| Technology Profile
Left: Mobile low speed
weight control in Angola
Inset: The WL 400 strip
sensor has an 11m profile
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www.TrafficTechnologyToday.com 065
March/April 2020 Traffic Technology International
High benefits
at low speed
A WIM system is mostly
spoken of as a high speed
(HS) system, capable of
weighing vehicles’ tires and
axles on a normal roadway at
speeds up to 130 km/h. In
addition, these systems are quite
complex and are capable of
capturing and calculating
several traffic data elements,
such as vehicle classification,
dimensions, axle spacing and
plate number recognition. The
sensors in this case are
embedded into the pavement
surface and its installation is
quite costly, as well its
maintenance.
Popular choice
With the exception of a few
countries, direct enforcement is
still carried out with static scales
worldwide, be they portable
wheel load scales or weight
bridges. Although the
developments in WIM
technology have notably
increased, the skepticism about
the accuracy of WIM systems is
still very present – as there is so
far no technology able to
neutralize completely the
external factors that affect the
measurements.
| Need to know
Key attributes of the
WL 400 strip sensor
> Can be used as a lowspeed
WIM system up to
20km/h
> Capable of weighing up to
40 tons per axle
> Has an accuracy of +/-3%
at 10km/h
> The sensor weighs 2.3kg
The inexistence of an
accepted international standard
is another obstacle and the
dream of punishing every
single overloaded vehicle
automatically, without making
them stop, is still far from
reality. With this scenario, in
several cases the investment
in a HSWIM system is not
worthwhile.
Nevertheless, the low
speed WIM system can be an
intermediate solution. Despite
the limiting factor – the low
speed, normally up to 20 km/h –
the system can offer, depending
on the application, several
advantages.
In addition to the high
costs of the equipment itself,
its invasive installation and the
maintenance, a HSWIM system,
used for pre-selection in
conjunction of a static weighing
station requires a big area –
mainly for deceleration. Not
every country or highway has
such surface available. A low
speed (LS) WIM system needs
a much smaller area and the
operation can be carried out
at the same place where the preselected
vehicles can be further
measured with the static scales.
The portability of the LSWIM
system is another determining
factor. Once the vehicles will
sensor itself has an accuracy
of +/-3% at 10 km/h.
Due to its light weight – the
sensor weighs only 2.3 kg and
the whole system is less than
80 kg - the equipment is easy to
transport and can be used at any
time. Only an 11 mm profile and
1 meter in length, the sensor is
large enough for every vehicle
to drive over its active area.
The WL 400 has no display
and can be connected to a PC
with the software EC 200 for the
further processing, visualization
and printout of results.
Alternatively, it can be used
together with the processing
unit EC 120, which is very
compact, although it has an
integrated printer.
If the application is for
tolling or freight management
applications, the system can
also be placed in a recess in
the pavement. The installation
is much less invasive than a
HSWIM system and the sensor
can be removed at any time after
the operation.
Less costly than a HSWIM
system, portable, accurate and
easy to handle, the LSWIM
system WL 400 is a reliable and
compact weighing solution, that
fits both in the trunk of a car
and on any budget.
drive at a low speed on the
system, the use of levelling mats
is possible, making the system
totally mobile. Be the system
used itself for direct enforcement
or for screening, this mobility is
crucial for on the spot weight
enforcement, as the factor of
surprise is a great ally for
catching overload violators.
Value-added simplicity
To simplify pre-selection and
therefore add value to its range
of portable scales, Haenni
Instruments developed the
WL 400 strip sensor, that can
be used as a LSWIM system up
to 20 km/h and has a capacity
of 40 ton per axle.
“The sensor was launched
in 2018 as a major solution for
pre-selection”, says Marcia
Otter, business developer at
Haenni. “Nevertheless, the
market’s reaction was
unexpected. The biggest
demand for the WL 400 sensor
comes from the private industry,
which seems to be increasingly
concerned with controlling the
weight of its vehicles by
themselves. For the transport
sector the investment in such
a system is low compared with
the benefits of avoiding fines.”
Disregarding the influence
made by external factors, the
Haenni
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