Traffic monitoring device

A traffic monitoring device mounted in a moving monitoring vehicle comprises a radar device for measuring the relative speed of a vehicle to be detected with respect to the speed of the monitoring vehicle. A speedometer measures the speed of the monitoring vehicle. By means of a releasing mechanism automatically triggered at adjustable limit speeds, a camera is released and the vehicle to be detected is photographed. The relative speed of the vehicle to be detected and the speed of the monitoring device are added in summing means. The sum then corresponds to the absolute speed of the vehicle to be detected. The camera is not released dependent on the relative speed but on the absolute speed of the vehicle to be detected. Thereby, all vehicles exceeding an allowed speed are detected without taking an unnecessary number of pictures.

TECHNICAL FIELD 
The invention relates to a traffic monitoring device particularly for 
application in a moving monitoring vehicle, comprising 
a measuring instrument, for example a radar instrument, for measuring the 
relative speed of a vehicle to be detected with respect to the speed of 
the monitoring vehicle, 
speed measuring means for measuring the speed of the monitoring vehicle, 
recording means for recording the vehicle to be detected, and 
releasing means automatically releasable at adjustable limit speeds for 
releasing the recording means. 
Thereby photographic documentation can be prepared which shall serve as 
evidence of violation of traffic regulations. 
BACKGROUND ART 
It is well known that the driving speed of a vehicle can be measured by 
means of a stationary radar device and that a radar controlled indication 
device can be photographed together with the vehicle. 
Because it, as a rule, is necessary to release monitoring pictures manually 
or by means of telecontrol, it is known that electromagnetic releasing 
means for the shutters exist. 
Also, monitoring vehicles are used for traffic monitoring. From German 
Patent No. 1,139,315 it is known that the monitoring vehicle follows a 
vehicle with the same speed and prepares a documentary evidence of a 
vehicle exceeding the allowed speed by means of photographing the vehicle 
and the speedometer serving as vehicle speed indicator, together with 
photographically documenting the time and date. 
From U.S. Pat. No. 3,206,748 a photographic traffic monitoring device is 
known, which is adapted to optionally determine the speed of a vehicle to 
be monitored by following it or by stationary operation by means of radar. 
In the brochure TRAFFIPAX-micro speed of the company Traffipax-Vertrieb, 
Hildener Stra.beta.e 57, 4000 Dusseldorf 13, a traffic radar device is 
described, which likewise is adapted for mobile and stationary operation. 
The device is pivotable such that the traffic monitoring in the stationary 
operation can be achieved optionally from the left or the right side of 
the road. The traffic moving away or the approaching traffic can 
optionally be measured and photographically documented. In stationary 
operation, separately adjustable limit speeds are provided for passenger 
cars and motor lorries during monitoring the traffic moving away. The 
traffic radar device is adapted to be optionally mounted in patrol cars 
having fixedly mounted support for radar antenna or for mounting the radar 
antenna on a stand. In suitable vehicles the antenna can be mounted 
invisibly behind the grille and remain there during travel. For mobile 
operation the device is provided with an electronic speedometer having 
digital display. The speedometer is switched-on automatically as soon as 
the radar device is switched-off. Through corresponding signs at the 
prepared photo it can be seen whether the device has been operated with 
radar or with speedometer. 
It is disadvantageous if the monitoring vehicle has to be driven with the 
same speed in the required proximity behind the vehicle to be detected, 
because it easily can be recognized as a police vehicle. In the brochure 
GATSO-meter of the company Gatsometer B.V., Tetterodeweg 10, 2050 AA 
Overveen, a device is mentioned, which likewise is adapted to be used in 
mobile or stationary operation. With this device it is furthermore 
possible to use the radar monitoring and the speedometer monitoring in a 
way that the monitoring vehicle is driven a at constant speed but more 
slowly than the vehicle to be detected. The speed of the monitoring 
vehicle and the relative speed, as measured by the radar device of the 
vehicle to be detected with respect to the speed of the monitoring 
vehicle, are reflected in a photographic picture of the vehicle to be 
detected. 
In order to obtain evidence as irrefutable as possible, further data, e.g. 
date and time, are reflected in the picture. 
The prior art traffic monitoring device of the above mentioned type, which 
is mounted in a monitoring vehicle and which serves to monitor the speed, 
is ineffective. On one hand, the monitoring vehicle has to be driven at 
constant speed and thus cannot be adapted to the given traffic. On the 
other hand, too many or too few pictures are taken, which means that 
vehicles driven too fast are possibly not detected and vehicles are 
photographed, which do not exceed the allowed speed. This is the case, for 
example, when the monitoring vehicle is, in fact, driven at constant speed 
but too fast. Exceeding the allowed speed is partly not recorded, because 
the radar device does not measure any exceeded speed. When the monitoring 
vehicle is driven too slowly, the device signals that the allowed speed 
was exceeded, which actually is not the case. The camera is released and a 
picture is taken, in which it later can be seen that the allowed speed. 
