Special Print, Vehicles, Weigh-In-Motion - Traffic Data Systems GmbH

Weigh-In-
Motion
Remote WIM Systems
in Alpine Tunnels
Dr. E. Doupal, PhD,
Transport Research Center
R. Calderara,
Kistler Instrumente AG
Presented at
First International
Conference on Virtual and
Remote Weigh Stations
Orlando, FL, Feb. 2004
Special Print
920-331e-01.05

Remote WIM Systems in Alpine Tunnels
Abstract
This presentation provides brief information on multi-purpose applications of WIM stations for traffic data
collection and the following evaluations, operated in various remote control modes. An example from
Switzerland shows specific methods of online traffic data collection and evaluation.
The WIM data are used for a wide variety of applications depending on the requirements of the user or user
groups. The WIM stations equipped with a remote system can be used for various practical applications like
statistics, interval measuring and online traffic control, pre-selection of overloaded vehicles, estimation of the
current loading of road or bridge constructions and so on.
Keywords: weigh-in-motion, pavement loading, remote control, traffic data
1. Introduction
WIM (Weigh-In-Motion) systems are finding increasingly
widespread use as a valuable extension to conventional
traffic counters and classifiers.
They provide a whole spectrum of information on
traffic flow, with detailed data for each individual
vehicle, including:
• Dynamic weights of all axles (or if selected, even
left/ right half axles),
•Gross vehicle weights,
• Axle spacing,
• Distance between vehicles,
• Speed,
•Vehicle classification according to various schemes,
•Versatile statistic representations for all types of
traffic parameters.
Axle load measurement provides a better vehicle
classification rate than conventional traffic counters.
High precision WIM sensors as Kistler Lineas quartz
crystal sensors have proved their performance for
WIM systems maintaining good accuracy over years.
Traffic flow analyses including weight data are useful
beyond statistics for traffic planning, maintenance
prognostics and for automatically influencing the
rolling traffic.
The evaluated results can also be used as a basis for
determining dimensions in road and bridge construction
or for optimizing resurfacing work.
Both traffic volume and axle loading are continuously
increasing world wide and with the repetitive pounding
of roads, this often produces complex fatigue
failure modes. In the interest of minimising the
damage inflicted by overloaded vehicles passing over
critical road sections, particularly older bridges,
various highway authorities are pursuing a policy of
spot checks on vehicles suspected of exceeding
maximum load regulations.
The remote WIM site can be controlled and operated
from a central location using web-based or independent
communication systems.
The principle of a virtual WIM site is similar to that of
a remote WIM site, as it makes use of an existing or
new weigh-in-motion traffic data collection site. For
each monitored vehicle the traffic data are collected,
including vehicle classification and weight data are
transmitted together with a video picture, to an
enforcement operator (police). In case of an overloaded
vehicle, the operator will see the relevant
weight data highlighted and the picture of the vehicle
on the same screen. So the operator can pull the
vehicle over for further checking on a certified
weigh bridge. The pre-selection of vehicles allows
enforcement persons (police) to concentrate on the
potentially overloaded trucks, instead of detaining
non-offenders. A typical virtual WIM system complements
fixedly installed automatic high speed WIM
stations and remote data evaluation, traffic control
and enforcement scale systems.
Depending on user requirements, different data
formats and retrieving modes can be selected for the
entire WIM station or for individual traffic lanes. The
multi-user system is based on a password access
control system defined separately for every WIM
station. The following example from the Switzerland
WIM network shall illustrate this.
3

