OIML R 91
version 2014
Radar equipment for the measurement of the speed of vehicles
t.janssen
1-2-2014
Radar equipment for the measurement of the speed of vehicles
( with or without recording devices )
draft version February 2014
1. SCOPE
This Recommendation is applicable to microwave radar equipment for the
measurement of at least traffic speed on roads and distance and angle when
required to optimize the use of the radar, hereafter, in short, “radar”. The
Recommendation states the conditions that the radar must satisfy when the
results of measurements are to be used in legal proceedings. The legal
interpretation of the results of measurements, the choice of radar types and
techniques and the conditions under which these instruments may be applied
are left to national regulations.
2. RULES OF CORRECT OPERATION
2.1 Handbook ( see point 4 )
Radar systems shall be installed and used in accordance with the instructions of
a handbook issued by the manufacturer and approved with the instrument, at
the time of the pattern approval
2.2 Certainty of vehicle identification
The construction of the radar system , including the internal logic of the
measurement process, shall ensure that, when the instrument is used in
accordance with the handbook, an indicated speed and all other relevant
information cannot be attributed to the wrong vehicle even where vehicles are
passing or overtaking, or when the radar is mounted in a moving vehicle.
The radar system shall have a direction discriminator. However, because of its
limited effect, a direction discriminator does not always offer a complete
solution and additional means shall be used to ensure correct operation. With
current technology, such as irregular signal discrimination, tracking radar,
vehicle identification is possible even in dense traffic. Where there is no other
solution the radar system shall invalidate its own result when two or more
vehicles with different speeds pass simultaneously through the radar beam
unless the radar system is capable of measuring multiple vehicle separately at
the same time. The radar shall be equipped in such a way that no
Update OIML R91 version February 2014 TMJ
Page 2
misunderstanding can arise in relation to the indicated or recorded
measurement value(s).
2.3 Aiming device
If the radar speed meter shall be deployed at a fixed measurement angle,
then the radar system shall be fitted with an aiming device. The relative
error of measurement attributable to misalignment of the aiming device
shall not be greater than 0.5% of the angle of measurement or 0.3 %of the
actual speed. The aiming device may be omitted if the radar system is to be
used with a beam that is practically parallel to the direction of traffic
movement ( angle of incidence not exceeding 10 degrees ) or when the
radar system is capable of automatically correcting the measurement angle
of the measured vehicle.
2.4
Radiation pattern of antenna
The approval of a given angle of incidence is left to the national regulations.
For beam axes not parallel to the direction of traffic movement, angles of 15
to 30 degrees are recommended or automatic compensation of the angle of
incidence of the measured vehicle can be used to ensure correct speed
measurements of up to but not limited to four lanes of traffic.
The handbook shall give details for positioning and adjustment of the aiming
device, for all foreseeable installations ( roadside, bridges, gantries, patrol
cars, etc… )
Using multiple antenna structures and an appropriate modulation of the
radar transmission can allow measurements of vehicles over much wider
area, both in range and angle. The radiation pattern used may then cover a
significant wider area then described above. In this case provision shall be
made to prevent indications from locations in the radiation pattern in which
the position information is unreliable.
When the radar is installed and used in accordance with the handbook, no
measurement shall be possible in those parts of the antenna beam where an
incorrect angle of incidence may result in relative speed measurement error
greater than +/- 2% . Errors resulting from tilting of the radar in relation to
the surface of the road shall also be considered.
Update OIML R91 version February 2014 TMJ
Page 3
Note: This requirement may be satisfied by signal processing or by special
shaping of the radiation pattern using the latest available technologies.
2.5
Time span for speed indication
If it is possible to use the radar system without a suitable recording device (
see point 2.6 ), the visual indication of speed shall remain visible and shall
inhibit any further measurements until it is freed by a positive action. No
event or action during this time may influence the result or have any effect
on subsequent measurements. These requirements do not apply to results
below a given speed limit.
2.6 Recording devices
If an ( image ) recording device records the result of the radar speed
measurement, then the record shall indicate at least the vehicle whose
speed is measured, date and time of the measurement, the measured speed
and vehicles direction of travel, the measurement location, the sensitivity of
the radar speed meter, if this is variable, serial number of radar system,etc.
If a camera is used , the correct relationship between the direction of
radiation and that of the optical axis of the camera shall be ensured by
mechanical set up or by operations described in the handbook by which the
correct aiming of the system is verified by other means such as the resulting
picture, template. etc…
2.7
Attended radar ( stationary measurement )
For attended use of a radar system the same specifications as for
unattended radar systems in point 2.8 shall comply, but without the use of
a recording device.