DISCLOSURE OF INVENTION 
It is the object of the invention to provide a traffic monitoring device of 
the above defined type wherein the monitoring vehicle speed can be adapted 
to the given traffic flow and that every vehicle exceeding a maximally 
allowed speed also is detected without taking unnecessary pictures. 
According to the invention this object is achieved in that 
summing means are provided, to which the relative speed of the vehicle to 
be detected and the speed of the monitoring vehicle are applied, and which 
supplies a corresponding sum value thus corresponding to the absolute 
speed of the vehicle to be detected, and 
the releasing means of the camera are triggered depending on this sum value 
when the sum value exceeds a determined adjustable limit speed. 
Therewith the recording means are released dependent on the absolute speed 
of the vehicle to be detected and not dependent on the relative speed of 
the vehicle to be detected with respect to the monitoring vehicle. 
Embodiments of the invention will now be described in greater detail with 
reference to the accompanying drawings.

BEST MODE OF CARRYING OUT THE INVENTION 
In FIG. 1 a usual traffic situation, for example on a freeway, is 
illustrated. A monitoring vehicle 10 is driven in the right-hand lane and 
is passed by a vehicle 12 to be detected. 
In FIG. 2 a traffic monitoring device according to the invention is 
illustrated by a block diagram. A radar device 14 measures the relative 
speed of the vehicle 12 to be detected with respect to the monitoring 
vehicle 10 and supplies a corresponding signal. In order to measure the 
speed of the monitoring vehicle 10, it is provided with speed measuring 
means 16, for example a speedometer, which likewise supplies a 
corresponding signal. Recording means 18 serve to record the vehicle 12 to 
be detected. The recording means 18 are released by releasing means 20 
automatically releasable at adjusted limit speeds. Through a line 24 the 
signal from the radar device 14, and through a line 26, the signal from 
the speed measuring means 16 are applied to summing means 22. The summing 
means 22 supply a signal corresponding to the sum of the two speeds. This 
sum corresponds to the absolute speed of the vehicle 12 to be detected. 
This signal is applied to comparison means 30 through a line 28. In the 
comparison means 30 the absolute speed of the vehicle 12 to be detected is 
compared with a limit value adapted to be input. If the absolute speed of 
the vehicle 12 to be detected exceeds the input limit value, the 
comparison means 30 supply a signal to the releasing means 20 through a 
line 32. 
The signal from the radar device 14 is likewise applied to comparison means 
34, which supply a signal through a line 36 to stop means 38 for the 
releasing means 20 if the relative speed measured with the radar device 14 
of the vehicle 12 to be detected drops below a limit value adapted to be 
input in the comparison means 34. 
The signal from the speed measuring means 16 is likewise applied to 
comparison means 40, which supply a signal through a line 42 to stop means 
44 for the releasing means 20 if the speed of the monitoring vehicle 10 
measured by the speed measuring means 16 drops below a lower limit value 
input in the comparison means 40. 
In order to control the speed of the monitoring vehicle, warning means 46 
are coupled to the comparison means 40. The warning means 46 supply an 
acoustic and/or optical signal to the driver if the monitoring vehicle 10 
drops below or exceeds the lower or upper limit values input in the 
comparison means 40. Furthermore, or as an alternative thereto, a speed 
controller (not illustrated in FIG. 1) adapted to be switched-on and -off 
can be provided, by means of which the speed of the monitoring vehicle 10 
automatically is kept between the limit values input in the comparison 
means 40. 
The speed signals from the radar device 14, from the speed measuring means 
16 and from the summing means 22 are applied through lines 48, 50 and 52, 
respectively, to digital indication means 54, which are described 
hereinbelow in greater detail with reference to FIG. 3. The indication 
means 54 comprise at least one display 56 of the relative speed of the 
vehicle 12 to be detected, one display 58 of the speed of the monitoring 
vehicle 10 and one display 60 of the absolute speed of the vehicle 12 to 
be detected. 
The automation of the releasing means 20 in response to a signal sent to 
the releasing means 20 from controlled controlled by, the comparison means 
30, 34 and 40, can be switched-off. For example switches 62, 66 and 70 and 
push-buttons 64, 68, 72 and 74 are provided to this end. Hereby the 
recording means can be released manually when the monitoring vehicle, for 
example, is driven at the same speed behind the vehicle to be detected. 
