Metrological Field Test Requirements
Version 3 modified 12/05/2014 with French comments
Requirement to the measurement uncertainty
The maximum permitted error of the DUT must fulfil the following requirements under worst
case traffic condition. These tests must be performed with real traffic on different roads and
can be associated with artificial signals simulated in laboratory. The influence factors and
disturbances (temperature, humidity, chocks, vibration, EMC…) must be checked in
laboratory under speed simulation condition (see test procedure chapter)..
Tests shall be covered all aspects, which are important for the DUT (depend of the
measurement technology):
 Installation conditions
o Geometric parameter to the measurement situation (installation height,
distance to lane and vehicle, different angles etc.);
o User influence;
o etc.
 Driving and traffic conditions
o Vehicles categories;
o Driving directions and lanes;
o Diagonal drive;
o Driving along curves;
o Braking and accelerating manoeuvres;
o Traffic density;
o Vehicle oscillation (step measurement error);
o Influence of reflection from the crash barrier or other objects;
o Multivehicle situations;
o etc.;
 Environmental conditions
o Weather;
o Contaminated sensors;
o Partial shadow;
o etc.
Comment: Measuring devices used to monitor speed must exhibit high dependability to achieve
credibility. Police, courts of law and naturally road users, too, must be able to 100 % rely on the
measured values. Ensuring this is the job of a type approval authority. A measurement made in road
traffic cannot be repeated. It must be accurate and dependable the first time and that even if the traffic
is dense and the measuring situation complex. These are the reasons for the above strong
requirements:
French Comment : the evaluation criteria during influence factors and disturbances laboratory tests
must be defined in the test procedure chapter (MPE compliance during influence factors tests, no
significant fault during or after disturbance…)
Error limits:
Single values
No error of indication beyond the MPE(+/-3 km/h up to 100
km/h and>= +/- 3 % above 100 km/h. These MPE are doubled for in motion speedmeters );
Remarks:
Absolute limits under worst condition!
Standard Deviation ()
< 0.6 km/h (< 0.6 %) for speed value rounded to one decimal
place [recommended for type examination].
< 0.8 km/h (< 0.8 %) with truncate decimal places of speed
value;
Remarks:
PS: The standard deviation depends of the speed sensor technologies
the vehicles categories, and varies from lower to higher speed.
The check (on the road and in laboratory simulation) should be made
with a sample of 500 vehicles with a useful vehicles categories
distribution
Mean Deviation ()
5 <= (3 km/h – ) /, 5 <= (3 % – ) /
±1 km/h (±1 %) for speed value rounded to one decimal place
-1.5 km/h <=  <= 0.5 km/h (-1.5 % <=  <= 0.5 %) with
truncate decimal places of speed value
Remarks:
PS: needs a cosine factor correction!
French Comment :We only use the criteria on single values in France. The mean and standard
deviation criteria have to be analyzed to check if these requirements are fulfilled by instruments ever
approved in France. The implementation of such criteria (standard deviation and mean deviation)
should be further discussed with other countries. If there is a consensus to implement these criteria,
we think as a first step that a criterion based on mean deviation +/- 3 standard deviation compared
with MPE should be sufficient (for example and with speed <= 100 km/h : +3 <= 3 and –3 <= -
3).
Size of sample
Min. 500 measurements for each speed direction.
Additional min. 50 measurements for each relevant test
scenario (see above). These additional samples can be
reduced or must be increased in dependence of the specific
additional check and its complexity to determine the
measurement uncertainty of the DUT.
Remarks:
All the additional tests must fulfil the error limits.
Traffic condition
based on a sample of 500 measurements:
~75 % different cars
length 3 m – 5 m or more
~5 % Motorcycles
~5 % Small trucks
~5 % Small trucks with trailer, caravan, etc.
~5 % Bus, Trucks and Lorries (long vehicles)
Remarks:
Recommendation for repetitive data
Route condition
Minimum two lanes in one or both direction
Remarks:
Checks on the road only on one lane with car by car is not sufficient
for the determination of the measurement uncertainty. A radar system
is sensitive of reflection from other vehicles or crash barriers etc.
Speed interval
speed limits of the speed system;
Remarks:
The speed system must works well inside the specific limits and
outside the limits it doesn’t work.
French Comment : setting a limit for braking and acceleration means to impose productivity for the
instrument and it’s not our goal. We think that breaking and acceleration of vehicles should be tested
but the only requirement is that it should not lead to error beyond the MPE.
Requirement to the
reference system:
The expanded uncertainty (see : JCGM 100:2008, GUM) of the
reference system shall be less than 1/3 of the MPE required for the speedmeter under test
Remarks:
Minimum requirements.
Supplement:
Today every prestigious manufactures is able to put speed
system on the market which fulfil the above requirements.
Modern traffic surveillance systems are today really
sophisticated. That’s good and gives a high confidential level for
polices, courts and driver.
The effect of these modern technologies is that the checking
instruments must follow this complex technology. Such test
instrumentations are expensive or must first be developed.
Close the eyes and believe what the manufactures specified is
no solution. Probably we must more work together. A serious
checked and then approved speed instrument is in the interest
of the manufacturer too.
Photo evidence :
In case of photo/video evidence, the vehicule which has been measured must be identified
without ambiguity on the photo/video
WF/2014/04/14
SG/2014/05/12