final report 

Concept of Operations for Virtual 

Weigh Station 

prepared for 

Federal Highway Administration 

prepared by 

Cambridge Systematics, Inc. 

100 Cambridge Park Drive, Suite 400 

Cambridge, Massachusetts 02140 

date 

June 2009 

Concept of Operations for Virtual Weigh Station 

Quality Assurance Statement 

The Federal Highway Administration (FHWA) provides high-quality information to serve 

government, industry, and the public in a manner that promotes public understanding. 

Standards and policies are used to ensure and maximize the quality, objectivity, utility, and 

integrity of its information. FHWA periodically reviews quality issues and adjusts its programs 

and processes to ensure continuous quality improvement. 

Concept of Operations for Virtual Weigh Station 

Table of Contents 

1.0 Introduction .........................................................................................................1-1

1.1 Statement of Problem .................................................................................1-1

1.2 Scope of This Document ............................................................................1-2

1.3 Organization of This Document ...............................................................1-2

2.0 Current Situation ................................................................................................2-1

2.1 Background..................................................................................................2-1

2.2 Overview of Fixed Roadside Enforcement Operations.........................2-1

2.3 Overview of Mobile Roadside Enforcement Operations ......................2-3

2.4 Overview of Existing Virtual Weigh Station Deployments..................2-4

3.0 Motivation for Virtual Weigh Station ............................................................3-1

3.1 Roadside Enforcement Challenges...........................................................3-1

3.2 Stakeholder Needs......................................................................................3-2

3.3 Assumptions and Constraints...................................................................3-4

3.4 Description of Desired Virtual Weigh Station Operations and 

Processes ......................................................................................................3-5

4.0 Concept of Operations .......................................................................................4-1

4.1 Virtual Weigh Station Goals......................................................................4-1

4.2 Functions of Virtual Weigh Stations ........................................................4-2

4.3 Key Concepts...............................................................................................4-3

4.4 Operational Scenarios ................................................................................4-4

Basic VWS Operational Scenario..............................................................4-8

Expanded VWS Operational Scenario ...................................................4-10

4.5 Architecture ...............................................................................................4-13

4.6 Common Steps ..........................................................................................4-17

4.7 Operational Policies..................................................................................4-19

4.8 Impacts .......................................................................................................4-19

5.0 Summary of Benefits and Costs.......................................................................5-1

5.1 Benefits .........................................................................................................5-1

5.2 Costs .............................................................................................................5-4

5.3 Available Funding Sources .......................................................................5-4

6.0 Conclusions..........................................................................................................6-1

i 
Table of Contents, continued 

ii 

6.1 Summary of Improvements ......................................................................6-1

6.2 Disadvantages and Limitations ................................................................6-1

6.3 Next Steps ....................................................................................................6-2

Appendix – Acronyms
Concept of Operations for Virtual Weigh Station 

List of Figures 

Figure 4.1 Basic Virtual Weigh Station Physical Layout........................................4-6

Figure 4.2 Expanded Virtual Weigh Station Physical Layout ...............................4-7

Figure 4.3 Basic Virtual Weigh Station Concept of Operations.............................4-9

Figure 4.4 Expanded Virtual Weigh Station Concept of Operations..................4-12

Figure 4.5 Basic Virtual Weigh Station Interfaces .................................................4-15

Figure 4.6 Expanded Virtual Weigh Station Interfaces ........................................4-16

iii 

Concept of Operations for Virtual Weigh Station 

1-1

1.0 Introduction 

1.1 STATEMENT OF PROBLEM

With commercial vehicle inspection resources stretched thin due to increasing 

traffic volumes, staffing cuts, and expansion of roles and activities, states are 

seeking new ways to monitor and enforce truck size and weight regulations. 

Limitations of fixed weigh station-based screening and enforcement activities 

(e.g., ability of overweight vehicles to use routes around the fixed sites to bypass 

enforcement resources) provide strong motivation for states to consider new 

approaches to roadside compliance verification and enforcement. These bypass 

routes are among many locations where violators are likely to travel that are 

monitored only by mobile enforcement officers whose presence may be sporadic 

and random. In many other locations, such as urban areas, a weigh station 

cannot be built due to environmental or cost reasons, but violators are likely to 

travel these roadways. A number of the “bad actors” purposely avoid detection. 

Many of these operators are habitual offenders. 

Resources for roadside safety inspections are especially scarce. According to the 

United States Department of Transportation (USDOT), approximately 177 

million truck weight inspections are conducted annually, versus only three 

million truck safety inspections.1 Of these three million inspections, 73 percent 

result in violations, whereas only 0.29 percent of weight inspections result in 

violations. Overall, truck safety compliance is problematic, but the low 

percentage of weight violations belies the numbers of overweight commercial 

vehicles that travel on roadways not monitored by traditional enforcement 

operations. 

In an effort to address these and other issues, states are deploying “virtual weigh 

stations.” Compared to a traditional weigh station, a virtual weigh station 

“mimics” the capabilities of the weigh station but do not require continuous 

human staffing and can be deployed more cheaply than fixed sites. No fewer 

than 14 jurisdictions received Federal Commercial Vehicle Information Systems 

and Networks (CVISN) Deployment Grants in Fiscal Years 2006 – 2008 to deploy 

“virtual weigh stations.” States also are using other Federal, or State, funds to 

deploy virtual weigh stations. An in-depth study conducted by the Federal 

Highway Administration (FHWA) in 2008 – 2009 documented the current State 

of the practice regarding “virtual weigh station” deployments and revealed a 

 

1 IntelliDriveSM website, sponsored by the United States Department of Transportation, 

Research and Innovative Technology Administration, June 18, 2009. 
Concept of Operations for Virtual Weigh Station 

1-2 

wide range of capabilities and little consensus on what constitutes a virtual 

weigh station.2

In fact, the term “virtual weigh station” is ubiquitous and often is used to 

describe any deployment of roadside technologies that occurs away from a fixed 

inspection site. If virtual weigh stations are to become an integral element of 

states’ commercial motor vehicle enforcement strategies – and indications are 

that they will – it is imperative that all stakeholders have a comparable 

understanding of the virtual weigh station concept. 

1.2 SCOPE OF THIS DOCUMENT

This document describes the concept of operations (ConOps) for the virtual 

weigh station (VWS). The ConOps describes the goals, functions, key concepts, 

architecture, operational scenarios, operational policies, and impacts of virtual 

weigh stations. A summary of benefits and costs follows the ConOps 

description. 

This ConOps will provide technical guidance to jurisdictions regarding their 

implementations of the virtual weigh station concept. The ConOps will be a tool 

that can be used to plan roadside programs, support states’ funding requests, 

obtain buy-in from public and private stakeholders, and communicate 

information among State, Federal, and private sector parties. 

Sections 4.0, 5.0, and 6.0 of this document describe the opportunities afforded by 

virtual weigh stations to address roadside compliance verification and 

enforcement challenges summarized above. 

1.3 ORGANIZATION OF THIS DOCUMENT

This document contains six sections. The sections are the following: 

1. Section 1.0, Introduction – Provides the context for developing a concept of 

operations for the virtual weigh station. 

2. Section 2.0, Current Situation – Reviews current roadside enforcement 

operations and existing virtual weigh station deployments. 

3. Section 3.0, Motivation for Virtual Weigh Station – Describes the challenges 

and needs underlying states’ virtual weigh station deployments and the 

operations that will address the challenges. 

 

2 State of the Practice of Roadside Technologies, submitted by Cambridge Systematics to the 

Federal Highway Administration, May 2009, as part of the Truck Size and Weight 

Enforcement Technology Project. 
Concept of Operations for Virtual Weigh Station 

1-3

4. Section 4.0, Concept of Operations – Presents the operational scenarios, 

information needs, and functionality associated with virtual weigh stations. 