2. Alpine Transit Routes in Switzerland
Switzerland is a typical transit country with an additional
complication – Alpine mountains. The heavy
traffic between northern and southern EU countries
thus is channeled into three transit routes with long
tunnels and very high traffic volume. Main goals
are to protect these roads and to minimize road
damage from overloaded vehicles, as well as to
enhance traffic safety. In order to reduce the road
maintenance costs, the Swiss Federal Roads Authority
ASTRA (Amt fuer Strassen) had designed and ordered
the construction of a network system consisting
presently of 9 automatic weigh-in-motion (WIM)
stations; further ones are in the planning phase.
Automatic WIM System Sites
In operation
Projected
Planned WIM sites
Fig. 1: Swiss WIM stations network
4
Denges (A1)
Bözberg (A3)
Mattstetten (A1)
On the highway A2 (main North-South transit road
through the Alps region from Germany to Italy), a first
WIM system was installed in the Gotthard tunnel
(length >16 km, central Switzerland) in 1998 and a
novel four-lane remote traffic WIM system in and
outside of the Monte Ceneri tunnel (Canton Tessin,
southern Switzerland).
The traffic processor controls the traffic flow through
the high speed WIM:
Within the tunnel WIM and video systems are
installed for monitoring the overloaded or overheight
trucks. In addition, a warning signal can be passed on
to the highway police central station in Camorino
(near Bellinzona).
Oberbüren (A1)
Gotthardtunnel (A2)
Trübbach (A13)
Plazzastunnel,
Bonaduz (A13)
Courtesy ASTRA

Fig. 2: WIM system with quartz sensors installed in the Monte Ceneri
Tunnel
3. System Characteristics
• The WIM traffic data system consists of 32 quartz
crystal WIM sensors (Lineas Type 9195C from
Kistler) on 4 traffic lanes, and a data retriever
(Marksman 660 from Golden River), including data
transmission, software, and processor power supply
• induction loops triggering infrared detectors for the
height control system, in the South – North direction
• video cameras including installation for permanent
recording of traffic flow
• stationary signals, partly with folding mechanism for
adaptive signalisation
• local control facilities
STAMPANTE
STAMPANTE
North
MONITOR
VGA
MONITOR
VGA
Fig. 3: Remote WIM system overview – Tunnel control center and static weighing
Dakota
Dakota
Media
Converter
Media
Converter
HUB
Media
Converter
The ”Monte Ceneri Tunnel” consists of two tunnel
tubes with two (Northbound) and three (Southbound)
lanes per tube, all equipped with the traffic control
system.
Improvements in traffic flow can be achieved among
other means through harmonization of speeds on the
individual traffic lanes of the motorway by
• warning of overloaded vehicles, etc.
• warning of traffic jams
• traffic-adapted speed limit signalisation
• avoidance of traffic obstructions
The operational principle of the traffic control system
can be described as follows:
3.1 Data Acquisition
Traffic flow data and environmental data (speeds,
traffic volumes, precipitation, etc.) are acquired
locally by the electronics installed in roadside stations,
including
• the individual axle loads and the gross vehicle
weights of all vehicles
• the distances between vehicles
• traffic statistics per vehicle class, speed and time
intervals
Monte Ceneri Tunnel
Lighting zone
Lux = 104 min – Lux = 120 max
WIM system
M660
High control
HUB
Media
Converter
South
MONITOR
VGA
PC Switch
WIM
Power supply
GAEM
Dist. 230 Vac
5