2.8
Automatic and unattended radar ( stationary measurement )
Radar systems designed for operation under circumstances where it is not
possible for an operator to verify continuously their satisfactory
performance shall provide a level of confidence “near to certainty” that the
error of each measured result shall be within the permissible limits. The
measurement set up shall have such properties that it can be established
with certainty by means of the recording to which vehicle the measured
speed relates, irrespective of the number and type of vehicles on the road
Update OIML R91 version February 2014 TMJ
Page 4
section where the measurements are carried out. The certainty of the said
recording shall be at least equivalent to that obtained if a second
measurement is available, obtained by means of a different, independent
measurement method whose measurement error is not greater than 10% of
the actual speed measurement. If this condition cannot be met, the invalidity
of the measurement result shall be unequivocally indicated by the
measurement instrument on the image recording device, or the
measurement result shall be eliminated.
Note: The automatic checking of the instrument’s essential operation is
advised in point ….of this Recommendation. Furthermore, with such
unattended operation it is strongly advised that redundant measurement
techniques such as, for example, taking two pictures of the offending vehicle
separated by a specified time interval or distance interval to be used.
Another option could be to use one or two still images and/or a short (
sequential) video clip to achieve an independent method of checking the
original speed measurement by the radar system.
2.9
Mobile radar speed meters
Should we include an extra point for the mobile measurements with radar
system installed in a moving vehicle and using the own speed of the vehicle
and the measured speed of the overtaking or passing vehicle with a radar
system??
2.10 Automatic exclusion of inaccurate power supply
Speed measurements shall be inhibited when the power voltage and
temperature varies beyond the specified limits.
2.11 Overall functional test
The radar shall incorporate an internal test generator of simulating a
measurement for the purpose of verifying the correct operation of the radar
system, that is independent of the measuring circuits, and by which, at
switch-on and additionally at operator’s will, ( or automatically??) the
instrument is checked overall. Its test signal is introduced as early as possible
into the signal chain following the microwave circuits and shall check at least
every non intermittent failure of the low frequency and result handling
circuits, including circuits necessary for the functioning and accuracy of the
speed indication. Records shall confirm that these tests have been
Update OIML R91 version February 2014 TMJ
Page 5
performed successfully. The manufacturer shall provide an internal
simulation device which enables the operator to perform this test.
( which parameter for a failure of test ?? )
The manufacturer shall provide a simulation/test input which enables
metrological tests to be performed in a laboratory for pattern approval. It
must be possible to measure the accuracy of the speeds simulated by this
device and it must be as accurate as possible to meet the national
regulations.
3 CONSTRUCTION
3.1 Speed indicator and speed range
In radar systems useable without data recording the (speed) indicators shall be
readable by two operators simultaneously in ambient conditions corresponding
to the conditions of use for which the instrument is suitable according the
handbook.
The speed range shall include at least the range 30 – 150 km/h (20 -250 km/h
or 10 – 156 mph ??)
3.2 Mechanical strength
The instrument must be well and solidly built. The materials used must
guarantee sufficient strength, stability, resistance and consistency for normal
operational use and shall meet the national legislation.
3.3 Resistance to extremes of climate
3.3.1 Operational temperature
The manufacturer must indicate the ambient temperature limits within the
radar system can be operated in compliance with the requirements of the
national legislation. When these temperature limits are exceeded ,instruments
designed for automatically/unattended operation shall automatically go out of
enforcement/ operation. These temperatures must be a minimum of -10 to +
50 degrees Celsius.
3.3.2 Storage temperature
When out of service or in storage the radar system shall be capable of
withstanding ambient temperatures of -25 to + 85 degrees Celsius
Update OIML R91 version February 2014 TMJ
Page 6
3.3.3 Relative humidity
The radar system shall be resistant to relative humidity of 95% - non
condensing of the ambient air, both under operational ( see point 3.3.1 ) and
storage conditions ( see 3.3.2 )
3.3.4 Weather resistant
The parts of the radar system that are exposed to the weather shall be
protected against dust and water spray when all the accessories are fitted.
3.5 Reliability of electronic and logical components
3.5.1 Reaction to disturbance
Radars shall undergo test showing their reactions to:
To be supplied by Ambler Thompson
3.5.2 Protection against electronic failure
3.5.2.1 Discontinued ( digital ) signals
The reliability of the results produced by ( digital ) signals such as transfers,
storage, indications, etc. must be guaranteed, either individually ( step by step )
or in blocks( global ), using redundant operations for software monitoring or
equivalent procedure to ensure correct operation. Each fault in the consistency
of the operations shall inhibit further measurements.
Elements and components used in such operation ( program memories,
transfer memories, processors, cabling, indicators, etc.. ) shall be checked at
least every time the equipment is switched on, by special checking operations,
unless they are checked automatically by the logical measures as mentioned
above.
Errors shall be clearly indicated and the handbook shall explain the measures to
be taken.
3.5.2.2 Software programs faults
Should we use OIML guidelines and also parts of Welmec 7.2
To be supplied by Roman Flegar
Update OIML R91 version February 2014 TMJ
Page 7
3.5.2.3 Continuous signals ( analogue signals )
3.5.2.3.1
Microwave circuitry shall ensure a long term stability of tuning over at least 2
years of approximately +/- 0.2 % in frequency.