5. Section 5.0, Summary of Benefits and Costs – Relates the expected benefits 

and costs of deploying virtual weigh stations. 

6. Section 6.0, Conclusions – Summarizes the enforcement improvements 

gained from virtual weigh stations, as well as limitations and next steps. 

An Appendix also is included, which presents a list of acronyms used in this 

document. 

Concept of Operations for Virtual Weigh Station 

2-1

2.0 Current Situation 

2.1 BACKGROUND

Unstaffed and remotely monitored roadside enforcement facilities – commonly 

called virtual weigh stations – are deployed to address some of the deficiencies in 

states’ traditional roadside enforcement programs. These facilities can expand 

the geographic scope and effectiveness of a State’s truck size and weight 

enforcement program by monitoring and screening commercial vehicles on 

routes that bypass fixed inspection stations and on secondary roadways, as well 

as in heavily populated urban or geographically remote locations where it may 

be difficult to deploy traditional enforcement operations. Data from virtual 

weigh station sites also can effectively target enforcement resources on roadways 

where overweight trucks are known or are suspected to operate. 

2.2 OVERVIEW OF FIXED ROADSIDE ENFORCEMENT 

OPERATIONS

Fixed weigh or inspection stations are the backbone of most states’ truck size and 

weight enforcement programs. In many states, the majority of weight 

inspections are conducted at weigh stations. These facilities intercept 

commercial vehicles entering or passing through a State on major highways. 

Currently, approximately 680 weigh stations are in operation in the United 

States.3 Customarily, signs on the highway direct commercial vehicles to pull 

into the stations where they are weighed by static scales to ensure that they are 

within Federal and State regulations. Both total gross weight and individual axle 

weights are measured and displayed to station operators. The primary purpose 

of these stations is to enforce truck weight regulations, in order to protect the 

infrastructure from excessive wear and tear caused by overweight trucks. 

It is efficient to screen trucks for safety, credentials, and logbook violations at the 

same time they are weighed. At the static scale, the truck is checked for obvious 

safety problems and for proper credentials, including the driver’s medical 

examination certificate and commercial driver license. In case of a problem, the 

truck is directed to an inspection area within the station for a closer examination. 

Some trucks may be selected for closer inspection in a random manner or 

because of the officer’s experience with the carrier, in addition to visual clues 

seen by the officer. In many cases, officers will use identifying information on 

 

3 2009 Rand McNally Motor Carriers’ Road Atlas, 2009. Massachusetts and New York are 

the only states that indicate there are no permanent weigh stations used in the State. 
Concept of Operations for Virtual Weigh Station 

the truck to query safety and credentialing data repositories (e.g., State 

Commercial Vehicle Information Exchange Window [CVIEW], national Safety 

and Fitness Electronic Records [SAFER]) to determine if the carrier has a history 

of poor safety performance and/or to verify the current status of motor carrier 

and commercial vehicle credentials. For example, the USDOT or license plate 

number can be used in a manual or automated check of a carrier or vehicle 

database (e.g., CVIEW), yielding an Inspection Selection System (ISS) inspection 

value and recommendation or registration or tax payment status. The ISS is a 

decision-aid for commercial vehicle/driver inspections, which guides inspectors 

in selecting vehicles for inspection; the ISS value or score is based on a motor 

carrier’s safety performance data. 

The effectiveness of fixed weigh stations is affected by: 

 Limited physical and processing capacity that can be regularly overwhelmed, 

resulting in commercial vehicles backing up onto the highway and requiring 

closure of the station so that public safety is not impacted by the lengthening 

queue; 

 Limited geographic coverage (i.e., each facility supports enforcement 

monitoring over a limited portion of a roadway); 

 Limited hours of operation, which largely are driven by availability of 

staffing and financial resources; 

 Inability to deploy fixed sites in some areas (e.g., remote, urban) that are in 

need of commercial vehicle enforcement; and 

 Expenses associated with the acquisition, development, operation, and 

maintenance of the sites. 

These stations also can cause motor carrier delays that range from a few minutes 

to extended queue times for trucks waiting to be weighed. Unnecessary delays 

and prolonged transit times adversely impact a carrier’s ability to bid 

competitively on delivery contracts. 

In order to address some of these limitations, the vast majority of states currently 

support electronic screening at many of their fixed facilities. Electronic screening 

is the automated screening of vehicles that pass a roadside check station, 

determining whether further inspection or verification of credentials is required, 

and taking appropriate actions. Electronic screening requires a change in the 

traditional concept of pulling in every truck for weighing and inspection. In 

electronic screening, commercial vehicle traffic is sorted to distinguish between 

known or likely safe and legal vehicles and potential violators before they stop at 

an inspection facility. The intent of electronic screening is to allow safe and legal 

trucks to pass the station while enforcement resources are focused on high-risk 

carriers and vehicles. Mainline weigh-in-motion (WIM) is frequently used as 

part of an electronic screening system, providing real-time weight verification 

concurrent with automated safety and credentials verification for bypass 

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Concept of Operations for Virtual Weigh Station 

eligibility. Vehicles cleared for bypass are not generally directed to pull into the 

weigh station. 

States with electronic screening have reported a reduction of 15 to 20 percent in 

the volume of truck traffic passing through weigh stations that are instrumented 

with the capability. The reduction is directly related to the level of participation 

in electronic screening by motor carriers. Clearly, the greater the participation of 

carriers in electronic screening programs, the less likely it is for queuing to close 

weigh stations and legal trucks to need to pull into weigh stations. The benefit to 

the carrier is the ability to travel past the weigh station without stopping. For the 

State, electronic screening allows enforcement resources to be focused on highrisk carriers and vehicles. 

Electronic screening cannot address all of the limitations associated with fixed 

weigh stations. Even with electronic screening, noncompliant vehicles can 

attempt to bypass the enforcement station by using a route that goes around the 

site. Weigh stations also may have restricted and often predictable hours of 

operations. As a result, overweight trucks may travel when weigh stations are 

closed, at night, and on weekends. Electronic screening also does not address the 

costs and the physical space that are required to deploy a weigh station. 

Because weigh stations often are bypassed or otherwise avoided by overweight 

trucks, significant effort is expended on compliant carriers, providing incentive 

for states to implement tools and methods to better target high-risk carriers and 

vehicles. 

2.3 OVERVIEW OF MOBILE ROADSIDE ENFORCEMENT 

OPERATIONS

Mobile enforcement consists of enforcement activities that do not take place at 

fixed weigh or inspection stations. States’ mobile enforcement programs usually 

encompass temporary roadside locations (e.g., rest areas, modified shoulders, 

abandoned weigh stations), roving patrols, or both. These activities typically are 

conducted on routes without fixed weigh stations, on secondary roadways, and 

in remote areas. Mobile enforcement allows states to expand their enforcement 

efforts away from the Interstate and major highways and onto secondary and 

smaller roads that are known bypass routes around fixed stations. 

During mobile enforcement details, commercial vehicles are stopped and 

weighed on portable scales. States also may opt to conduct a safety inspection, 

and/or credentials verification based on random selection, visual clues, or 

experience (or inexperience) with a particular carrier. At the roadside, common 

visual clues are an appearance of being overweight and observed safety 

problems. Enforcement officers may stop a vehicle after an automated (using a 

laptop computer capable of accessing a database or the Internet) or radio check 

of the driver’s license number, vehicle license plate number and/or vehicle 

identification number (VIN), or USDOT number. If a temporary roadside 

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Concept of Operations for Virtual Weigh Station 

2-4 

location is being used, officers may attempt to stop all approaching trucks, 

depending on traffic conditions. Note that in some states, probable cause is 

required to stop a vehicle. 

Compared to weigh stations, mobile weight enforcement operations process a 

smaller volume of trucks, although the percentage of violators is arguably 

higher. Similarly, most safety inspections are conducted at weigh stations 

(where it is a safe place to put a truck out-of-service), but indications are that the 

number of inspections is growing at mobile locations. 

