Office of Operations Freight Management and Operations

3.0 Motivation for Virtual Weigh Station

3.1 Roadside Enforcement Challenges

The increasing numbers of commercial motor vehicles traveling on the nation’s roadways is the preeminent challenge faced by enforcement personnel.  At the same time, the enforcement workforce is not increasing to keep pace with the growing volumes; in many states, commercial vehicle enforcement personnel levels are less than their full complement.  This disparity between truck volumes and enforcement staffing – which is expected to widen – makes it difficult for State governments to ensure the safe, secure, and legal movement of commercial vehicles.

FHWA and the Federal Motor Carrier Safety Administration (FMCSA) report the following dramatic statistics concerning the commercial motor vehicle industry:

  • Commercial vehicles may move 100 percent more freight tonnage in 2035 compared to 2004, assuming moderate economic growth of three percent.  The tonnage could total over 30 billion tons in 2035.
  • To accommodate this increase in freight volume, commercial vehicle miles traveled (VMT) will need to increase.  It is estimated that truck VMT will increase 60 percent from 2005 to 2020, approaching 100 billion miles annually.
  • The large projected increases in truck VMT could result in a significant increase in the number of fatalities associated with large truck crashes.

In addition, this growth in truck VMT has the potential to increase the frequency between inspections of a commercial vehicle; increase congestion, delay, and the variability of transit times; increase freight transportation costs; degrade bridges and pavement more rapidly; and worsen air quality.

In this environment, states require new ways to work “smart.”  States are looking for systems that:

  • Automatically process large numbers of commercial vehicles while delaying only those that pose a safety risk or exceed weight regulations;
  • Expand the enforcement net to reach roadways and areas not adequately covered by existing enforcement operations while conserving enforcement resources;  and
  • Augment current enforcement processes to help mitigate the growth of unsafe commercial vehicle traffic.

3.2 Stakeholder Needs

Stakeholders include institutions, groups, companies, or individuals who:

  • Directly generate benefits realized by other stakeholders (e.g., data sharing, information exchange);
  • Have an interest in the short and long term success of the program in question;
  • Contribute to or are affected by some part of the program; or
  • Can influence the real or perceived success of the program.

Virtual weigh station stakeholders include State Departments of Transportation (DOTs), State and local enforcement agencies, other State agencies, Federal agencies, motor carriers, technology manufacturers and vendors, highway and commercial vehicle safety organizations, and the driving public. 

The Technology Implementation Group (TIG) of AASHTO selected “virtual weigh-in-motion” (i.e., virtual weigh station) as a focus technology.  According to the group, “the application of ‘virtual technologies’ demonstrates an innovative approach to solving size and weight enforcement issues that ranges beyond the WIM traditional role in data collection and vehicle classification.” (American Association of State Highway and Transportation Officials (AASHTO), Virtual Weigh-in-Motion:  A “WIM-win” for transportation agencies,, October 2006.) AASHTO is the leading source of technical information on design, construction, and maintenance of highways and other transportation facilities.  The TIG promotes technological advancements in transportation, sponsors technology transfer efforts, and encourages implementation.

The group identified the following list of virtual weigh station stakeholders: (American Association of State Highway and Transportation Officials (AASHTO), Virtual Weigh-in-Motion:  A “WIM-win” for transportation agencies,, February 2007.)

  • Driving public;
  • American Trucking Associations;
  • American Association of State Highway and Transportation Officials (AASHTO);
  • State Departments of Transportation;
  • State Departments of Revenue;
  • USDOT;
  • Federal Highway Administration (FHWA);
  • Federal Motor Carrier Safety Administration (FMCSA);
  • Commercial Vehicle Information Systems and Networks (CVISN) program partners;
  • State Highway Patrols/State Police and enforcement agencies; and
  • Motor carriers.

The operations of some of these stakeholders will be directly impacted by the deployment of virtual weigh stations.  These impacts will be clarified in the remaining sections of this document.

