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Appraisal of Feasibility of Using Vehicle-to-Vehicle Communications for Safe Passage of Unsignalled Road Intersection under Varying Conditions
12th IFAC Conference on Programmable Devices and Embedded Systems The International Federation of Automatic Control September 25-27, 2013. Velke Karlovice, Czech Republic
Appraisal of Feasibility of Using Vehicle-to-Vehicle Communications for Safe Passage of Unsignalled Road Intersection under Varying Conditions J. Ahrems Department of Transport Electronics and Telematics, Riga Technical University, Lomonosov Str. 1,V korpuss, LV-1019, Riga, Latvia (e-mail: [email protected]) Abstract: Improvement of road traffic safety is one of the principal directions in development of intelligent transport systems. Exchange of information about transport vehicle location and movement parameters by means of vehicle-to-vehicle (V2V) communication is designed to significantly improve the operation of the existing systems for warning drivers of hazardous situations on roads. The present article examines the feasibility of using V2V communications under varying conditions to ensure safe passage of an unsignalled road intersection. Keywords: Road accidents, Vehicle safety, Intelligent transportation systems, Intelligent vehicles. The algorithm offered in [1] operates unassisted by road infrastructure and may be used on any unsignalled road intersection. This algorithm enables to assess the safety of road intersection passing by forecasting the minimum distance between the moving transport vehicles.
1. INTRODUCTION The rapid motor transport development, in terms of both quality and quantity, has generated quite a few problems in the sphere of road traffic safety. Modernization of the existing road infrastructure and creation of new state-of-theart systems, especially in communication, are aimed at reducing the number of road traffic accidents.
The information about location, speed and heading in this case is obtained by GPS. The data exchange is carried out with the help of DSRC (Dedicated Short Range Communication). Due to information exchange, the motion parameters of both cars are known to each of them. The given algorithm fires every second upon arrival of a signal from the one’s car GPS receiver and data on the other car’s motion parameters as obtained via DSRC. The result of the calculations is the predicted minimal distance between the cars. Using these data the system produces a warning message for the car driver.
For vehicle-to-X communication it is necessary, that all participating parties agree on a common standard. The currently foreseen standard for this specific type of communication is IEEE 802.11p. Basically it is one amendment within the family of IEEE 802.11 standards that define the widely used technology for wireless local area networks (WLAN). IEEE 802.11p is adapted to the specifics that have to be respected in V2V (vehicle-to-vehicle) and V2I (vehicle-to-infrastructure) communications. In this case, the IEEE 802.11p standard defines the lower levels of the model OSI, including physical, and IEEE P1609 standart - the highest levels. The messages protocol for V2V communication sets the standard SAE J2735.
The prerequisite for the given algorithm’s operability is periodicity and reliability of information obtained through vehicle-to-vehicle communication. However, an urban environment provides many challenges for vehicle-to-vehicle communication. These include multiple propagation paths and many occlusions, particularly in areas where V2V messages would be most useful such as buildings, and others obstructions.
According to statistics driver error is the most frequent cause of accidents. One of the most dangerous places on the roads are the intersections without traffic light regulation. To prevent road traffic accidents on such intersections, we suggest the use of driver-warning systems based on exchange of information obtained through the GPS and the V2V and V2I data exchange systems.
This paper considers the possibilities of using the given algorithm under varying conditions both within and outside the boundaries of a populated area. 2. ALGORITHM APPLICATION FEASIBILITY CRITERION
The algorithm, which is presented in [6], provides for the use of road infrastructure. The given algorithm requires the use of a set of road traffic sensors, infrared transmitters and information and the V2I communication system. Besides, each motor vehicle must be equipped with an infrared signal receiver and a DSRC transceiver. Obviously, this algorithm may function on specially equipped intersections only.
978-3-902823-53-3/2013 © IFAC
One of the prerequisites of passing an intersection safely is the presence of only one vehicle at the intersection. So, on receipt of a possible collision warning signal, the driver must be able to bring his car to a halt before crossing the traffic lanes.
