The Collision Avoidance System Using the Doppler Effectbetween Vehicles in the intersection
Kosuke Tomoyama1, Takeshi Hattori1, and Ikuko Yairi1
11.

Department of Electrical and Electronics Engineering, Sophia UniversityIntroduction

The speed of the target car is estimated from theRecently, although the road traffic plays an important

Doppler frequency which is demanded.

role in today’s social system, a present automobilef D v1 cos 1＋v2 cos  2

(3)happening, but also to avoid traffic accident. In thisf    v1 cos 1v2  D
(4)cos  2
v1 ：Speed of the observation car(m/s)
v 2 ：Speed of the target car(m/s)
1 ：Output angle degree from the target car (°)
 2 ：Arrival angle to the observation car (°)

paper, we construct systems preventing a traffic

The speed of the observation car is known andaccident between the vehicles by the wirelesssupposes that it can acquire the position of it from GPS.

communication.

It can count the position of the target car backward

2.

from it of the observation car and the arrival time fortraffic has various problems such as traffic accident andtraffic jam. Therefore Intelligent Transport System(ITS) is researched actively to aim at the effective
service and the security of the vehicle, but the present
conditions of traffic accidents are still serious, so it isnecessary not only to investigate the accident after

The proposed method

We discuss a system which can detect a car existing inpath. In addition, the path to discuss uses the property

the blind spot only by observation car without using thethat is the reflection wave. Then we can lead the arrival

infrastructure such as roadside units using radio waves.

angle to the observation car and demand the speed ofAt that time, it installs “ Radio Wave Mirror” in thethe target car.

crossing center in order not to depend on the3.

environment around the crossing. Through RadioWe analyze the radio wave propagation situation in

Wave Mirror we identify the reflection wave that seems

the assumption accident scene at the crossing by theto communicate with a car existing in the blind spot.

simulation software (Raplab) with ray tracing. In thatWe estimate the speed of a target car existing in thecase, we assume to use that the transmitting antenna is

blind spot using the Doppler Effect based on the pathstandard dipole antenna and the receiving antenna iswhich is identified.

array antennas. [1] The speed of each cars is assumed tov l(1)tf D v

(2)System models and Simulation

be constant.
Thispaper

assumes

intersection

environment

f D ：Doppler frequency (Hz)  ：Wavelength(m)described in Fig 1, Radio Wave Mirror Model describedl ：Path length(m) t ：Time(s)in Fig 2, and Intersection of Raplab Model described inFig3. Table 1 and Table 2 contain a summary of thesimulation parameter setting. Fig 4 shows Image of ray
tracing in this simulation and the target path.

Table 2.Materials Parameter
Materials

The path

Dielectric

Conductivity[S/m]Constant [F/m]to discuss is involved in only the target car existing in

metal

8.85 ×10-12

5.76 ×10+6

the blind spot, the observation car, and Radio Wave

concrete

5.99×10-11

2.30×10-3

mirror. From the path, the speed of the target car isestimated using (2) and (4).Fig 5 shows the graphwhich compared the theoretical value which theestimated result.

Fig 4.Image of Ray tracing in This Simulation
And The Target Path

Fig 1.Intersection Model

Fig 5. Estimated and Theoretical value
4.
Fig 2.Radio Wave Mirror ModelConclusion

From this discussion, if we were able to acquire
observation car positional information with GPS and an
arrival angle in the crossing model which installed
Radio Wave Mirror, the speed of the target car isestimated correctly by using the Doppler effect of radio
wave. That is, it is possible to detect a target car
existing in the blind spot only by one observation car

Fig3.Intersection of Raplab Model

without depending on the environment around theTable 1.System Parametercrossing. Also, Future problems include the furtherTransmission Power(W)0.01

effectiveness of the suggestion method by the estimate

Carrier Frequency(MHz)700of the arrival angle, evaluations in more detailed

Height of Transmission and Reception(m)0.2

propagation environment.

Speed of the observation car(m/s)

105.

References

Speed of the target car(m/s)

12.5

[1]

Nobuyoshi

Kikuma,“ADAPTIVE

SIGNALPROCESSING with Array Antenna” in Japanese, 1999 byScience and Technology Publishing Company, Inc.