Thereby it is also possible to park the monitoring vehicle 10 on the 
roadside and to use the traffic monitoring device as a stationary radar 
device. To this end the traffic monitoring device has to be adjustable in 
several defined positions relative to the monitoring vehicle 10. To this 
end the traffic monitoring device is pivotable and arranged to be stopped 
in several positions. With regard to other details these manners of 
traffic monitoring are known and not described in greater detail herein. 
As indicated by broken lines in FIG. 2, the relative and absolute speeds of 
the vehicle 12 to be detected and the speed of the monitoring vehicle 10 
are recorded on the picture achieved by means of the recording means 18. 
In FIG. 3 an embodiment of the indication means 54 is illustrated 
schematically. For example, the upper display 58 indicates the speed of 
the monitoring vehicle 10, the middle display 56 indicates the relative 
speed and the lower display 60 indicates the absolute speed of the vehicle 
12 to be detected. Numeral 76 indicates a further display, in which 
further information, e.g. time information, adjustable by means of control 
keys 78 is illustrated. Such displays are already used in typical traffic 
monitoring devices and thus are not described in greater detail herein. 
The recording means 18 are preferably a photographic camera for preparing a 
photographic documentation 80 of the vehicle 12 to be detected. Such a 
documentation 80 is illustrated in FIG. 4. The indication means 54 are 
reflected into the photographic documentation 80 and the instantaneous 
mode of operation of the traffic monitoring device is indicated. However, 
it is also possible to record the information on the film rim. 
The described arrangement operates as follows: 
A lower limit value is input in the comparison means 34 for the speed of 
the vehicle to be detected measured by means of the radar device 14. This 
limit value depends on the range of accuracy of the radar device 14 and 
shall be 20 km/h in the numerical example set forth herein. 
A lower and an upper limit value are input in the comparison means 40 for 
the speed of the monitoring vehicle 10 measured by means of the speed 
measuring means 16. The lower limit value depends on the range of accuracy 
of the speed measuring means 16 and shall be 25 km/h herein. The upper 
limit value depends on the maximally allowed speed at the road section in 
question and on the lower limit value for the speed measured by means of 
the radar device 14. This upper limit value is obtained by subtracting the 
lower limit value for the speed measured by means of the radar device 14 
from the maximally allowed speed. In the numerical example performed 
herein it is assumed that the maximally allowed speed is 100 km/h. 
Accordingly the upper limit value of the comparison means 40 is 80 km/h 
(100 km/h-20 km/h=80 km/h). 
A limit value is likewise input in the comparison means 30 for the absolute 
speed of the vehicle 12 to be detected and obtained by means of the 
summing means 22. This limit value corresponds to the maximally allowed 
speed and is thus 100 km/h. 
When the monitoring vehicle 10 is passed by a vehicle 12, the speed of this 
vehicle 12 is measured by means of the radar device 14. Only when the 
speed of the vehicle 12 exceeds the maximally allowed speed of 100 km/h, 
for example, 120 km/h, a releasing signal is applied from the comparison 
means 30 to the releasing means 20 whereby the recording means 18 are 
released. For example, a photographic documentation 80 of the vehicle 12 
to be detected is prepared. By means of suitable optical systems, and 
suitable arrangement of the radar device 14 and the recording means 18, it 
is ensured that the vehicle 12 and the license number 82 of the vehicle 12 
can be clearly ascertained and that the vehicle 12 is centrally in the 
documentation 80. The indication means 54 with the corresponding data (see 
FIG. 1) are reflected in the documentation 80 and are also seen therein. 
Therefore, the indicated relative speed of the vehicle 12 to be detected 
and the indicated speed of the monitoring vehicle 10 do not just serve as 
information but also for checking the calculated absolute speed of the 
vehicle 12 to be detected. 
When the monitoring device 10 is driven more slowly than the lower limit 
speed of 25 km/h input in the comparison means 40, such that the speed 
measuring means 16 supply a value which is too inexact, the comparison 
means 40 apply a blocking signal to the releasing means 20 and blocks the 
releasing means 20. When the monitoring vehicle 10 is driven faster than 
the upper limit speed of 80 km/h input in the comparison means 40, for 
example 95 km/h, the vehicle 12 driven at a speed between 100 km/h and 115 
km/h are not detected, which is undesirable. In order to avoid the problem 
with dropping below or exceeding the limit values, the comparison means 40 
are coupled with warning means which supply a signal to the driver when 
the limit values are fallen below or exceeded, respectively. 
Furthermore, a speed controller can be provided, by means of which the 
speed of the monitoring vehicle 10 automatically can be kept between the 
limit values input in the comparison means 40. 
Thus, with this traffic monitoring device, all vehicles exceeding a 
maximally allowed speed are detected without taking too many pictures. The 
monitoring vehicle 10 need not be driven at a predetermined constant 
speed, and it can travel along with the normally varying traffic flow.