84
10.3182/20130925-3-CZ-3023.00019
IFAC PDeS 2013 Velke Karlovice, Czech Republic
Assuming proper operation of the brakes on the vehicle, the minimum stopping distance for a vehicle is determined by the effective coefficient of friction between the tires and the road, the driver's reaction time in a braking situation and the brake system’s reaction time.
The Graphs in Fig. 2 show the distance covered by a vehicle to a full halt versus the initial speed of the vehicle for various values of coefficient of friction between the tire tread and the road surface. For this purpose, the average time of driver’s reaction to the brake actuation is assumed to be 1.2 sec [2], and the braking system’s reaction time – 0.2 sec.
The friction force of the road must reduce vehicle’s speed to zero as shown in Fig. 1.
Fig. 1. Vehicle stopping distance. In order to stop a car, the kinetic energy must be reduced to zero or the kinetic energy must equal the energy given by the friction force [4] as shown in (1):
Ff d
mv 2
2 0
mgd ,
Fig. 2. Stopping distance/initial speed relationship for different µ values. It is obvious, that within the boundaries of a populated area, given the maximum allowed speed of 50 km/h, the minimum distance covered by a vehicle to a standstill under the worst conditions will be 44 m. Outside the boundaries of populated areas, given the maximum allowed speed of 90 km/h, the aforesaid parameter will increase to 114 m.
(1)
F f - friction force; m - vehicle’s mass; v0 vehicle’s initial speed; d - stopping distance; 2 g 9.8m / s ; - coefficient of friction between the tires where
Therefore, the prerequisite of using the proposed algorithm is the opportunity of receipt of a warning signal at least at 44 m to the intersection within the a populated area, and at least 114 m – outside its boundaries.
and the road. For calculating minimum stopping distance, a value of 0.8 is a nominal value for the coefficient of static friction between good tires and a good road surface. Almost always, coefficients of kinetic friction are less, and are dramatically less for wet, icy, slick, sandy, dirty very smooth or oily surfaces. It can be 0.7 or 0.6 for a vehicle with normally driven and worn tires. Poor condition tires might yield 0.5 or 0.4 for a closer representation of friction.
3. VEHICLE EQUIPMENT CONFIGURATION Two motor cars were used for test purposes; each of them was equipped with a system, whose structural scheme is given in Fig. 3.
Therefore, the distance covered by a transport vehicle to standstill may be expressed as (2):
d
(t dr
t br )v0
v02 , 2 g
(2)
where t dr - driver's reaction time; t br - braking system’s reaction time.
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IFAC PDeS 2013 Velke Karlovice, Czech Republic
The ML5805 is a single chip fully integrated Frequency Shift Keyed (FSK) transceiver developed for a variety of applications operating in the 5.725GHz to 5.850GHz unlicensed ISM band. The transmit power of the transmitter is +21 dBm, and the receiver sensitivity is as good as that, namely, -97 dBm [5]. In ideal conditions, given there are no obstacles that could cause reflection, diffraction and dissipation, within line-ofsight between the transmitter and the receiver, the radio signal transmission losses for a definite frequency in free space may be expressed as follows (3):
PL
32.44 20 lg F0
20 lg D0 ,
(3)
Where PL - radio signal transmission losses (dBm), F0 carrier frequency of transmitted signal (MHz), D0 - distance between the transmitter and the receiver (km). Fig. 3. Structural flowchart of vehicle onboard equipment.
Thus, for the given parameters - PL not higher than 118
A GPS receiver GARMIN GPS-25LVC with an output in the NMEA 0183 format [3] provides the system with information about the current location, heading and speed of the car.
dBm, F0 = 5787,5 MHz, the maximum possible expected distance between the transmitter and the receiver must not exceed 3.6 km. Practically, the ideal situation upon which this equatation was derived is not realistic.
A 5.8 GHz DSRC transceiver shown in Fig. 4, based on a ML5805 microchip, enables the exchange of the obtained information with another transport vehicle.
The device has an omnidirectional, rooftop-mounted antenna as shown in Fig. 5. To exclude cable losses, the antenna must be connected directly to the high-frequency part of the transceiver.
Fig. 4. Onboard 5.8 GHz equipment. Fig. 5. Car with onboard equipment.
