driving license holders, by driving distance (vehicle/kilometers driven), and by age group, the frequency for elderly drivers (aged 65 or over) was found to be 1.28 times higher than for drivers aged 25 to 64. In accident fatality rate by vehicle/kilometers driven, the rate for drivers aged 25 to 64 was 1.15 persons per hundred million vehicle/kilometers. In contrast, the rate for elderly drivers was 2.83 persons per hundred million vehicle/kilometers, or 2.5 times more for younger drivers. Considering the high rate of traffic accident deaths and the rising age of the Japanese population in the years ahead, the problem is expected to become aggravated further. |
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| Figure2.2 Decline in Visual Acuity |
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| Figure2.3 Decline in Sensory Judgement |
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| (2) Causes of Accidents by Elderly Drivers |
| Generally speaking, elderly drivers suffer decline in visual acuity, including decline in vision in the dark, narrower field of vision, and decline in dynamic vision. In addition, simple responses time, including braking time, tend to become longer. The decline in such physical abilities is believed to be the cause of accidents by elderly drivers. |
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| 2.2 Selection of Principal User Services |
In the classification of traffic accidents on expressways and on ordinary roads, there are more collisions on expressways due to inadequate headway, collisions with obstacles and lane departure accidents. On ordinary roads, there are high rates of collisions with obstacles, lane departure accidents, crossing collisions, right turn collisions and collisions with pedestrians crossing streets. Services that prevent these accidents are necessary. Principal user services to be prioritized in R&D were selected in the declining order of services that account for the largest percentage in the number of traffic accident deaths and number of fatalities and injuries (that is, in the order of importance as social issue), so that 90% of the number is covered by the user services. Based on those results, it was decided to place high priority on R&D of the following seven user services.
* Prevention of collisions with obstacles
* Lane-keeping (curves)
* Lane-keeping (straight lane)
* Prevention of crossing collisions
* Prevention of right-turn collisions
* Prevention of collisions with pedestrians crossing streets
* Maintenance of safe headway |
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| 3.1 Policy on Tentative Requirements |
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| As described in Chapter 1, requirements for the first phase of AHS operation are founded on the following assumptions: 1) Accident prevention service for safety-conscious drivers 2) Service preventing excessive intervention in driver operation 3) Service within limits of road capability 3.2 Accident Countermeasure Model Figure 3.1 shows the process of accident occurrence and the model to prevent accidents. When a hazard presents itself, the basic behavior of the driver can be classified largely into "recognition" of the phenomenon likely to pose danger, "judgement" on the method to avert the danger, and "operation" for averting the danger. AHS is designed to avert accidents by taking action in some part of the process leading to an accident illustrated in the Figure. The requirements currently under study cover the quantitative requirements on the timing and method of providing information, warning and operational support in the user services shown in Figure 3.1, as well as conditions in weather, road environment, etc., when providing service. |
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| Figure3.1 Accident Occurrence Process and Prevention Model |
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| 3.3 Requirements |
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3.3.1 Common Items
(1) Cruise Support Method |
Cruise support by each principal user service is executed in three stages described below information,warning and operational support However, providing information for maintenance of safe headway lane-keeping,except in inclement weather, warning and operation support in prevention of right-turn collisions and prevention of collisions with pedestrians crossing streets were found to be excessive intervention with the driver and will not be provided. 1) Information to avert danger will be included to support hazard aversion executed with latitude in time and by the driver's free will.
2) If hazard approaches without the driver taking adequate counteraction, a warning will be set off to prompt the driver to take emergency action within the range that does not irritate the driver.
3) If the driver keeps ignoring the warning and accident cannot be averted, the system is to intervene and start emergency operation. |
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| (2) Speed Covered by Service |
| Assuming that the driver is conscious of safe driving, more or less 90% of traffic accidents are covered when occurring at a speed beneath the level recognized as hazardous based on traffic accident statistics. |
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| (3) Weather Conditions Covered by Service |
| Assuming that cruising support is given within the range of road capability, requirements for expressway closing shall be a meteorological limit for service coverage. ?EVisibility: More than 50 meters ?ERainfall per hour: Less than 50mm per hour ?E Wind velocity: Under 25 meters/second |
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| (4) Road Surface Conditions for Service |
| Service is to be provided as a rule on dry, wet, snow-covered, and frozen road surfaces. |
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| (5) Vehicles Covered by Service |
| Based on analysis of traffic accident statistical data, service shall be provided to vehicles including motorcycles, since most accidents are caused by vehicle models including motorcycles. However, service to motorcycles shall be limited to information and warning support. Operational support shall be provided to passenger vehicles or larger. |
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| (6) Service Time |
| Service shall be provided 24 hours a day. |
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| Figure3.2 Support Timing |
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| Table3.1 List Requirements(Summary) |
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| 3.4 Accident Reduction Potential |
| Figure 3.3 shows the possibility of the system being able to reduce accidents (accident reduction potential) if it is developed to meet the requirements mentioned. In the first phase of practical application, the range of system application is restricted by the requirements in cruising speed, etc. If the number of traffic accident fatalities excluded from the range of application is exempted, the numbers of fatalities and injuries possibly reduced by AHS in the first phase are estimated to be 5,742 and 600,000, respectively. This accounts for 60% of the number of total traffic accident fatalities. Even when the system is put into service, there is no guarantee that accidents caused by human error on the part of the driver, etc., can be effectively reduced. Regarding the efficacy of the system in accident reduction, evaluation is scheduled to be implemented by utilizing driving simulators, etc., in the future |
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| Figure3.3 Accident Reduction Potential |
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| Based on AHS requirements described in Chapter 3, the distribution of the systemsO required features between infrastructure and vehicle is being considered and the ability of the infrastructure is organized. |
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| 4.1 Policy on Vehicle-Road Distribution of System Features |
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| 4.1.1 Basic Policy |
Road and vehicle distribution of system features has been classified according to the basic policy below.