Incorporating WIM systems into mobile operations provides the State with the 

potential to weigh a greater number of trucks. WIM equipment can be installed 

in the pavement or it can be portable. Mobile teams can set up in vans and move 

equipment around as needed, or they can set up in the area of a permanently 

installed WIM system. Real-time WIM data can be viewed by roadside 

enforcement personnel on laptop computers, who visually identify the potential 

violators. Automatic identification of violators (relieving the need for manual 

visual recognition of suspect vehicles) is possible with the incorporation of 

advanced roadside-based technologies (e.g., license plate readers). 

The importance of mobile operations in states’ overall commercial vehicle 

enforcement programs is increasing as many states “deemphasize” weigh 

stations that are expensive to build and maintain. However, the effectiveness of 

mobile units is limited by the number of roadside personnel that can be deployed 

by a State. Furthermore, with dwindling resources, it is difficult for states to 

expand mobile enforcement coverage. Under such conditions, just as weigh 

stations equipped with electronic screening attempt to focus on high-risk 

operators, states are pursuing new ways to effectively target their resources on 

high-risk carriers, drivers, and vehicles during mobile operations. 

2.4 OVERVIEW OF EXISTING VIRTUAL WEIGH 

STATION DEPLOYMENTS

At least 10 states across the United States have deployed a virtual weigh station 

to date. States deploy virtual weigh stations in order to enforce legal truck 

weights and to protect the State’s investment in the infrastructure. These states’ 

deployments vary in terms of their operational focus (e.g., screening commercial 

vehicles, supporting planning for the deployment of enforcement resources) and 

technologies used (e.g., WIM, license plate reader, USDOT number reader). 

These deployments are documented in a FHWA study of the state of the practice 

regarding virtual weigh station deployments.4 What all of these deployments 

 

4 State of the Practice of Roadside Technologies, submitted by Cambridge Systematics to the 

Federal Highway Administration, May 2009, as part of the Truck Size and Weight 

Enforcement Technology Project. 
Concept of Operations for Virtual Weigh Station 

have in common is a WIM system that supports real-time screening activities at 

locations that are unstaffed and away from weigh stations. 

In Fiscal Years 2006 – 2008 a total of 14 jurisdictions received Federal CVISN 

Deployment Grants for virtual weigh station deployments (a few of these states 

have completed their deployments and are counted in the 10 states mentioned 

above). These states’ virtual weigh station deployments may include – in 

addition to WIM scales or sensors – cameras, optical character recognition (OCR) 

technology, system electronics, screening software, system integration, and/or 

expanded communication networks to support the timely and secure 

transmission of data to users, as well as integration of safety data/screening 

algorithms into roadside operations. 

Some states have deployed VWS technology as part of a mobile screening system 

in which an officer at the roadside with a laptop computer receives individual 

axle weights and gross vehicle weights that are wirelessly transmitted from the 

WIM device on the mainline that is being monitored to the mobile officer’s 

laptop. The officer physically monitors the real-time WIM data on the laptop 

and visually identifies the trucks that are overweight according to the data 

received. The potentially overweight trucks are then intercepted for inspection 

after traveling past the WIM site. Having quantifiable performance 

measurements avoids stopping vehicles that are legal according to weight 

thresholds established by the State. 

A few states have added a roadside digital camera system to the mobile 

screening system to facilitate the identification of suspect commercial vehicles. 

In these operations, an enforcement officer views the real-time WIM data linked 

with a vehicle photo on a laptop computer in the patrol vehicle located 

downstream of the WIM site. Multiple photos also may be displayed in 

thumbnail form so the officer can easily select from different views of the vehicle 

of interest. Suspect vehicles are identified on the laptop, facilitated by visual 

and/or sound alerts. In one scenario, the officer monitors the data and images 

and intercepts the violators. The same data and images may be viewed by 

enforcement personnel in a fixed facility. In a different scenario that is deployed 

by states, instead of an officer located downstream performing monitoring and 

weighing functions, personnel viewing the WIM data and images at a nearby 

weigh station will dispatch nearby enforcement units to intercept and weigh 

suspect vehicles identified on the monitor. 

As part of the “2006 Commercial Motor Vehicle Size and Weight Enforcement in 

Europe” scan sponsored by FHWA in cooperation with the American 

Association of State Highway and Transportation Officials (AASHTO) and the 

National Cooperative Highway Research Program (NCHRP), the scan team 

observed the use of high-speed weigh-in-motion (HSWIM) and vehicle image 

capture using digital cameras as a common enforcement site layout. The COST 

(Cooperation in Science and Technology) 323 truck weight enforcement protocol 

used throughout Europe since the late 1990s, entitled WIM/VID, calls for 

WIM/visual identification capability for screening at the roadside. The 

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Concept of Operations for Virtual Weigh Station 

2-6 

simultaneously captured picture of the motor vehicle and its associated axle and 

gross vehicle weight values are used immediately by enforcement officials who 

are preselecting certain trucks for more extensive inspections, or the data are 

processed and stored for further analysis and use at a later time. 

This system configuration (i.e., “bundled” WIM and digital imaging functions) is 

not currently deployed in the United States; however, it is now readily available 

in North America. “Off-the-shelf” virtual weigh station technology packages 

including digital image capture coupled with HSWIM telemetry are offered by 

several vendors at this time. 

Several states have deployed a license plate reader (LPR) or USDOT number 

reader to provide automatic vehicle identification (AVI). These technologies use 

a digital camera or cameras augmented with specialized OCR software to isolate 

and identify specific characters and numbers making up a license plate number 

and/or USDOT number. AVI relieves the need for any kind of manual visual 

recognition, whether it is based on direct observation of the vehicle itself or 

examining a photo of the vehicle. 

The concepts of operations for basic and expanded virtual weigh stations are 

provided in Section 4.0. 
Concept of Operations for Virtual Weigh Station 

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. 

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Concept of Operations for Virtual Weigh Station 

3-2 

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.”5 

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:6

 Driving public; 

 American Trucking Associations; 

 American Association of State Highway and Transportation Officials 

(AASHTO); 

 State Departments of Transportation; 

 State Departments of Revenue; 

 

5 American Association of State Highway and Transportation Officials (AASHTO), 

Virtual Weigh-in-Motion: A “WIM-win” for transportation agencies,

http://www.transportation.org/sites/aashtotig/docs/VWIM%20Brochure%20Final%2

010-27-06.pdf, October 2006. 

6 American Association of State Highway and Transportation Officials (AASHTO), 

Virtual Weigh-in-Motion: A “WIM-win” for transportation agencies,

http://www.transportation.org/sites/aashtotig/docs/021907%20Short%20Version.pdf

, February 2007. 
Concept of Operations for Virtual Weigh Station 

 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 

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Concept of Operations for Virtual Weigh Station 

 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 realtime; 

 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: 

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Concept of Operations for Virtual Weigh Station 

3-5

 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.7

 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; 

 

7 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. 
Concept of Operations for Virtual Weigh Station 

 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. 

3-6 
Concept of Operations for Virtual Weigh Station 

3-7

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 etolling 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. 

Concept of Operations for Virtual Weigh Station 

4-1

4.0 Concept of Operations 

A virtual weigh station (VWS) is an enforcement facility that does not require 

continuous staffing and is monitored from another location.8 The virtual weigh 

station concept is very flexible. While there is a minimum set of 

functionality/technology that must be deployed in association with a VWS, 

states can customize their VWS deployments to meet their specific functional

needs (e.g., focus exclusively on truck size and weight issues, expand focus to 

include safety and credentialing regulations), operational environment (e.g., 

typical weather conditions, physical space, terrain), and communication 

infrastructure (e.g., presence of communication infrastructure at site, presence of 

power at site). This section documents the basic VWS concept, as well as 

additional functionality that can be associated with an expanded VWS. 