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IFAC PDeS 2013 Velke Karlovice, Czech Republic
Controller µC1 provides for data collection from the GPS receiver, data receipt and transmission to the transceiver and data transmission to the PC or CPU for processing. The transmitter units on both cars operate in a broadcast mode with the transmission periodicity of 1 sec. Such a periodicity depends on the updating frequency of data received from the GPS receiver output. The RMC (Recommended Minimum Specific GPS/TRANSIT Data ) command received from the GPS receiver contains a time marker, the vehicle’s latitude and longitude data, its speed and heading angle in relation to grid North. For over-the-air transmission, the given command is supplemented with a conditioning preamble, a synchronizing sequence and a checksum. Under broadcast data transfer operation, i.e. without acknowledging the receipt, the check sum enables evaluation of the reliability of the received data set, and the time marker enables to state the fact of any losses of transmitted data sets. For data set transmission, a high bit rate hardware port of a μC1 microcontroller is used. The info rate is 1.536 Mb/s. As a result, the transmission via a low bit rate port of a microcontroller to PC contains a time marker and information about the position, speed and heading angle of the two tested vehicles. Coordinates conversion and mathematical implementation of the algorithm of possible collision warning at an intersection are performed by a personal computer (PC).
Fig. 6. Road intersection with low-rise urban structures. Test drives 4 and 5 were conducted in the area of multi-storey buildings with extreme development density as shown in Fig.7.
4. TESTS RESULTS
During the test drive, one of the tested vehicles was in static position at various distances to a road intersection, while the second car was moving towards the intersection by crossing course.
The performed tests resulted in determination of the maximum possible ranges of reliable-service distances for various terrains, which confirms the feasibility of the use of the given algorithm for safe passage of a road intersection. Test drives were held in an urban territory with various types of buildings. Test drive Nr. 1 was conducted within line-ofsight between the transmitter and the receiver without any obstacles on the radio signal path. The results of Test drives 2 and 3 demonstrate the possibility of V2V communication in the area with two-three-storey buildings around the road intersection and with a low development density of the area as shown in Fig.6.
87
IFAC PDeS 2013 Velke Karlovice, Czech Republic
Fig. 8. Scheme of road intersection with distances. In conditions of direct visibility (test Nr.1) – absence of any constructions – the maximum distance between cars enabling information exchange is 495 m, which is equivalent to the distance of about 350 m to the intersection. In the given case, therefore, the use of the vehicle-to-vehicle communications system for safe crossroad passing will be possible even at the speed of 90 km/h, i.e. outside populated areas.
Fig. 7. Road intersection with multi-storied urban structures. The data obtained as a result of the performed tests are shown in Table 1: Table 1. Tests results Test Nr. 1 2 3 4 5
d1, m 350 80 80 60 15
d2, m 350 140 180 26 83
D, m 495 161 197 65 85
In conditions of low-rise urban structures (up to 3 storeys high), the maximum possible operable distance of the system is significantly lower, as shown in Table 1, tests Nr. 2 and Nr.3. That can be explained by the different conditions of radio-wave propagation, re-reflection and the low altitude of location of the transceiver antenna.
q, % 93 85 87 63 75
Nevertheless, the maximum distance from an intersection enabling information exchange is in the range of 80-180 m, which significantly exceeds the established criterion for an urban environment, i.e. 44 m.
Where d1 is the distance between the first (static) motor vehicle and the intersection, d2 – maximum distance between the second vehicle and the intersection, at the moment of receipt of the first data set, D – real maximum radio range as shown in Fig. 8.
In such a case, the number of correctly received data packets falls within the range of 87-93%, which, in view of the slow response of the motor vehicle, does not affect the system operability.
The q parameter estimates the ratio of the correctly received data sets number to the total number of data sets transmitted during the communications period. The number of data sets transmitted during the communications period is determined using time markers and the known transmission periodicity of 1s. The validity of the received data set is confirmed by a checksum.
The worst conditions for application of the given kind of vehicle-to-vehicle communications are observed in urban areas with multi-storied structures as shown in Table 1, tests Nr. 4 and Nr. 5.
