Heavy vehicles can be weighed on static scales
(JPG picture 91 Kb), on low-speed weigh-in-motion scales at weighing
stations, which are driven over at a speed up to 15 km/h, or on
portable weighing pads, which are placed under the tyres of the
truck. While these weighing procedures are suitable for controlling
and fining overloaded vehicles, they are less appropriate for
traffic data collection. On static scales only a very small percentage
of freight vehicles is weighed. Low-speed weighing stations are rather
expensive to set-up and to maintain. They usually operate only few hours per
day and are therefore easily avoided. A great part of the heaviest,
most representative trucks is therefore not recorded. The same
problem is even more emphasized with the portable weighing pads.
On the other hand, high-speed WIM systems provide continuous unbiased weighing
of practically all vehicles passing the system. They are also
imperceptible which means that the drivers are not aware of the
weighing operation and do not try to avoid it.
Today there are approximately 1000 working WIM stations around
the world of which approximately 450 in the United States, 300 in
Europe (GIF picture 23 Kb, 1999) and 150 in Australia. They are also used in
South Africa, South Korea, Israel and in some other countries.
WIM systems are generally divided into:
permanent (sensors and the data acquisition systems collect data at
the same location),
semi-permanent (sensors are built into
pavement while the data collection system is moved from site to
portable (sensors and equipment are moved from
site to site).
According to the type of sensor, the weigh-in-motion systems are using:
Last updated on 17th
of July, 2006, by A.Znidaric