4.1 VIRTUAL WEIGH STATION GOALS

Virtual weigh stations are employed to meet a wide range of operational 

objectives. States typically deploy virtual weigh stations in order to: 

 Increase compliance with Federal and State size and weight standards 

through augmented enforcement operations (e.g., screening commercial 

vehicles; persistent enforcement operations on known bypass routes around 

fixed facilities; persistent enforcement operations on routes that are not 

regularly patrolled by mobile enforcement assets due to 

remoteness/geography/topography); 

 Improve commercial vehicle safety through targeted enforcement at 

commercial vehicles that are known to be overweight, are improperly 

credentialed, or are operated by high-risk motor carriers; 

 Improve the efficiency and effectiveness of roadside enforcement assets; 

 Improve resource allocation and staffing decisions through the use of 

information; and 

 Reduce costs associated with the expansion of commercial vehicle size and 

weight/safety enforcement programs through the use of technology. 

As states consider the next generation of roadside technologies, VWS sites also 

may be designed to serve as conduits for two-way communication between the 

 

8 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 12. 
Concept of Operations for Virtual Weigh Station 

roadside and a vehicle in motion and therefore may support a broader range of 

safety, security, mobility, and systems management objectives. 

4.2 FUNCTIONS OF VIRTUAL WEIGH STATIONS

As noted above, virtual weigh stations can be designed and implemented to 

support a wide variety of roadside enforcement functions. At a minimum, a 

VWS must support the following functionality: 

 Real-time weighing of a commercial vehicle—Determine a commercial 

vehicle’s approximate axle weights as the vehicle moves across sensors, and 

calculate the gross vehicle weight and classification based on the number of 

axles, as well as axle weights and spacings; 

 Real-time identification of a commercial vehicle—Identify accurately all 

commercial vehicles that pass the site; 

 Integration of real-time data for screening decisions—Integrate commercial 

vehicle identification and weight data in real-time/near real-time, in order to 

support manual (i.e., decisions made by roadside enforcement personnel) or 

automated (i.e., decisions calculated by the system and then forwarded to a 

human) targeting of specific commercial vehicles for further enforcement 

action; and 

 Communication of data to enforcement personnel in real-time—

Communicate VWS data (e.g., vehicle photo, weight data) to authorized 

users (e.g., mobile enforcement personnel stationed downstream from the 

VWS, enforcement personnel stationed at a fixed inspection site that could be 

dispatched to intercept an overweight vehicle) in a timely and secure 

manner. 

States also use their current VWS deployments to support the following 

expanded functionality: 

 Real-time identification of the motor carrier responsible for the operations 

of a commercial vehicle—Identify the motor carrier that is responsible for 

the safe operation of the vehicle; 

 Implementation of an expanded screening algorithm—Integrate additional 

criteria (e.g., motor carrier history of safety performance, motor carrier 

history of compliance with size and weight standards, current commercial 

vehicle credential status, current motor carrier credential/operating authority 

status, driver’s license status) into the screening decision; 

 Real-time verification of vehicle dimensions—Integrate additional sensors 

(e.g., gantry-mounted laser overheight detectors) to determine if a 

commercial vehicle exceeds legal height, width, and length regulations and 

therefore would require an oversize/overweight permit; and 

4-2 
Concept of Operations for Virtual Weigh Station 

 Availability of data to support resource planning—Provide commercial 

vehicle average daily trip data (e.g., volume, weight, vehicle classification) in 

order to support the scheduling of mobile enforcement activities, as well as to 

identify locations in need of fixed enforcement facilities. 

During recent stakeholder discussions about the future uses of roadside 

technologies, stakeholders also identified a series of additional functionality that 

could be supported by a VWS. This additional functionality includes: 

 Real-time identification of the commercial driver operating a commercial 

vehicle and inclusion of driver information in the screening decision—

Identify the individual driving a commercial vehicle and determine if that 

individual can legally operate the vehicle at that time (i.e., commercial 

driver’s license is not revoked or suspended); 

 Direct enforcement—Write a citation or take other enforcement action (e.g., 

prevent a commercial vehicle from being started) based on data from a VWS; 

 Communication of real-time operational data to system managers—Serve 

as a conduit for onboard vehicle data (e.g., speed, windshield wipers on/off, 

air temperature) to be sent to traffic management centers in support of 

traffic/congestion monitoring and development of travel advisories; 

 Communication of real-time traveler information to commercial drivers—

Serve as the means by which real-time traffic (e.g., incident warning, 

congestion, weather advisories) and truck parking (e.g., location, availability) 

information could be delivered to commercial vehicle drivers operating 

within a specific geographic area/corridor; and 

 Communication of commercial vehicle location data to authorized users—

Accurately capture vehicle location data (i.e., date and time that it passed a 

VWS) in order to support private sector (i.e., asset tracking, estimated time of 

arrival [ETA] updates to vehicle’s motor carrier/shipper/receiver) and 

public sector (i.e., tracking of hazardous material by Department of 

Homeland Security, tracking of in-bond agricultural shipments by the United 

States Department of Agriculture) applications. 

4.3 KEY CONCEPTS

The basic virtual weigh station functionality is based on the following concepts: 

 Use roadside technology to augment human enforcement resources; 

 Deploy scarce enforcement resources as effectively and efficiently as possible; 

 Accurately identify all commercial vehicles in real-time; 

 Determine a commercial vehicle’s weight to a degree of accuracy that is 

sufficient for its functional purpose (e.g., 10 - 15 percent error tolerance for 

system monitoring while building knowledge on system-level loadings; 3 - 5 

4-3
Concept of Operations for Virtual Weigh Station 

percent error tolerance for mainline WIM systems for screening; 1 - 2 percent 

error tolerance for ramp WIM for sorting at weigh stations); 

 Deliver the vehicle identification and weight data to enforcement personnel 

in real-time; 

 Leverage other safety and credentialing data in screening criteria; 

 Focus enforcement on commercial vehicles that pose the highest risk; and 

 Deploy VWS technology in an open and expandable way so that future 

technologies (e.g., enhanced vehicle identification systems, driver 

identification systems, Smart Roadside, IntelliDrive/Commercial Vehicle 

Infrastructure Integration) can be integrated easily and cost effectively. 

4.4 OPERATIONAL SCENARIOS

Varying technology is required to support the different types of VWS 

functionality (documented in Section 4.2). The minimum VWS functionality 

requires deployment of: 

 WIM scales or sensors, which weigh the commercial vehicle; 

 Camera (digital imaging) system, which captures real-time images of a 

commercial vehicle crossing the WIM system to support its immediate 

identification by enforcement personnel; 

 Screening software, which integrates the data from the WIM and imaging 

systems; and 

 Communication infrastructure, which makes the VWS data (e.g., vehicle 

photo, weight data) available to authorized users (e.g., mobile enforcement 

personnel stationed downstream from the VWS, enforcement personnel 

stationed at a fixed inspection site that could be dispatched to intercept an 

overweight vehicle) in a timely and secure manner. The VWS allows for the 

use of a variety of communication technologies. Depending on what is 

available at the site, authorized personnel may use a wireless connection 

(e.g., cellular, satellite) or a wired connection (e.g., fiber optics, T-1 line) to a 

secure Internet site to access the information. 

The following types of technology also may be deployed in order to support 

additional VWS functionality: 

 License plate reader (LPR) and/or USDOT number reader system, which 

takes an image of the vehicle’s license plate or side of the commercial vehicle 

and uses OCR software to generate an electronic value of the vehicle’s license 

plate or USDOT number, respectively; 

 Commercial Vehicle Information Exchange Window (CVIEW) or an 

equivalent, which provides real-time access to motor carrier safety (e.g., outof-service [OOS] orders, safety algorithm scores) and credentials (e.g., 

4-4 
Concept of Operations for Virtual Weigh Station 

4-5

operating authority, Unified Carrier Registration [UCR], International Fuel 

Tax Agreement [IFTA]) data, as well as commercial vehicle safety (e.g., past 

inspection reports) and credentials (e.g., International Registration Plan [IRP], 

oversize/overweight [OS/OW] permits, intrastate vehicle registration) data. 