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IFAC PDeS 2013 Velke Karlovice, Czech Republic
In such cases, sustained exchange of information is only possible at 15-25 m to the intersection, which is insufficient according to the chosen speed criterion of 50 km/h. It is obviously impossible to apply the algorithm for safety passing of an intersection under the said conditions on the basis of vehicle-to-vehicle communications alone. The accomplished tests have shown that the presence of buildings and other obstacles significantly reduces the V2V communication rate in comparison with the estimated rate for free space. When comparing the test drive results with the aforesaid criteria, it becomes evident that the use of the proposed algorithm for safe passage of an unsignalled intersection is feasible under the conditions of line-of-sight and low-storey development. In conditions of multi-storey urban development, it is impossible to use vehicle-to-vehicle communication alone for intersection passage safety purposes. In the given case, it is worthwhile applying algorithms based on an integrated use of the V2V and V2I communication systems. 6. CONCLUSIONS The present paper provides the feasibility criteria for the application of the algorithm for safe passage of an unsignaled intersection using the vehicle-to-vehicle communication system only. On the basis of the results of the performed tests, we have assessed the system feasibility and made conclusions on the system applicability under varying conditions both within and outside the boundaries of a populated area. Further possibility research of applying of the algorithm provide for tests for moving cars, as well as increasing the vehicles involved in the tests. REFERENCES Ahrems J., Algorithm for determination of safety intersections. In Proc. 13th Biennial Baltic Electronics Conference (BEC2012), Tallinn, Estonia, 2012, pp.175178. Mehmood A., Easa S. M., Modeling Reaction Time in CarFollowing Behaviour Based on Human Factor. International Journal of Engineering and Applied Sciences. 5:2 2009, pp. 93-101. NMEA 0183 Standard for Interfacing Marine Electronics Devices, Revision 3.01, NMEA Standard 0183, 2000. RF Microdevice Data Manual, RFMD Inc., 2008. Popescu-Zeletin R., Radusch I., Rigani M. A., Vehicular-2-X Communication. Springer-Verlag, Berlin, 2010. RFMD Inc., RF Microdevice Data Manual, RFMD Inc., 2008. Tsukada N., Yamada K., Takahashi S., Development of Driving Safety Support Systems for Non-right-of-way Vehicles at Unsignalized Intersection. 19th ITS World Congress, Vienna, Austria, 22/26 October 2012.
89
Appraisal of Feasibility of Using Vehicle-to-Vehicle Communications for Safe Passage of Unsignalled Road Intersection under Varying Conditions J. Ahrems Department of Transport Electronics and Telematics, Riga Technical University, Lomonosov Str. 1,V korpuss, LV-1019, Riga, Latvia (e-mail: [email protected]) Abstract: Improvement of road traffic safety is one of the principal directions in development of intelligent transport systems. Exchange of information about transport vehicle location and movement parameters by means of vehicle-to-vehicle (V2V) communication is designed to significantly improve the operation of the existing systems for warning drivers of hazardous situations on roads. The present article examines the feasibility of using V2V communications under varying conditions to ensure safe passage of an unsignalled road intersection. Keywords: Road accidents, Vehicle safety, Intelligent transportation systems, Intelligent vehicles. The algorithm offered in [1] operates unassisted by road infrastructure and may be used on any unsignalled road intersection. This algorithm enables to assess the safety of road intersection passing by forecasting the minimum distance between the moving transport vehicles.
1. INTRODUCTION The rapid motor transport development, in terms of both quality and quantity, has generated quite a few problems in the sphere of road traffic safety. Modernization of the existing road infrastructure and creation of new state-of-theart systems, especially in communication, are aimed at reducing the number of road traffic accidents.
The information about location, speed and heading in this case is obtained by GPS. The data exchange is carried out with the help of DSRC (Dedicated Short Range Communication). Due to information exchange, the motion parameters of both cars are known to each of them. The given algorithm fires every second upon arrival of a signal from the one’s car GPS receiver and data on the other car’s motion parameters as obtained via DSRC. The result of the calculations is the predicted minimal distance between the cars. Using these data the system produces a warning message for the car driver.
