Highway Vehicle Overload Detection System & Vehicle Classification
November 2013





H-VODS-VC is an adaptive weigh station measuring and control system designed to count, classify and weigh vehicles as they drive through a weighbridge site.  It automatically detects and sorts overloaded, overheight and overlength vehicles and calculates the fines to be imposed on offenders.

High-speed pre-selection or sorting of vehicles is carried out at normal highway speeds using the VIPERWIM.The sorting system is location either in the main highway or in the approach lane to the weigh station.  If it is installed in the main highway, a diversion sign at the roadside is initiated whenever an overloaded vehicle is identified, directing that vehicle into the weighsite area a few hundred metres downstream.  In the alternative arrangement, with the high speed sorting system in the approach lane to the weighsite, a fixed message sign on the main highway diverts all heavy goods vehicles through the weigh station for high speed weighing and sorting.


Non-offending vehicles are returned to the main highway via a bypass lane with the minimum interruption to their journeys whilst overloaded vehicles are directed to the low speed WIM system in the enforcement weighing lane.

H-VODS-VC employs the TITAN Weigh-in-Motion Axle Weighbridge to provide a fully automatic vehicle classification and overload detection system.  H-VODS-VC controls traffic signals and a barrier response to the system’s interpretation of loading data, supervising and directing the movement of trucks through the weigh site.

The equipment is interfaced with a compatible standard PC which controls the timing operations and prints out penalty tickets in the official format and language of the country in which the system is operating.  It also provides a database for traffic statistics generated by H-VODS-VC as vehicles progress through the weigh site.

H-VODS-VC has a range of operator-selected program modes which enable control of the weigh station to be varied to suit changed in traffic volume throughout the day.  Graphics software provided with the system gives the operator a clear, comprehensive and live view of traffic movements, weighsite sensor functioning, overloading and other violations, and traffic signal and barrier operation.


Weigh Station Operation

The layout of a weigh station equipped with H-VODS-VC is shown schematically above.  It is depicted for countries where vehicles drive on the right.  For countries where driving is on the left, the layout is reversed, left-to-right.

The diagram shows a High Speed WIM (HSWIM) sorting system in the approach lane.  If an overloaded or overheight vehicle is detected, traffic signals automatically direct the vehicle into the enforcement lane.  If the vehicle is operating legally, the traffic signals switch the vehicle to the bypass lane where it returns to the main highway.  When an offending vehicle is sent to the enforcement lane, it moves over axle detectors, passes the overheight detectors and length measuring sensors and then over the Low Speed WIM TITAN axle weighbeam.  During this process, the vehicle is weighed and classified and checked for height and length.  These measurements are automatically compared with permissible limits programmed into H-VODS-VC for the class of vehicle identified and any infringements are flagged.

Truck movements in the weighsite area are under the control of the traffic signals on site.  These are switched by H-VODS-VC in response to the classifications and loadings identified by the system.  H-VODS-VC determines whether the truck is operating legally or infringing.  If the truck is within the legal loading limits and is not overheight, it will be returned to the highway without delay.  If H-VODS-VC detects an infringement, the truck is directed round to the Parking and Off-Loading Area for fining and payload readjustment.  The truck then returns to the enforcement lane for repeat weighing and reassessment.  Only when it conforms to the statutory legal limits is the truck allowed to return to the main highway.

Vehicle classifications vary between countries and H-VODS-VC can be programmed to cater for up to 20 different classes or categories.

Site Control and Monitoring using the PC

The weighbridge operator is able to view the weighing operations as trucks drive through the site, following movements displayed graphically on his VDU screen.  The upper part of the screen is a diagram of the enforcement lane, showing the traffic signals, the axle and vehicle detectors, the height and length detectors and the weighbeam.  Each is highlighted as the truck moves past, confirming satisfactory system performance to the operator or alerting him to any malfunction.  The status of the traffic signals and the traffic barrier are also shown.  As soon as the class of vehicle has been identified a truck outline appears in the lower part of the screen, annotated with axle and gross vehicle weight data, inter-axle spacing, vehicle length and vehicle class.  Violations of weight, speed and length are highlighted whilst individual overloaded axles are displayed in red on the truck outline.