This repository also could contain commercial driver’s license data for use in 

the screening process;

 State-issued permit compliance, which accesses on-board information in 

order to verify a permit has been obtained and is in valid operation when 

oversize or overweight elements are detected. Verification that the vehicle is 

operating on an “approved route” and at a legal time and within the limits 

provided for on the State-issued permit can be conducted at highway speed 

with proper information added to a transponder or radio frequency 

identification-based device, or through the real-time accessing of permit data 

stored in back-office safety and credentialing systems (i.e., CVIEW, OS/OW 

permitting system);

 Repository of past weight performance, which provides real-time access to a 

motor carrier’s and/or commercial vehicle’s previous compliance record 

with Federal and/or State truck size and weight limits;

 Driver identification system, which provides an electronic means to 

accurately identify the operator of a commercial vehicle while the vehicle is 

in motion;

 Augmented WIM scales, which enhances the accuracy in the weighing of the 

commercial vehicle, in order to support more reliable screening and ramp 

sorting enforcement operations; and

 Two-way communication, which provides the ability to share data from the 

commercial vehicle (e.g., speed, windshield wiper on/off, temperature) to the 

roadside, as well as from the roadside to the commercial vehicle (e.g., traveler 

information, truck parking information).

Figure 4.1 illustrates a typical layout of a basic VWS. Figure 4.2 illustrates the 

potential layout of a more robust VWS. To illustrate how operations of the basic 

VWS and a more robust VWS may differ, an operational scenario for each is 

detailed following the layout illustrations. 
Concept of Operations for Virtual Weigh Station 

4-6 

Mainline

Bypass Route

1

2

3

2A 

2B 

2C 

2D 

Figure 4.1 Basic Virtual Weigh Station Physical Layout 

Legend

1 . Fixed weigh 

highway 2. Virtual weigh bypass route  2A. WIM sc 2B. Camer 2C. Screen 2D. Comm3. Mobile enfordownstream fro
Concept of Operatio

Legend

1. Fixed wehighway 2. Virtual wbypass rou 2A. W 2B. D 2C. A 2D. Co 2E. Sc3. Mobile edownstream 4. State/UrManageme5. Back-offiData Cente6. Motor cacenter 

Traffic Management 

Center

Mainline

Bypass Route

1 

2B

3 

4 

Motor Carrier

2A

2C

2E

2D

State Data Center

5 

FMCSA Data

Center

Figure 4.2 Expanded Virtual Weigh Station Physical Layout 

6 
Concept of Operations for Virtual Weigh Station 

Basic VWS Operational Scenario 

As illustrated in Figure 4.3, the following five steps summarize the typical 

operations of VWS: 

1. As a commercial vehicle approaches the virtual weigh station, it is weighed 

while in motion on the WIM scales. 

2. A picture of the commercial vehicle is taken for identification purposes. 

3. Screening software integrates data from the WIM and camera system. 

4. Mobile enforcement officer positioned downstream from the VWS accesses the 

VWS data (e.g., photo of commercial vehicle, WIM data) and makes a screening 

decision. Enforcement personnel at the fixed site access the VWS data (e.g., 

photo of commercial vehicle, WIM data) and make a screening decision. 

5. Overweight commercial vehicle is intercepted for weighing/inspection. 

4-8 
Concept of Operations for Virtual Weigh Station 

Figure 4.3 Basic Virtual Weigh Station Concept of Operations 

Mainline

Bypass Route

4

1 

4

3 

4

5 

2 

4-9
Concept of Operations for Virtual Weigh Station 

Expanded VWS Operational Scenario 

As illustrated in Figure 4.4, the following 13 steps summarize the potential 

operations of a VWS in the future: 

1. As a commercial vehicle approaches the virtual weigh station, it is weighed on 

the WIM scales and measured by dimensional sensors. 

2. AVI system automatically identifies the specific vehicle. 

3. License plate/USDOT number reader and associated optical character 

recognition (OCR) software identify the motor carrier that is responsible for 

operating the commercial vehicle. 

4. Screening system uses vehicle identifier and motor carrier identifier to query 

back-office safety, credentials, and weight performance data. (NOTE: These data 

may be stored in a single repository, such as a State’s Commercial Vehicle 

Information Exchange Window [CVIEW], or in separate repositories.) 

5. Screening system integrates weight data with safety, credentials, and weight 

data in order to determine whether a commercial vehicle should be targeted for 

additional enforcement actions. 

6. Mobile enforcement officer positioned downstream from the VWS and/or 

enforcement personnel stationed at a fixed site access the VWS system (e.g., 

photo of commercial vehicle, vehicle identifier(s), WIM data, screening decision). 

7. A commercial vehicle/motor carrier that is overweight or noncompliant with 

safety (e.g., out-of-service order) or credential (e.g., IRP, IFTA, UCR, OS/OW) is 

intercepted for weighing/inspection. If monitoring is conducted at the fixed site, 

an officer is dispatched to locate and pull the vehicle over for 

weighing/inspection, or direct the vehicle to the weigh station for 

weighing/inspection. 

8. If human resources are unable to intercept the vehicle, a warning letter or a 

citation could be generated by a back-office process and forwarded to the motor 

carrier identified by the USDOT reader. The concept of issuing warning letters 

to motor carriers that are routinely noncompliant is consistent with FMCSA’s 

new operational model (Comprehensive Safety Analysis for 2010 {CSA 2010]) 

that places a greater emphasis on more frequent interactions with motor carriers. 

9. Vehicle, motor carrier, and commercial driver identifiers, as well as 

compliance (i.e., weight, safety, credential) data are sent to a back-office 

repository so the State can develop a history of compliance/noncompliance with 

weight standards for each motor carrier and/or commercial vehicle (similar to 

the safety performance metrics calculated by FMCSA). 

10. Weather data from the vehicle is sent to system operators for real-time traffic 

management. 

4-10 
Concept of Operations for Virtual Weigh Station 

4-11

11. Localized and real-time traveler information is sent to the commercial vehicle 

for integration with on-board systems designed to display this information safely 

and with a minimum amount of driver distraction. 

12. Data from the VWS is available to authorized users for planning and 

reporting purposes. 

13. Data from the VWS is available to motor carrier users for tracking of the 

company’s assets and their performance. 
Concept of Operations for Virtual Weigh Station 

Figure 4.4 Expanded Virtual Weigh Station Concept of Operations 

10,11

Mainline

Bypass Route

6

Traffic Management Center

State Data Center

1

2,3

5

4, 9

6

7 

10, 11

8, 12, 13 

Motor Carrier

8, 13

FMCS

4-12 
Concept of Operations for Virtual Weigh Station 

4.5 ARCHITECTURE

Figures 4.5 and 4.6 provide high-level overviews of the proposed system 

architecture for basic and expanded VWS systems. The basic VWS architecture 

in Figure 4.5 includes two groupings – one for Roadside technology components 

and another consisting of back-office components grouped into a State Data 

Center. The expanded VWS architecture in Figure 4.6 adds a third grouping 

called External User Services, which provide for additional VWS 

operations/support capabilities for external users. These three architecture 

groupings are further defined as follows: 

 Roadside—This grouping includes the set of technologies and operations 

that involve the identification, observation, and enforcement interaction with 

the commercial vehicle and the driver. Baseline core VWS technologies 

include AVI transponder vehicle identification, camera systems, and WIM 

scales. Expanded VWS roadside technologies include driver identification 

technologies (e.g., biometrics, smart cards), OCR systems (e.g., LPRs and 

USDOT number readers), and dimensional sensors. 