For vehicle-to-X communication it is necessary, that all participating parties agree on a common standard. The currently foreseen standard for this specific type of communication is IEEE 802.11p. Basically it is one amendment within the family of IEEE 802.11 standards that define the widely used technology for wireless local area networks (WLAN). IEEE 802.11p is adapted to the specifics that have to be respected in V2V (vehicle-to-vehicle) and V2I (vehicle-to-infrastructure) communications. In this case, the IEEE 802.11p standard defines the lower levels of the model OSI, including physical, and IEEE P1609 standart - the highest levels. The messages protocol for V2V communication sets the standard SAE J2735.
The prerequisite for the given algorithm’s operability is periodicity and reliability of information obtained through vehicle-to-vehicle communication. However, an urban environment provides many challenges for vehicle-to-vehicle communication. These include multiple propagation paths and many occlusions, particularly in areas where V2V messages would be most useful such as buildings, and others obstructions.
According to statistics driver error is the most frequent cause of accidents. One of the most dangerous places on the roads are the intersections without traffic light regulation. To prevent road traffic accidents on such intersections, we suggest the use of driver-warning systems based on exchange of information obtained through the GPS and the V2V and V2I data exchange systems.
This paper considers the possibilities of using the given algorithm under varying conditions both within and outside the boundaries of a populated area. 2. ALGORITHM APPLICATION FEASIBILITY CRITERION
The algorithm, which is presented in [6], provides for the use of road infrastructure. The given algorithm requires the use of a set of road traffic sensors, infrared transmitters and information and the V2I communication system. Besides, each motor vehicle must be equipped with an infrared signal receiver and a DSRC transceiver. Obviously, this algorithm may function on specially equipped intersections only.
978-3-902823-53-3/2013 © IFAC
One of the prerequisites of passing an intersection safely is the presence of only one vehicle at the intersection. So, on receipt of a possible collision warning signal, the driver must be able to bring his car to a halt before crossing the traffic lanes.
84
10.3182/20130925-3-CZ-3023.00019
IFAC PDeS 2013 Velke Karlovice, Czech Republic
Assuming proper operation of the brakes on the vehicle, the minimum stopping distance for a vehicle is determined by the effective coefficient of friction between the tires and the road, the driver's reaction time in a braking situation and the brake system’s reaction time.
The Graphs in Fig. 2 show the distance covered by a vehicle to a full halt versus the initial speed of the vehicle for various values of coefficient of friction between the tire tread and the road surface. For this purpose, the average time of driver’s reaction to the brake actuation is assumed to be 1.2 sec [2], and the braking system’s reaction time – 0.2 sec.
The friction force of the road must reduce vehicle’s speed to zero as shown in Fig. 1.
Fig. 1. Vehicle stopping distance. In order to stop a car, the kinetic energy must be reduced to zero or the kinetic energy must equal the energy given by the friction force [4] as shown in (1):
Ff d
mv 2
2 0
mgd ,
Fig. 2. Stopping distance/initial speed relationship for different µ values. It is obvious, that within the boundaries of a populated area, given the maximum allowed speed of 50 km/h, the minimum distance covered by a vehicle to a standstill under the worst conditions will be 44 m. Outside the boundaries of populated areas, given the maximum allowed speed of 90 km/h, the aforesaid parameter will increase to 114 m.
(1)
F f - friction force; m - vehicle’s mass; v0 vehicle’s initial speed; d - stopping distance; 2 g 9.8m / s ; - coefficient of friction between the tires where
Therefore, the prerequisite of using the proposed algorithm is the opportunity of receipt of a warning signal at least at 44 m to the intersection within the a populated area, and at least 114 m – outside its boundaries.
and the road. For calculating minimum stopping distance, a value of 0.8 is a nominal value for the coefficient of static friction between good tires and a good road surface. Almost always, coefficients of kinetic friction are less, and are dramatically less for wet, icy, slick, sandy, dirty very smooth or oily surfaces. It can be 0.7 or 0.6 for a vehicle with normally driven and worn tires. Poor condition tires might yield 0.5 or 0.4 for a closer representation of friction.
3. VEHICLE EQUIPMENT CONFIGURATION Two motor cars were used for test purposes; each of them was equipped with a system, whose structural scheme is given in Fig. 3.
