Over the past two years, the concept of Virtual Weigh Stations (VWS) has attracted considerable interest. The concept is really an extension of the use of a more traditional Weigh In Motion (WIM) data collection site. Under the concept, a WIM data collection site is upgraded to include image capture capabilities. These allow the sites to be used for their traditional data collection purposes and as an enforcement screening tool. This dual application can make the systems quite attractive from a cost perspective.

The term ‘virtual’ comes from the fact that users can now perform most of the enforcement functions possible with a traditional weigh station or weigh check site but without the need for the physical building and infrastructure.

System features
A VWS system incorporates high-performance Weigh-In-Motion (WIM) equipment combined with video monitoring. Side vehicle image capture systems and License Plate Reading (LPR) cameras are integrated with the WIM systems. The side-fire images provide visual recognition of the type of vehicle that has passed. The LPR system can also include Optical Character Recognition (OCR) to automatically determine the licence plate number and place of registration. Additional technologies such as over-height and over-width detection can be added to the system as required.

Data collected from the various integrated systems is automatically analysed for verification of compliance with local size and weight regulations. When equipped with internet connectivity, the systems can provide advanced graphical user interfaces and can be accessed by an enforcement vehicle from anywhere wireless connections allow. The on-site system acts as a Web-enabled host, providing a mechanism via which enforcement offers can view the passage of traffic. The enforcement officer logs onto the site (which incorporates a firewall for security) and a display gives an easy-to-read graphical representation of the trucks passing as well as an indication as to the compliance of these vehicles in comparison to the local weights and dimensions regulations.

From a data collection point of view, WIM systems already have documented benefits. Agencies worldwide deploy hundreds of WIM systems that provide comprehensive data on vehicle volume, classification and weight information. This data is used to develop vehicle count, class and weight spectra that are used as fundamental input to modern mechanistic pavement designs. In addition, some agencies use comprehensive traffic data to monitor previous design assumptions, for early identification of an event or trend that will compromise the design. In this manner, corrective maintenance activities can be implemented before serious deterioration becomes a problem.

From an enforcement point of view, the system allows all commercial vehicle traffic to be monitored continuously for compliance with size, weight, safety and credential regulations. In one instance, knowing the trends and patterns of non-compliance can be identified, in order to better manage existing enforcement staff. The systems can also be used in real time to provide targeted enforcement while not impacting upon the traffic flow of compliant vehicles. This makes it possible to develop an enforcement strategy that optimises the effectiveness of resources.

New perspectives on monitoring
The use of VWS systems offer a cost-effective way to monitor commercial vehicle traffic in areas where it was not previously possible, either from a physical or cost perspective. These areas include urban or city locations, known evasion routes and remotely located sites with lower traffic volumes. There is an increasing awareness that overloading occurs in certain types of locations and is more prevalent in certain industries. Many VWS systems are being installed in urban settings, where truck overloading is as high as 25 per cent. This type of overloading significantly damages local road and bridge infrastructure, and exposes large numbers of motorists to potentially unsafe conditions.

To date, 20 or so VWS systems are operating in the United States and Canada, with a few others operating outside North America. The systems have contributed to successful demonstrations of capabilities, generating enough interest for further deployment plans. Several of these systems were installed under Federal and State demonstration programmes and as a result there will be analysis reports available as to the effectiveness of the equipment and concept.

Lessons learned
Some operating issues have been identified, however, and these can form the basis of ‘lessons learned’ for other agencies interested in the concept. A brief summary of these follows, with some commentary on good practice and what to avoid.

Good communications infrastructure is the key to the successful operation of VWS systems. While a traditional WIM data collection site stores a considerable amount of information on vehicles’ passage, this information is easily summarised and can be downloaded in an efficient, compressed form such that all data can be collected and manipulated. The video capture systems, on the other hand, generate significant volumes of data and handling that can be tricky, even with broadband internet connections to the systems. The handling of image capture data of any type over a traditional dial-up phone link is highly impractical. Provisions have to be made to handle relatively large amounts of information, as the system can store data amounting to several tens of gigabytes daily.

Another key area related to image capture data that has not been addressed sufficiently, is how to handle the large size and reporting of the image data. While typical WIM systems have the ability to generate reports on the WIM data, there is very little in the way of existing software that allows reporting specific to the number of occurrences of overloaded trucks on a vehicle-by-vehicle basis. Custom report software in several installations has streamlined this considerably but further work and attention needs to be given to this area of system operation, especially if an agency is interested in the wide-area deployment of a number of systems.

Wireless connectivity to the systems has improved significantly over the last year, as wireless companies have improved broadband capabilities and coverage. Even so, wireless broadband access can be sporadic and there are blackout areas that seem to coincide with locations of interest. While this technology holds a great deal of future promise, expectations that are too high in this regard may disappoint. In several of the existing urban installations, sufficient wireless broadband coverage has been available to allow demonstrations to be positive. However, as noted previously, there is a desire to install these systems in remotely located environments, and as a result, care must be given to the coverage available and the quality of the service.

There are several institutional issues that need to be addressed in most jurisdictions regarding the use of image capture and remote monitoring. The general public will be suspicious of any camera technology deployed, and rumours will abound as to the ‘real’ purpose of the systems. The local media can be a great ally in this regard but can also seriously jeopardise the programme if an incorrect feature is allowed to be deemed a reality. The suspicious nature of some people will very quickly create negative publicity if the agency has not developed a strong position politically on the use of the systems. The value of stakeholders meetings and prior buy-in to the concept by affected stakeholder groups should not be underestimated, nor should it be an afterthought. Successful programmes have gained the support of the local transportation department and the local police or enforcement staff as well as the local trucking community.

Any system that has the ability to undertake an enforcement activity will also generate interest from vandals. The camera systems and associated support hardware for these systems are high-value items. While the technology components are located in high traffic areas, there will be attempts to either steal the system components, or vandalise any part of the system that is deemed critical to the enforcement activities. Some system components can be mounted so as to be secure but care must be taken over equipment enclosures and other items that can be placed in high-risk areas.

Finally, these systems are most effective when combined with other successful practices within an enforcement agency. Effective enforcement in the area of commercial vehicles involves good visibility, fairness and a range of approaches. The most effective programmes use a combination of fixed equipment and comprehensive mobile crew capabilities. The use of any number of VWS systems by themselves will not make a programme a success if the enforcement programme is not balanced in the first place.

PUBLICATION: ITS International
DATED: 27th February 2006