 State Data Center—This grouping provides the set of information 

technology systems and databases that enable the functionality of the VWS 

system. The State Data Center referenced in the context of this ConOps is a 

multi-agency data system fusing information stores maintained by 

Departments of Transportation or Highway Agencies, Departments of Motor 

Vehicles, State Enforcement Agencies, and State Revenue Agencies 

supporting high-speed information exchanges at roadside enforcement sites. 

In the basic VWS scenario, only a repository of transponder identifiers would 

be hosted in the State Data Center. Expanded VWS functionality is largely 

based on the increased amount of data/factors that can be queried at the 

roadside and/or stored from the roadside. As such, the expanded VWS 

scenario has several additional components that would be hosted at a State 

Data Center, including: 

– CVIEW—repository of motor carrier, commercial vehicle, and 

commercial driver safety and credential information that can be queried 

to support the real-time screening at the roadside. CVIEW also could 

store wireless roadside inspection data that is collected from a VWS. 

CVIEW also serves as the conduit to exchange data to/from other 

jurisdictions and FMCSA. For instance, CVIEW is the means by which a 

State gains access to FMCSA’s screening algorithm data, as well as other 

states’ IRP and IFTA status information. Many State CVIEWs also store 

other commercial vehicle credentials (e.g., OS/OW permit, intrastate 

vehicle registration) that can be accessed in real-time at the roadside; 

– Warning/citation generation—back-office process that could generate 

warning letters and/or citations to a motor carrier if a commercial vehicle 

is found to be noncompliant by a VWS; and 

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Concept of Operations for Virtual Weigh Station 

4-14 

– Historical size and weight compliance database—back-office application 

that records a motor carrier’s long-term compliance with Federal and 

State size and weight regulations, in order to support planning activities, 

as well as development of warning letters. 

 External User Services—This grouping encompasses future potential uses of 

VWS information to support public and private sector operations. Motor 

carriers would be provided with time-stamped vehicle location information 

that could support enhanced productivity, as well as tailored traveler 

information. Transportation management centers would receive tailored 

information concerning roadway congestion and conditions. Through 

CVIEW, State and Federal safety systems would receive key enforcement 

data outputs. State enforcement agencies would also receive key statistical 

information that could assist them in better planning for VWS deployment 

across a State. 

The arrows connecting each of the components in Figures 4.5 and 4.6 illustrate 

the specific information interfaces for the VWS architecture. In general, the 

Roadside elements identify and weigh the commercial vehicle, as well as conduct 

enforcement activities. The screening computer integrates data from the 

Roadside systems and vehicle and uses this data to query (in the expanded 

scenario) data from the State Data Center in order to screen and target vehicles at 

the roadside. The screening computer also relays the data from the commercial 

vehicle and Roadside elements to enforcement personnel stationed at a fixed site 

or in a mobile unit. These enforcement personnel conduct roadside enforcement 

activities on targeted vehicles. 

In addition to providing data to be queried by the screening computer, the State 

Data Center systems also provide the outputs necessary to support the External 

Users of the VWS data (e.g., traffic management centers, motor carriers, Federal 

safety systems, planning offices). State Data systems also could generate 

automatic citations and record a motor carrier’s historical compliance with size 

and weight regulations. In this construct, at a point in the future, two-way 

communication also could facilitate actual communication between the truck and 

back-office and External User systems. 

Boxes shown in white are components of the basic VWS concept. Boxes shown 

in gray are components of the expanded VWS concept. The box shown in green 

is indicative of a future system (e.g., 5.9 GHz) that could support two-way 

communication between a commercial vehicle and back-office systems. 
Concept of Operatio

Figure 4.5 Basic Virtual Weigh Station Interfaces 

Roadside

WIM Scale

AVI System

Camera

System

Screening 

Computer

Commercial 

Vehicle

Mobile 

Enforcement 

Detail

Fixed Inspection 

Station

Sta
Concept of Operations for Virtual Weigh Station 

Figure 4.6 Expanded Virtual Weigh Station Interfaces 

Roadside External User Servic

Motor Carriers

State Data Center

WIM Scale

Transponder ID 

Repository AVI System

Traveler Info, 

Vehicle 

Location Data, 

Citation Data

Camera System

Driver ID 

Technology

2-way Comm. 

Upgrade

USDOT 

Number Reader

CVIEW

Historical Size 

and Weight 

Compliance 

Database

Transportation 

Management Center

Congestion 

Monitoring

National Safety System

SAFER, 

PRISM, CSA 

2010, other

State Enforcement 

Planning

Mobile 

Resource 

Planning

Screening 

Computer

Commercial

Vehicle Warning/Citation Generation

Mobile 

Enforcement 

Detail

Fixed Inspection 

Station

Dimensional 

Sensors

License Plate 

Reader

4-16 
Concept of Operations for Virtual Weigh Station 

4.6 COMMON STEPS

There are five basic steps that are shared between the two operational scenarios: 

 Identify commercial vehicle—An accurate and timely identification of the 

commercial vehicle is at the core of all VWS functionality. The vehicle 

identification ensures that the proper vehicle is screened and/or targeted for 

additional enforcement activities. Most states that have augmented the basic 

camera system with AVI functionality currently are using LPRs to identify 

commercial vehicles. Performance of LPRs has been uneven and remains 

under investigation. Some states have reported LPR accuracy rates of 85 

percent while others have reported rates as low as 30 – 50 percent. A variety 

of operational (e.g., speed, placement of license plate, ink used on license 

plate) and environmental (e.g., shadows, glare, weather) issues directly 

impact the effectiveness of these systems. Concerned about the long-term 

viability of LPRs as the identification technology, some states have begun to 

investigate alternate detection systems for use in their roadside enforcement 

systems. For instance, New York is investigating the use of 5.9 GHz 

(IntelliDrive/Vehicle Infrastructure Integration [VII]) technology, and 

Tennessee is studying the use of a cellular/satellite communication system. 

Other applications (e.g., tolls) also have begun to migrate towards 

inexpensive passive (“sticker”) tags that are affixed to vehicle windshields. 

FHWA is initiating a new project to identify which technology is best suited 

to attain its long-term objective of identifying all commercial vehicles in realtime at highway speeds. 

 Weigh commercial vehicle—Like vehicle identification, accurately weighing 

a commercial vehicle is a core component of any VWS. The accuracy of the 

gross vehicle weight or axle weight estimate can be affected by the WIM scale 

technology in use. When installed on the mainline, more expensive WIM 

systems have less variance in their readings and may better compensate for 

filtering external factors that affect vehicle weight calculations. Conversely, 

less expensive WIM scales or sensors may not be as accurate at highway 

speed. An example of a low-cost WIM device that has been deployed in the 

United States is the piezoelectric sensor. More recently, several states have 

begun including quartz piezo WIM systems in their programs because of the 

acceptable level of accuracy these sensors produce. Quartz piezo WIM 

devices, like electric piezos, are relatively inexpensive and not difficult to 

install but feature a short service life, especially on routes with high truck 

volumes. More expensive systems like load cell and bending plate offer 

higher accuracy in weight estimates but are more expensive to procure and 

are significantly more intrusive to the pavement structure. Bending plate 

systems offer high accuracy but are quite difficult to maintain; their expected 

service life far outperforms piezo sensors. Load cell scales are very durable, 

feature a significantly longer service life than the other devices, if maintained 

4-17
Concept of Operations for Virtual Weigh Station 

properly, and are quite easy to maintain. The trade-off among “up-front 

cost,” expected service life, and ease of maintenance should be carefully 

worked through before procurements take place. Typically, accuracy rates 

for all of these devices range from 85 to 97 percent.

 Establish vehicle dimensions—Another aspect of truck enforcement is 

measuring the vehicle dimensions to determine compliance with length, 

width, or State-specific height requirements. Verification of vehicle 

dimensions for State-issued oversize permit compliance can be automated by 

deploying overhead gantry or roadside elevated laser scanning systems. 