Therefore, the distance covered by a transport vehicle to standstill may be expressed as (2):
d
(t dr
t br )v0
v02 , 2 g
(2)
where t dr - driver's reaction time; t br - braking system’s reaction time.
85
IFAC PDeS 2013 Velke Karlovice, Czech Republic
The ML5805 is a single chip fully integrated Frequency Shift Keyed (FSK) transceiver developed for a variety of applications operating in the 5.725GHz to 5.850GHz unlicensed ISM band. The transmit power of the transmitter is +21 dBm, and the receiver sensitivity is as good as that, namely, -97 dBm [5]. In ideal conditions, given there are no obstacles that could cause reflection, diffraction and dissipation, within line-ofsight between the transmitter and the receiver, the radio signal transmission losses for a definite frequency in free space may be expressed as follows (3):
PL
32.44 20 lg F0
20 lg D0 ,
(3)
Where PL - radio signal transmission losses (dBm), F0 carrier frequency of transmitted signal (MHz), D0 - distance between the transmitter and the receiver (km). Fig. 3. Structural flowchart of vehicle onboard equipment.
Thus, for the given parameters - PL not higher than 118
A GPS receiver GARMIN GPS-25LVC with an output in the NMEA 0183 format [3] provides the system with information about the current location, heading and speed of the car.
dBm, F0 = 5787,5 MHz, the maximum possible expected distance between the transmitter and the receiver must not exceed 3.6 km. Practically, the ideal situation upon which this equatation was derived is not realistic.
A 5.8 GHz DSRC transceiver shown in Fig. 4, based on a ML5805 microchip, enables the exchange of the obtained information with another transport vehicle.
The device has an omnidirectional, rooftop-mounted antenna as shown in Fig. 5. To exclude cable losses, the antenna must be connected directly to the high-frequency part of the transceiver.
Fig. 4. Onboard 5.8 GHz equipment. Fig. 5. Car with onboard equipment.
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IFAC PDeS 2013 Velke Karlovice, Czech Republic
Controller µC1 provides for data collection from the GPS receiver, data receipt and transmission to the transceiver and data transmission to the PC or CPU for processing. The transmitter units on both cars operate in a broadcast mode with the transmission periodicity of 1 sec. Such a periodicity depends on the updating frequency of data received from the GPS receiver output. The RMC (Recommended Minimum Specific GPS/TRANSIT Data ) command received from the GPS receiver contains a time marker, the vehicle’s latitude and longitude data, its speed and heading angle in relation to grid North. For over-the-air transmission, the given command is supplemented with a conditioning preamble, a synchronizing sequence and a checksum. Under broadcast data transfer operation, i.e. without acknowledging the receipt, the check sum enables evaluation of the reliability of the received data set, and the time marker enables to state the fact of any losses of transmitted data sets. For data set transmission, a high bit rate hardware port of a μC1 microcontroller is used. The info rate is 1.536 Mb/s. As a result, the transmission via a low bit rate port of a microcontroller to PC contains a time marker and information about the position, speed and heading angle of the two tested vehicles. Coordinates conversion and mathematical implementation of the algorithm of possible collision warning at an intersection are performed by a personal computer (PC).
Fig. 6. Road intersection with low-rise urban structures. Test drives 4 and 5 were conducted in the area of multi-storey buildings with extreme development density as shown in Fig.7.
4. TESTS RESULTS
During the test drive, one of the tested vehicles was in static position at various distances to a road intersection, while the second car was moving towards the intersection by crossing course.
The performed tests resulted in determination of the maximum possible ranges of reliable-service distances for various terrains, which confirms the feasibility of the use of the given algorithm for safe passage of a road intersection. Test drives were held in an urban territory with various types of buildings. Test drive Nr. 1 was conducted within line-ofsight between the transmitter and the receiver without any obstacles on the radio signal path. The results of Test drives 2 and 3 demonstrate the possibility of V2V communication in the area with two-three-storey buildings around the road intersection and with a low development density of the area as shown in Fig.6.
87
IFAC PDeS 2013 Velke Karlovice, Czech Republic
Fig. 8. Scheme of road intersection with distances. In conditions of direct visibility (test Nr.1) – absence of any constructions – the maximum distance between cars enabling information exchange is 495 m, which is equivalent to the distance of about 350 m to the intersection. In the given case, therefore, the use of the vehicle-to-vehicle communications system for safe crossroad passing will be possible even at the speed of 90 km/h, i.e. outside populated areas.