3.2 Data Communication
The online data from the heavy traffic and the video
pictures are transferred to a sub center – the combined
police and road administration traffic control center in
Camorino, which is located near the control and
measuring facility some 3 km downstream in northbound
direction.
All ”vehicle by vehicle” measurement data are transferred
to the ASTRA center for the subsequent statistic
evaluation and data archiving.
3.3 Analysis and Calculation
The sub center analyses the results of the measurements
and the video pictures collected by the WIM
outstation, to enable an individual pre-selection of
overloaded or overheight vehicles. These data are
simultaneously transferred to the next police control
station downstream, equipped with an accurate low
speed weighing system for enforcement.
By identifying gross offenders in real time, they will be
automatically recorded and diverted to the weigh
bridge for mandatory static weighing and enforcement.
The data of these vehicles are recorded in a
separate database for police.
Thus with the remote WIM system this preselection
can be achieved without the unpopular slowing down
of the overall traffic flow, because only the preselected
vehicles will be stopped and weighed statically.
3.4 Individually Variable Traffic Data Format
The WIM station can be monitored and its data collected
hourly, daily or weekly according to operational
requirements. The remote mode can be set as readonly
(RO) for example for the police or local road
administration office use or as read-write (RW) access
for the system integrator. The potential for data corruption
through hacking is thus reduced. The system
has three levels of access:
6
Number of axle loads [%]
Fig. 5: Example of random axle loads
Random of axle loads divided in 20 load categories
Monte Ceneri tunnel – May 2003
Load category [t]
Fig. 4: Low speed WIM as a static scale for enforcement in Moleno
• Master user can setup all the system parameters
such as modem details, transfer protocols and location
of data folders. He only can set times and dates
for status and retrieval pool commands etc. All
parameters can be set and activated when required.
• Expert user will only see a reduced set of options
• Normal user has read-only access
The WIM site is individually configurable for modem
details, unit type, PC COMM port, baud rate, read
only and read/write passwords, filename and sensor
configurations.
The control or remote commands received from
the sub center Camorino or ASTRA center are
displayed with the variable programming of the
M660 WIM station.
The telemetry software and data retrieval system
maintains an outstation database containing the
phone number, site details and so on. Once a system
is set up, the system runs autonomously and has little
need for operator intervention.

Two weeks after the completion of the project components,
the calibration of the pre-selection high
speed WIM system (Monte Ceneri tunnel) and the
enforcement low speed WIM scales (Moleno) was
performed.
An example of a statistical use of WIM data is shown
on Fig. 5, which presents a set of random axle loads
divided in 20 load categories. This evaluation serves
as a basis for estimating the daily equivalent traffic
factor (DTV). The DTV factor is valuable for ASTRA
and the Canton authorities involved in road construction
and repair to reduce the maintenance costs.
The following graphs illustrate some results of accuracy
checks as performed periodically by ASTRA.
Fig. 6 shows data of dynamic gross weight measurements
with the Lineas WIM sensors compared to the
static weighing, 2 years after the Monte Ceneri installation.
40 heavy vehicles per lane randomly selected
from the traffic stream were diverted for static axle
weighing on a certified scale.
Monte Ceneri: Gross Vehicle Weights
of 40 random heavy vehicles
Fig. 6: Deviation of dynamic to static weights (% static GVW)
STD = 4,3 %
Fig. 7 shows the dynamic to static measurement deviations
for the same vehicle entity but per individual
axle loads. These results prove consistant accuracy of
Lineas quartz sensors in a heavily charged highway.
Individual Axle Loads of 1 st to 3 rd Axles
Deviations Dyn. vs. Static in %
STD Axle 1 4,9 %
STD Axle 2 5,7 %
STD Axle 3 5,6 %
Fig. 7: Deviation of dynamic to static axle loads for 40 random heavy
vehicles
4 Conclusion
Monitoring the effective vehicle weights not only
provides benefits for road design and planning, but
also enables more efficient enforcement of regulations.
The installation of remote and virtual WIM sites
enables permanent weight monitoring and enforcement
on the entire road network.
Accurate vehicle weight information is providing the
road contractors clear evidence of overloading if premature
structural damage occurs, thereby sustaining
the public road agency’s responsibility for efficient
weigh enforcement.
References
• Dagani M. and Doupal E. (2001) – Progetto WIM
Ticino, Canton Tessin, 160, Switzerland
• Calderara R., Helg Ch., Doupal E. (2000) Plane
sense, Toll Trans Aug/Sept 2000, U.K.
• Kavalec, K. (1999) Verkehrsverbunde in Deutschland,
2 nd Scientific Conference, University of Pardubice,
ISBN 80-7194-206-5, CZ
7

920-331e-01.05 Mat2000 ©2005, Kistler Instrumente AG
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