Many commercial vendors have vehicle dimension technology bundled into 

their “off-the-shelf” virtual weigh station packages. The military has had 

vehicle dimension detection systems in operation for quite some time now to 

support rapid deployments. Recently, more advanced laser-based systems 

have been emerging, offering enhanced image quality and greater accuracy 

in determining vehicle envelopes.

 Determine screening decision—If a VWS is designed to support a manual 

screening model, the system simply delivers a photo of the vehicle and 

accurate weight information to a roadside enforcement resource in real-time. 

The system also may use color (i.e., a red border around the photo, red text 

for overweight data) to highlight an overweight vehicle. If a VWS is 

designed to automatically screen commercial vehicles based on a series of 

criteria (e.g., weight, safety algorithms, past compliance with size and weight 

standards), the screening software must be programmed to weigh the various 

criteria and determine what factor or combination of factors will yield a 

decision to target a commercial vehicle for further scrutiny. A similar 

approach (e.g., pre-determined weights are assigned to specific evaluation 

criteria with the sum total of the criteria yielding a pull-in/bypass decision) is 

used to support electronic screening in some states.

 Share data—Conceptually, a VWS is designed to take data from a 

commercial vehicle and share it with authorized users. In the basic VWS 

concept, only vehicle identification (either via a transponder or a photo) and 

weight data is shared and enforcement personnel are the only authorized 

personnel authorized to access this data. In the expanded VWS concept, a 

larger amount of data is shared between the commercial vehicle and the 

roadside and a broader range of authorized users can access specific types of 

data. The expanded data being shared from the commercial vehicle includes 

vehicle identification via OCR, driver identification, weather data, and 

operational data. Further with the expanded VWS concept, data also may be 

shared from the roadside (e.g., truck parking information, traffic/traveler 

advisories) to the commercial vehicle and from back-office systems to the 

motor carrier (e.g., tracking data, citation data). Regardless of the type or 

amount of data being shared, the VWS concept provides a platform that 

serves as a conduit for information sharing.

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Concept of Operations for Virtual Weigh Station 

4.7 OPERATIONAL POLICIES

While VWS deployments vary widely by states, the following policies 

summarize the minimum policies that should be enacted by all states deploying 

VWS technology: 

 All commercial vehicles must be identified and weighed by a VWS; 

 Commercial vehicles should be allowed to proceed at the normal speed for 

the road on which they are operating when passing a VWS; 

 Deployment of VWS technology should be designed to limit driver 

distraction; 

 VWS deployments should leverage existing information technology (IT) and 

data infrastructure and standards (e.g., a State’s CVISN systems, existing 

WIM deployments) whenever possible; 

 Motor carriers should be made aware of how data collected by a VWS will be 

used; 

 Access to VWS data should be limited to authorized users that have a clear 

and pertinent business need for the information (e.g., roadside enforcement 

personnel to support screening decisions, motor carriers to track their own 

vehicles); 

 Motor carriers should be provided with a means to challenge any data that 

they believe to be inaccurate; 

 Direct enforcement and/or a change to a motor carrier’s safety rating will 

occur only if the VWS data (e.g., motor carrier/vehicle identification, weight 

information) can be certified as being accurate; 

 Standards should be developed to govern the storage and retention (e.g., how 

long will data be kept) of all data associated with VWS deployments; and 

 Data used by government agencies for non-enforcement purposes (e.g., 

planning) should be anonymous. 

4.8 IMPACTS

Deployment of VWS technology has the potential to fundamentally change the 

way truck size and weight standards and regulations are enforced in the United 

States. Anticipated impacts include: 

 All commercial vehicles subject to electronic screening—Current 

deployments of electronic screening are voluntary in nature (i.e., motor 

carriers determine if they wish to participate and thereby install a 

transponder). VWS deployments are designed to enable the screening of all 

commercial vehicles. This “100 percent” screening would be attained by the 

reading of identifiers that all commercial vehicles are required to have (i.e., 

4-19
Concept of Operations for Virtual Weigh Station 

license plate, USDOT number) or through the adoption of a new technology 

that all commercial vehicles would be required to install. With respect to 

current identifiers, additional research and refinement of technology are 

required to achieve 100 percent accuracy in reading commercial vehicles. 

 Improved operational efficiency for enforcement personnel—VWS 

technology has the potential to dramatically improve the efficiency and 

effectiveness of the nation’s size and weight enforcement regime. Currently, 

less than one percent of commercial vehicles that are weighed at the roadside 

are found to be overweight. While this is in part a testimony to the number 

of legal carriers operating in the United States, it also is an indication that 

noncompliant carriers are successful in bypassing enforcement activities. 

VWS deployments will allow roadside enforcement personnel to target their 

efforts at commercial vehicles that are known to be operating over legal 

limits and allow compliant carriers to avoid roadside enforcement stops. 

VWS deployments also have the potential to exponentially expand the 

geographic scope of a State’s enforcement program and limit the number of 

routes on which a noncompliant vehicle can operate without being detected 

and/or monitored by enforcement personnel. This improved efficiency is a 

key factor in states’ decisions to deploy VWS technology, especially given the 

budget constraints under which many states currently are operating. 

 More frequent verification of commercial vehicle compliance—The use of 

automated systems will allow for the frequent verification of commercial 

vehicle compliance with Federal and State size and weight regulations, as 

well as safety and credentialing regulations (if expanded VWS functionality 

is deployed). These more frequent inspections will be enabled by the 

deployment of enforcement assets (i.e., VWS) on bypass roads and in 

remote/urban areas that currently cannot accommodate roadside 

enforcement actions. More frequent inspections also will be supported by the 

24X7 operational nature of VWS, as opposed to the shift deployments 

associated with human assets. Expanded VWS functionality (i.e., 

maintenance of a historical size and weight compliance database, issuance of 

warning letters/citations, targeting of motor carriers that regularly operate 

beyond legal limits) also will improve motor carrier compliance even in cases 

where enforcement personnel cannot be dispatched to execute a roadside 

inspection based on VWS data. Enforcement interventions (e.g., warning 

letters, company visits, inspections) also could be utilized on noncompliant 

carriers that cannot be addressed in real-time when fixed inspection sites 

become occasionally overwhelmed by commercial vehicle traffic, which 

likely will happen even if 100 percent of commercial vehicles could be 

identified electronically. 

 Improved mobility for compliant motor carriers—VWS technology will 

continually verify the compliance of all commercial vehicles with Federal and 

State regulations but only target enforcement resources at high-risk motor 

carriers and commercial vehicles. This robust targeting will ensure that 

4-20 
Concept of Operations for Virtual Weigh Station 

4-21

compliant commercial vehicles will avoid being stopped for a roadside 

inspection even though their compliance with Federal and State regulations 

will frequently be checked. The targeting will save time and money for 

compliant carriers while disproportionately delaying unsafe and 

noncompliant carriers, which should encourage compliance and ensure that 

noncompliant carriers do not enjoy an operational advantage over compliant 

carriers. 

 Greater geographic enforcement coverage from limited financial 

resources—Many states continue to struggle with deep budget crises that are 

requiring them to seek alternate and more cost-effective means of doing 

business. Deployment of VWS has the potential to improve the efficiency of 

states’ roadside enforcement programs while reducing the costs associated 

with the deployment and operation of roadside assets. 

 Development and maintenance of new data interfaces—The greatest 

benefits from VWS technology will be achieved through the deployment of 

expanded VWS functionality that will leverage deployments to monitor 

compliance with both size/weight and safety/credentialing regulations. In 

order to support this expanded functionality, interfaces must be developed 

and maintained from the roadside to the State’s CVISN architecture. CVISN 

is a national initiative designed to share safety and credentialing information 

across jurisdictional boundaries; it provides a rich repository of safety and 

credentialing data for the screening of commercial vehicles and targeting of 

high-risk commercial vehicles and motor carriers. Other Federal programs 

(e.g., Performance and Registration Information Systems Management 

[PRISM], Comprehensive Safety Analysis for 2010 [CSA 2010]) also can 

provide data to support the real-time screening of commercial vehicles. A 

forum to discuss these interfaces is provided through FMCSA’s Expanded 

CVISN Roadside Identification Ad Hoc Team, in which FHWA, states, 

industry, and other parties also participate. 