1) The road infrastructure, including sensors for detecting road conditions, is to gather information on road sections, chiefly curves and intersections, where visibility is poor, and "recognizes" road conditions. In addition, sensors on the vehicle gather information within the sensing range possible from the vehicle and "recognize" road conditions.
2) Information gathered by the vehicle is "transmitted" to the road infrastructure in road-to-vehicle communications (RVC).
3) Based on information gathered by the road infrastructure and information received from vehicles, it OjudgesO on danger potential of road conditions.
4) Information on dangerous phenomenon judged to exist by the road infrastructure is "transmitted" via RVC to the vehicle.
5) Based on information received, the vehicle "judges" timing of providing information,warning and operational support and executes cruising support ("operation") depending on vehicle position. When receiving cruising support either in providing information, warning or operational support, the driver is held responsible for driving. |
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| 4.1.2 Example of System Features Distribution between the Road and the Vehicle |
| As an example of distribution of system features between the road and the vehicle in line with the aforementioned policy, the features that should be provided on the road side in Prevention of Collisions with Obstacles and features to be provided by the vehicle are shown in Table 4.1 4.1.3 Summary of Infrastructural Features & Image of Equipment Application As shown in Table 4.1, distribution of features for each user service between road and vehicle is defined. This is followed by identification of system features to be provided by road infrastructure, and the relationship with features required by each user service is systematized. Furthermore, the road infrastructure equipment necessary for realizing the features of AHS and the required performance are organized in Table 4.2 |
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| 4.1.3 Summary of Infrastructural Features & Image of Equipment Application |
| As shown in Table 4.1, distribution of features for each user service between road and vehicle is defined. This is followed by identification of system features to be provided by road infrastructure, and the relationship with features required by each user service is systematized. Furthermore, the road infrastructure equipment necessary for realizing the features of AHS and the required performance are organized in Table 4.2. |
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| The Ministry of Construction and AHSRA plan to solicit participation from Japanese and foreign relevant organizations for proving tests of the seven user services in October 2000. The proving tests will be executed in cooperation with the ASV Project under the Ministry of Transport. The proving tests are aimed at evaluation of system efficacy in accident prevention and user acceptance and on assumptions in developing the requirements |
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Table4.1 Distribution of Road and Vehicle Features in Prevention of Collisions with Obstacles
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Features |
Feature Class |
Distribution between Road and Vehicle |
| 1 |
Gauging presence/absence of obstacle ahead of the serviced vehicle |
Recognition |
Share of the duty on the road if visibility from vehicle is poor 130 meters ahead due to curve, etc.Other are on the vehicle. |
| 2 |
Gauging presence/absence of pedestrians walking along the road in the same direction or in the opposite directions |
Share of the duty on the road when pedestrians crossing street cannot be identified easily. |
| 3 |
Gauging cruising environment (road surface conditions) ahead |
Share of the duty on the road; necessary in areas with rapid change in condition (area that affects vehicle behavior) |
| 4 |
Presentation of road shape data for assessment of road shape ahead of the serviced vehicle |
Road ?g |
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Detection of own vehicle position for correct assessment of obstacle position by the serviced vehicle |
Share of the duty on the road for key position, vehicle for distance measurement |
| 6 |
Detection of serviced vehicle position, speed, acceleration, yaw rate, etc. |
Vehicle |
| 7 |
Information processing to provide information gathered by road infrastructure to the vehicle |
Judgement |
Road |
| 8 |
Presentation of data processed by the road infrastructure to the vehicle |
Transmission |
Road [provided within range of 130 meters (for ordinary road) or of 300 meters (for expressways) from obstacle] |
| 9 |
Reception of the data above and integration with information gathered by the vehicle. |
Vehicle |
| 10 |
Judgement of collision potential based on position, speed, etc., of serviced vehicle and position, size, etc., of the obstacle |
Judgement |
Vehicle |
| 11 |
Providing information to the driver on whether an obstacle lies ahead |
Operation |
Vehicle |
| 12 |
Warning on danger of collision if the driver fails to take evasive action after providing information |
Vehicle |
| 13 |
Support in obstacle evasion, such as deceleration, if the driver fails to take evasive action after alarm is set off |
Vehicle |
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| 5.1 For Development of the Secondary Requirements |
| Research on the requirements is expected to continue on (1) evaluation of efficacy of the principal user services in reducing traffic accidents; (2) study into the technical feasibility of system component devices; (3) effect of system application and estimation of system installation costs, etc. The findings of these studies will be organized in the secondary requirements. |