All stakeholders have the following high-level needs with respect to virtual weigh stations:

  • Reduce the numbers of highway fatalities and injuries;
  • Reduce the numbers of commercial vehicle crashes;
  • Reduce congestion and delay on highways;
  • Reduce diesel fuel consumption by commercial vehicles;
  • Decrease transportation costs for freight;
  • Preserve the highway infrastructure; and
  • Improve air quality.

Public agency stakeholders have the following additional needs:

  • Improve the efficiency and effectiveness of roadside enforcement operations;
  • Improve motor carrier compliance with Federal and State truck size and weight regulations;
  • Reduce infrastructure and enforcement costs; and
  • Provide data for traffic monitoring, pavement monitoring, and resource planning.

Motor carriers have the following specific needs:

  • Improve the reliability of scheduling highway-based freight deliveries;
  • Improve the efficiency of trips;
  • Increase productivity;
  • Level the playing field for safe and legal carriers;
  • Improve confidence levels in meeting transport contracting requirements;
  • Enhance company monitoring of driver performance and compliance; and
  • Enhance vehicle fleet tracking and goods tracking capabilities.

3.3 Assumptions and Constraints

Virtual weigh station deployment will be affected by existing or anticipated conditions that facilitate deployment (assumptions) and by limitations that potentially constrain deployment (constraints).

The following assumptions can be expected to facilitate virtual weigh station deployment:

  • Commercial vehicle traffic will increase according to current estimates (Section 3.1);
  • Enforcement resources available to conduct weight and safety inspections are limited and will become increasingly strained;
  • Funds available to support construction of traditional weigh or inspection stations are limited and will not appreciably increase;
  • Technologies exist to automatically identify commercial motor vehicles traveling at normal highway speeds;
  • Technologies exist to automatically weigh commercial motor vehicles traveling at normal highway speeds;
  • Potential violators according to weight, safety, credentials, and other factors can be identified and their data delivered to enforcement officials in real-time;
  • Costs of deploying a virtual weigh station are low compared to a fixed weigh or inspection station, regardless of the technology that is deployed at the virtual weigh station;
  • Many commercial vehicles avoid weighing by traveling on bypass routes or secondary roads, or during times when weigh stations are closed;
  • An even greater number of commercial vehicles are rarely subject to a safety inspection because they operate in areas without a roadside enforcement presence or the enforcement assets are limited;
  • Weight compliance is generally improved when enforcement operations are expanded;
  • Many State agencies are responsible for enforcing both weight and safety regulations; and
  • Safety inspections contribute to safer motor carrier operations.

The following constraints have the potential to inhibit virtual weigh station deployment:

  • Human resources are required to monitor real-time information from virtual weigh stations and intercept violators at the roadside for weighing and/or inspection, as long as the virtual weigh station is used as a screening tool.  In a study conducted by FHWA of challenges faced by states in deploying roadside enforcement technologies, participating states were quick to point out that during staffing shortages, systems that are not “permanently” staffed but require continuous human monitoring such as virtual weigh stations are of limited value. (Technology Deployment Challenges and Guidelines on the Use of Weigh-in-Motion in Roadside Enforcement, submitted by Cambridge Systematics to the Federal Highway Administration, April 2009, as part of the Truck Size and Weight Enforcement Technology Project, page 4.)
  • Although considerable strides have been made recently in automatically identifying vehicles traveling at highway speeds through optical character recognition (OCR) technologies, which are the most frequently deployed automatic vehicle identification (AVI) technologies deployed at virtual weigh stations, 100 percent accuracy in identifying all carriers (through their USDOT number) or vehicles (through their license plate) is not currently possible, and it is unclear whether 100 percent accuracy will be attainable with these technologies.  Most experts believe that accuracy will never approach 100 percent with these technologies because license plates and displayed USDOT numbers are not standardized and not optimized for automated reading.
  • Costs of deploying a virtual weigh station, despite being considerably lower than a traditional weigh station, can range from $300,000 to $1 million, based on a survey of State applications for Federal CVISN Deployment Grants, Fiscal Years 2006 - 2008.  Because costs depend on a large number of factors, such as whether a new WIM system is purchased and installed, the number of lanes, the number of other systems that are deployed (OCR, height detection, etc.), communications requirements, and integration needs, actual costs can be considerably less, or possibly greater, than these figures.  For states that are experiencing budget cuts and/or shortfalls, funding for additional costs such as virtual weigh stations may be difficult or impossible.