If the radar transmission is modulated then the short term stability and
accuracy of such modulation may have a profound effect both on the accuracy
of speed measurements and on the certainty of vehicle identification. The
realization of the microwave circuits must be such that the limits of speed
accuracy and certainty of vehicle identification set out in the user handbook
are realizable in the intended environments. Typically this is achieved by
associating the main frequency microwave generator with a separate fixed
frequency oscillator circuit of significant higher stability, such that its stability
can be in part, impressed upon the main microwave generator. A Phase Locked
Loop ( PLL ) is an example of such an association.
3.5.2.3.2
The gain of analogue channels shall have no influence on results, or its effect
shall be periodically checked conform national legislation.
4.0 Handbook
The manufacturer shall provide each radar system with a handbook which shall
be approved at the same time as the pattern approval. This handbook shall
contain at least:
-
The theory of operation of the equipment
Installation/set-up instructions
An explanation of the general lay out ( operation schematic )
Detailed specifications of normal operating conditions
Operation modes
Information of the main causes/sources of errors
An overview of the influence quantities affecting the measurement, and
of the partial errors they may introduce.
5.0 Protection against tampering
It shall be possible to seal or otherwise protect the radar system in such a way
that those parts which, if tampered with, could lead to errors in measurements
or metrological unreliable operation.
Update OIML R91 version February 2014 TMJ
Page 8
6.0 Identification of the equipment
The radar system and each separately housed sub unit shall carry, in indelible
lettering at least the following information:
- the name( or trade mark ) and address of the manufacturer or his
representative
- the type indication and serial number of the radar system
- year of construction
- the unit in which the measured variable is expressed
- the measurement speed range
- type approval number, if applicable
or all information as required by national legislation.
7.0
Pattern approval
7.1.1 Test conditions
Reference value
Ambient temperature
Ambient humidity
Power voltage
Frequency
range
+20⁰ C
-10⁰ C to + 50⁰ C
60%
nominal
nominal
either value, non-condensing
-10%,+20% of nominal
nominal +/- 3 % ??
Radars shall be tested at +20⁰ C and at the minimum and maximum
temperature, or as specified by the manufacturer, with different power
voltages; humidity and power frequency shall be varied only if they have a
noticeable influence.
For each factor mentioned above, its variation throughout the whole defined
range shall not induce a change of indication greater than 50% of the moduli of
the maximum permissible errors given in point 7.1.2 and 7.1.3.
7.1.2 Testing of micro wave section
Radiation pattern and power limitations
Aiming device
Frequency range and oscillator stability
conform point 2.4 shall apply
conform point 2.3 shall apply
conform national legislation
Note: Pattern approval is also dependent of certification by the authority for
communication equipment
Update OIML R91 version February 2014 TMJ
Page 9
7.1.3 Testing of the low frequency section
7.1.3.1 Doppler radars
For Doppler radar the frequency fd of the simulated Doppler signal the
theoretical speed indication shall be computed from:
Vd = 0.5 x fd x ( λ/cos α )
Where: λ = the emitted wave length
Α = the average effective angle of incidence
7.1.3.2 Modulated radars
For all other type of radars, used this should be discussed and see also point 2.9
Proposed text could be:
The general required specifications as under points ….. ….. shall be deemed to
be met with regards to the width of the radar beam if the proportion of the
maximum error which is dependent on the size of the half value angle does not
exceed 2.5% of the actual speed. With regard to the effect of secondary
maxima of the antenna characteristics, the secondary maxima and also the
main maximum and the maxima at the other frequencies after reception of the
transmitted signal have a power ratio of at least 30 dB.
7.1.3.3 Maximum error
The maximum error under laboratory research shall not exceed 1 km/h for
simulated speeds not greater than 100 km/h and 1% of the simulated for
speeds greater than 100 km/h. Speed simulation shall be carried out by
simulating a singular point that moves at a uniform speed along a straight line
through (the centre) of the antenna. The simulated speed corresponds to this
uniform speed multiplied by the cosine of the measurement angle , if
applicable. Should measured value be rounded up / down or truncated???
7.2 Tests of effects of influence factors and disturbances
The tests that shall be performed and the criteria of acceptance are described
in xxxxxx and not clear to me at the moment who is responsible for this part.
Probably the existing Annex in OIML R91 which refers to D11 can be used for a
major part.
Update OIML R91 version February 2014 TMJ
Page 10
7.3 Metrological field tests.
To be performed after all laboratory tests have been completed????
Information to be supplied by Walter Fasel
7.4 Conformity to approved pattern
The approved pattern is defined by the instrument’s characteristics
determining metrological integrity and conform the specifications of this
document.
A test/approval certificate shall be issued by the certifying institute on the
basis of an examination conducted by that institute. This examination shall
investigate those aspects that are crucial to the suitability of the radar speed
system with or without a recording device. This document shall describe at
least used equipment and calibration dates, test set up, method of testing and
applied standards and results , etc …
Update OIML R91 version February 2014 TMJ
Page 11
Update OIML R91 version February 2014 TMJ
Page 12