Fig. 7. Road intersection with multi-storied urban structures. The data obtained as a result of the performed tests are shown in Table 1: Table 1. Tests results Test Nr. 1 2 3 4 5
d1, m 350 80 80 60 15
d2, m 350 140 180 26 83
D, m 495 161 197 65 85
In conditions of low-rise urban structures (up to 3 storeys high), the maximum possible operable distance of the system is significantly lower, as shown in Table 1, tests Nr. 2 and Nr.3. That can be explained by the different conditions of radio-wave propagation, re-reflection and the low altitude of location of the transceiver antenna.
q, % 93 85 87 63 75
Nevertheless, the maximum distance from an intersection enabling information exchange is in the range of 80-180 m, which significantly exceeds the established criterion for an urban environment, i.e. 44 m.
Where d1 is the distance between the first (static) motor vehicle and the intersection, d2 – maximum distance between the second vehicle and the intersection, at the moment of receipt of the first data set, D – real maximum radio range as shown in Fig. 8.
In such a case, the number of correctly received data packets falls within the range of 87-93%, which, in view of the slow response of the motor vehicle, does not affect the system operability.
The q parameter estimates the ratio of the correctly received data sets number to the total number of data sets transmitted during the communications period. The number of data sets transmitted during the communications period is determined using time markers and the known transmission periodicity of 1s. The validity of the received data set is confirmed by a checksum.
The worst conditions for application of the given kind of vehicle-to-vehicle communications are observed in urban areas with multi-storied structures as shown in Table 1, tests Nr. 4 and Nr. 5.
88
IFAC PDeS 2013 Velke Karlovice, Czech Republic
In such cases, sustained exchange of information is only possible at 15-25 m to the intersection, which is insufficient according to the chosen speed criterion of 50 km/h. It is obviously impossible to apply the algorithm for safety passing of an intersection under the said conditions on the basis of vehicle-to-vehicle communications alone. The accomplished tests have shown that the presence of buildings and other obstacles significantly reduces the V2V communication rate in comparison with the estimated rate for free space. When comparing the test drive results with the aforesaid criteria, it becomes evident that the use of the proposed algorithm for safe passage of an unsignalled intersection is feasible under the conditions of line-of-sight and low-storey development. In conditions of multi-storey urban development, it is impossible to use vehicle-to-vehicle communication alone for intersection passage safety purposes. In the given case, it is worthwhile applying algorithms based on an integrated use of the V2V and V2I communication systems. 6. CONCLUSIONS The present paper provides the feasibility criteria for the application of the algorithm for safe passage of an unsignaled intersection using the vehicle-to-vehicle communication system only. On the basis of the results of the performed tests, we have assessed the system feasibility and made conclusions on the system applicability under varying conditions both within and outside the boundaries of a populated area. Further possibility research of applying of the algorithm provide for tests for moving cars, as well as increasing the vehicles involved in the tests. REFERENCES Ahrems J., Algorithm for determination of safety intersections. In Proc. 13th Biennial Baltic Electronics Conference (BEC2012), Tallinn, Estonia, 2012, pp.175178. Mehmood A., Easa S. M., Modeling Reaction Time in CarFollowing Behaviour Based on Human Factor. International Journal of Engineering and Applied Sciences. 5:2 2009, pp. 93-101. NMEA 0183 Standard for Interfacing Marine Electronics Devices, Revision 3.01, NMEA Standard 0183, 2000. RF Microdevice Data Manual, RFMD Inc., 2008. Popescu-Zeletin R., Radusch I., Rigani M. A., Vehicular-2-X Communication. Springer-Verlag, Berlin, 2010. RFMD Inc., RF Microdevice Data Manual, RFMD Inc., 2008. Tsukada N., Yamada K., Takahashi S., Development of Driving Safety Support Systems for Non-right-of-way Vehicles at Unsignalized Intersection. 19th ITS World Congress, Vienna, Austria, 22/26 October 2012.
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