3.4 Description of Desired Virtual Weigh Station Operations and Processes

A virtual weigh station should support the following operations and processes in order to address the challenges described in Section 3.1 and meet the stakeholder needs described in Section 3.2:

  • Use technology to automatically identify carriers, drivers, and/or vehicles;
  • Distinguish potential weight violators from the real-time traffic stream based on automatic weight measurements that exceed established thresholds;
  • Distinguish high safety risk motor carriers, drivers, and vehicles from the real-time traffic stream based on an automatic screening algorithm that indicates the presence of safety risks, credentials violations, or other criteria established by the State;
  • Intercept potential weight violators for weighing on scales that produce enforceable weights;
  • Intercept high-risk carriers and vehicles for safety inspection and/or other close examination;
  • Allow safe and legal carriers/vehicles to travel unimpeded;
  • Conduct screening (weight, safety, credentials, and/or other criteria) on routes that do not generally capture traffic traveling past existing weigh stations, including bypass routes, secondary roads, highways in heavily populated urban areas, and remote highways;
  • Conduct screening operations to maximize available enforcement resources, e.g., coordinate operations with nearby weigh station operations;
  • Collect continuous data for planning purposes and make the data available electronically to stakeholders.  Planning purposes may include deployment of enforcement resources, as well as pavement and bridge monitoring, analysis of travel and weight trends, and development of emissions models;
  • Verify compliance with tax payment requirements (e.g., Heavy Vehicle Use Tax, International Fuel Tax Agreement) and vehicle registration requirements (e.g., International Registration Plan, intrastate vehicle registration); and
  • Verify, as applicable to the specific load movement, State-issued permitting procurement and compliance.

It is important to keep in mind that the concept of “virtual weigh stations” is to develop and deploy automated tools at the roadside capable of conducting measurements, verifications, and certifications traditionally conducted manually at fixed weigh stations.  Enforcement activities conducted at fixed weigh stations include:

  • Truck size and weight compliance measurements;
  • State-issued oversize/overweight permit availability and compliance;
  • Verification of registrations and payment of taxes and fees;
  • Driver credentialing and “hours-of-service” compliance; and
  • Carrier safety performance checks and vehicle and driver inspections. 

In addition, there is a growing recognition of the need to integrate services beneficial to the private sector at the roadside.  As compliance checks are conducted at highway speed, the “digital enforcement cloud” must be designed so as not to cause interference or interruption to company telecommunication and satellite-based fleet and goods tracking systems.  The high speed nature of “just-in-time” supply chain models requires advanced communication and identification systems; these capabilities have been in deployment in the private sector for several years now.  Interference with these systems by introducing non-compatible electronic data-heavy enforcement events at the roadside can be avoided through open communication and coordination with State trucking associations and large carriers.  Communication is vital to success.

Services available in an electronic format that support efficient movement of highway-based goods can be integrated into the roadside information exchange model as well.  Traffic operating conditions, construction zone awareness, road/ weather information services, and truck parking availability and reservation systems are examples of areas emerging as candidates for integration into roadside enforcement platforms.  At some point, State toll authorities offering e-tolling services may be integrated into the roadside data model to further enhance highway-based freight movement performance.  While these considerations and concepts each introduce added layers of complexity to an already complex enforcement model, the potential for integration and compatible system constructs will become more evident in the discussion and through the diagrams offered in the section that follows.

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