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| The primary requirements (draft) introduced in this paper are still in the midst of compilation. Development of requirements by AHSRA which satisfy users is anticipated. Finally, we would like to express our heartfelt appreciation to Manager Hosaka, Manager Kamata, Manager Mizutani, Manager Kowa, Leader Komada, and Leader Ishizaka of the AHSRA Requirements Task Force for their valuable cooperation in compiling the draft for the primary requirements. |
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Table4.2 Performance Required of Infrastructural Equipment(Summary)
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Infrastructural Facility |
Required Performance |
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Information- gathering sensor facilities |
Vehicle detection facility (vehicle with four wheels) |
Detection range: 0-160m for ordinary roads; 0-300 or more for expressways
Identification performance: Position & speed of object of size larger than a subcompact vehicle
Positioning accuracy: No more than 5% in margin of error in longitudinal direction; less than 1/4 the lane width in lateral direction
Speed measurement range: More than 0-120 km/h vehicle cruising speed on expressways (0-180 km/h recommended on expressways) More than 0-70 km/h vehicle cruising speed on ordinary roads (0-120 km/h recommended on ordinary roads) Speed measuring accuracy: No more than 5% margin of error Detection time: Less than 0.1 second; detection cycle 0.1 second |
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Vehicle detection facility (motorcycles) |
Detection range: 0-274m for ordinary roads
Identification performance: Position & speed of object of size larger than a motorcycle
Resolution: Identification separately of motorcycle cruising normally and motorcycle cruising alongside four-wheel vehicle Positioning accuracy: No more than 5% in margin of error in longitudinal direction; less than 1/4 the lane width in lateral direction
Speed measurement range: More than 0-80 km/h vehicle cruising speed on expressways (more than 0-120 km/h recommended on ordinary roads)
Speed measuring accuracy: No more than 5% margin of error Detection time: Less than 0.1 second; detection cycle 0.1 second |
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Pedestrian detection facility |
Detection range: Pedestrian crossing & periphery (width) pedestrian crossing and 4m margin; (length) 15m Pedestrian walking along road in same or opposite direction of vehicle (width) roadside path with 0.5m margin; (length) 200m However, measurement in 200m segments possible
Identification performance: Presence of pedestrians or people on bicycles Less than 1/4 of land width at position of pedestrian, etc., within detection range
Detection time: Less than 0.1 second; detection cycle 0.1 second However, detection performance and cycle of less than 0.5 second possible because human speed is at 1 m/s |
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Road surface condition detection facility |
Detection conditions: Dry, wet, frozen, and snow-covered surfaces
Detection range: Area that affects vehicle behavior within monitoring range in full width of road width and direction of lane Detection accuracy: The four aforementioned surface conditions Range of output unit: Detection range segmented to minimum area of unit affecting service (unit segment) and output of condition representing the segment (detection range same as unit segment). However, it a service segment extends for several kilometers as between
interchanges, as in maintenance of safe headway service, road condition in the service segment can be estimated by measuring a number of points where road condition changes.
Detection time: Less than 1 minute (since road condition change is approx. 1 minute)
Information update cycle: Within 10 seconds |
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Positioning support facility |
Detection position: Lateral & longitudinal position within lane Transit speed: Detection possible at more than 120 km/h vehicle cruising speed
Detection range: All service segments
Detection accuracy: Lateral position accuracy of less than 5cm in error margin Longitudinal position accuracy of less than 1m (at high speed) or less than 0.25m (at low speed) in error margin Environmental conditions: Stable operation in road flooding, snow cover, or freezing Stable operation in pressed snow thickness of more than 5cm
Installation requirement: Embedding in road surface recommended Standard point data volume: More than 9 bits |
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Road-to-vehicle communication facility |
Communication target: AHS vehicle (installable on motorcycle or larger vehicles)
Communication target speed: Between 0-120 km/h Between 0-180 km/h recommended
Communication range: 0-600m on expressway; 0-420m on ordinary road 3 or more lanes in one direction of expressway; more than 6 lanes on ordinary roads
Number of target vehicles: Individual communication to more than 252 vehicles 252 on 600m of 3 lanes on expressway with vehicle density of 140 per kilometer164 on two lanes in each direction on ordinary road with vehicle density of 140 per kilometer Information update cycle (communication cycle): 0.1 second |
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Roadside processing device |
Targets: AHS-i and AHS-c vehicles
Description: Information processing &management/administration Cruise-assist algorithm for realizing each user service Road shape database management Management of all of the devices (equipment failure control, management history management, program download, database management, etc.)
Processing speed: Data processing to complete within 0.1 second (excluding management feature) |
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Common specifications |
Weather conditions: Operation at visibility of more than 50m Rainfall of less than 50mm/hour Wind velocity of less than 25 m/s
Detection of problem: Equipped with self-diagnosis capability of design (excluding position detection assistance facility) and stop when necessary
Problem notice: Notification to vehicle of equipment problem detection, operation stop, etc. |
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