This single comprehensive display gives the operator overall supervision of truck movements and weighing operations, alerting him immediately to loading infringements and any difficulties on site.

The PC operates from the specially created software package supplied with the system.  Not only does this enable complete weigh station control via the PC keyboard in conjunction with the graphics display, but it also logs data on a vehicle by vehicle basis; it produces weight and fines tickets in any previously agreed language and interacts with the High Speed WIM sorting system to show the weighing status of passing vehicles.

Optional supporting software packages are also available.  Traffdat enables on site analysis of data whilst Trafflink allows a remote headquarters base to interrogate and collect stored data via MODEM.

Site Control using the Operator Control Unit – OCU


Vehicle movements through the enforcement lane can be controlled using the desk top Operator Control Unit.  This unit allows the operator to vary the response of the system to match changes in vehicle interception requirements.  Five operational modes are available to the operator with two additional spare modes, programmable to suit site requirements.  Situations caused by traffic congestion on site can be dealt with by using the emergency button.  This sets all signals to RED, temporarily halting all vehicles on the site until the problem has been resolved.

Indicators on the front panel of the OCU represent the various sensors in the enforcement weighing lane.  Each is illuminated when a vehicle activates the associated sensor, demonstrating that the sensor is functioning correctly and also tracking the movement of the vehicle through the site.  If no fines tickets or data recording facilities are needed, the PC is not required and all weighsite operations can be managed entirely using the OCU.

TITAN Axle Weighbridge System

The dynamic weighbridge employed in the H-VODS-VC System is the TITAN Weigh-in-Motion Axle Weighbridge.  This uses a weighbeam measuring 300 x 75cm, handling axle loads up to 40,000kg.  Gross weights of up to N x 40,000 Kg can be recorded, where N is the number of axles on the vehicle.  On calibration, the reading indicated by the TITAN  axle weighbridge system is within 10 Kg of the true applied load.  Measuring resolution is 1 Kg in calibration mode and 10 Kg in weighing operations.  In service, the equipment records axle loads to an accuracy of ±10 Kg in static weighing mode and ±30 Kg in dynamic mode (depending on the road profile) for vehicles travelling at speeds up to 26 Km/h.

The performance of the weighing system meets the requirements of the UK Code of Practice for Dynamic Axle Weighers, issued by the UK Department of Transport and used for enforcement weighing standards.

The weighbeam, which operates at temperatures from -40˚C to +80°C, is supplied with a pit frame for installation in a weighpit in the enforcement traffic lane.

The read-out unit has two displays.  One is a weight display which reads in increments of 1 Kg and the other a status display showing operational modes.  These can be selected using the front panel keypad.  A tally-toll ticket printer is also available to give printed records of axle loads and gross vehicle weights.

Although the TITAN System is described in this application as part of the H-VODS-VC System, it can also be used independently as a dynamic axle weighbridge.  In either application the TITAN System has output ports to connect to a PC and to an external large flicker-digit weight display for viewing by vehicle drivers, as illustrated.

Static calibration of the TITAN axle weighbridge is carried out on the installed weighbeam using either of the two illustrated methods.  In one, precision dead weights are added to the weighbeam.  In the second, calibration loading frames are mounted on both ends of the weighbeam pit frame.  Each frame incorporates a precision load cell and gauge and loads are applied by means of a handpump and hydraulic cylinder.  The illustration shows the calibration system installed at one end of the weighbeam.  In either of the two calibration procedures, the reading on the TITAN digital read-out unit is corrected to indicate the same value as the applied load to the weighbeam.

Dynamic calibration of the TITAN system is performed using one or more trucks of known weight, making a number of passes over the weighbridge at a speed not exceeding 26km/h.

H-VODS-VC Hardware

The equipment required for a complete weigh station installation is selected depending on the functions required.  We can advise on weighstation layouts and equipment specifications to meet clients requirements.