 Development of new targeting data—Numerous targeting resources (e.g., 

ISS, PRISM, Safety Status Measurement System [SafeStat], CVIEW) exist to 

focus enforcement resources on carriers with poor histories of safety 

performance and/or noncompliance with credentialing regulations. At this 

point, there is no similar electronic repository of past performance data for a 

carrier’s compliance with Federal and State size and weight issues and as 

such, resources cannot be targeted at commercial vehicles operated by motor 

carriers that routinely operate overweight. FHWA and FMCSA could discuss 

the possibility to leverage the existing CVISN architecture to provide this 

information. Similarly, one of the new Behavioral Analysis Safety 

Improvement Categories (BASICs)—Improper Loading/Cargo—that will be 

at the core of FMCSA’s CSA 2010 program may provide a means to target 

enforcement resources at carriers that are routinely noncompliant with size 

and weight standards. 

Concept of Operations for Virtual Weigh Station 

5-1

5.0 Summary of Benefits and 

Costs 

5.1 BENEFITS

While no formal evaluation of VWS has been completed, anecdotal information 

and evaluation results from deployments of similar roadside applications 

provide examples of the wide range of benefits that likely will accrue to public 

and private sector stakeholders by VWS. These benefits include: 

 Increased protection and preservation of pavement and the nation’s 

infrastructure—Overweight trucks are estimated to cause hundreds of 

millions of dollars in damage to the nation’s roadways each year. Virtual 

weigh stations have the potential to dramatically reduce the damage done to 

the roadways by overweight vehicles operating illegally (i.e., without a valid 

OS/OW permit) by expanding the geographic scope of the nation’s truck size 

and weight enforcement programs and deploying enforcement assets into 

areas currently not monitored by fixed or mobile enforcement resources. 

Recent research indicates that an 80,000 pound commercial vehicle has the 

equivalent single axle load (ESAL) value of 26,000 passenger vehicles, while a 

100,000 pound commercial vehicle has the same ESAL value as 70,500 

passenger vehicles.9 As such, every illegally operating, severely overweight 

(at least 20,000 pounds greater than the legal limit) truck that can be removed 

from the roadways has the same impact on the infrastructure as removing 

44,500 passenger vehicles from the traffic flow. State estimates suggest that 

reducing the number of overweight trucks will save tens of millions of 

dollars. Arizona estimates that overweight trucks cause $12 million to $53 

million in damage to the State’s infrastructure annually.10 A similar study 

conducted in 1999 found that overweight vehicles in Texas caused an 

estimated $6 million to $48 million in damage to the State’s roads and bridges 

annually.11 In addition to reducing this excessive damage to the nation’s 

 

9 American Association of State Highway Transportation Officials (AASHTO), Virtual 

Weigh-in-Motion: A “WIM-win” for transportation agencies,

http://www.transportation.org/sites/aashtotig/docs/021907%20Short%20Version.pdf

, February 2007. 

10 Eric Volante, “Overweight Trucks Damage Roads, Bridges,” The Arizona Daily Star, 

September 11, 2007. 

11 “Keeping overweight trucks from getting a-weigh,” Texas Transportation Researcher,

Volume 35, No. 3. 
Concept of Operations for Virtual Weigh Station 

5-2 

infrastructure, virtual weigh stations also may increase overall compliance 

with size and weight regulations because commercial vehicles may be unable 

to avoid enforcement resources as easily in the future and their operators will 

therefore be more willing to “voluntarily” comply.

 Increased efficiency of enforcement assets—Enforcement personnel 

continue to be overwhelmed by the number of commercial vehicles operating 

in the United States and the volume of trips made by these vehicles. Between 

1990 and 2006 (the most recent year for which data is available), vehicle miles 

traveled by large trucks increased by 53 percent and the number of large 

trucks registered in the United States increased by 42 percent.12 The sizeable 

increase in the number and volume of commercial vehicles to be regulated 

occurred without a corresponding increase in enforcement personnel. As a 

result, the time between inspections and roadside weighings of commercial 

vehicles has increased. Further, the potential for a commercial vehicle to 

avoid enforcement has increased in recent years as commercial vehicles elect 

to use bypass routes to avoid fixed inspection stations and are less likely to 

encounter mobile enforcement personnel. Virtual weigh stations have the 

potential to address these issues by extending a State’s enforcement program 

to bypass and secondary routes and focusing its limited human enforcement 

assets on commercial vehicles that are known to be overweight or have other 

increased risk factors (e.g., operated by a carrier with a poor history of safety 

performance). In addition, VWS data can be used to more effectively 

schedule enforcement resources and ensure that human assets are deployed 

at locations/days/times when data indicates there is an increased occurrence 

of overweight trucks. This improved efficiency of enforcement personnel 

also will benefit legally operating commercial vehicle operators because it 

will serve to “level the playing field” and ensure that some operators are not 

deriving an unfair competitive advantage by operating illegally. 

 Improved highway safety—The recently completed national evaluation of 

the Commercial Vehicle Information Systems and Networks (CVISN) 

program included an in-depth analysis of the safety benefits that could be 

derived from the increased use of roadside enforcement technologies and the 

increased targeting of commercial vehicle operators with histories of poor 

safety performance. This analysis revealed that the nationwide deployment 

of roadside technologies (e.g., infrared brake testers, safety algorithms 

associated with high driver OOS rates) could result in as many as 17,907 

fewer crashes and 215 fewer fatalities per year than if the inspection selection 

process was based solely on manual (human) screening.13 Expanding the 

 

12 Large Truck Crash Facts 2006, Federal Motor Carrier Safety Administration, January 

2008, page 4. 

13 CVISN National Evaluation Report, Volume 1, Federal Motor Carrier Safety 

Administration, 2008, page 7-13. 
Concept of Operations for Virtual Weigh Station 

5-3

number of technology-equipped sites through the deployment of virtual 

weigh stations with expanded functionality should directly support these 

safety results.

 Improved operations/turnaround time—As part of the national CVISN 

evaluation, 848 motor carriers were interviewed to document their 

experiences using CVISN services, including the program’s electronic 

screening functionality. Similar to VWS, electronic screening targets 

enforcement resources at high-risk commercial vehicles based on a series of 

screening factors (e.g., weight, safety performance) and roadside technologies 

(e.g., WIM, AVI). Nearly 98 percent of motor carrier respondents indicated 

that they had experienced “reduced delays” based on their participation in 

the program. Nearly 80 percent of motor carrier respondents also reported 

reduced labor costs associated with their use of electronic screening.14 Based 

on the similarity of the VWS and electronic screening concepts, a similar 

percentage of motor carriers interacting with VWS likely will derive 

operational benefits from this technology.

 Improved freight data for planning—Having access to accurate data 

regarding the movement of commercial vehicles across the transportation 

system is a key component of effective and accurate transportation planning, 

especially freight planning. These data are used to identify corridors that 

support commercial vehicle traffic, as well as to provide inputs to travel 

demand models that forecast the impact of a change to a region’s 

infrastructure. The freight planning community currently is beginning to use 

data from wireless technology providers (e.g., satellite, cellular) to capture 

vehicle-specific movements, as well as general corridor-level freight flows 

and/or system performance. Virtual weigh stations, especially those with 

expanded functionality, have the potential to generate and provide this type 

of data to planners and those responsible for overall system performance. 

 Improved air quality— Idling long-haul trucks are estimated to “consume 20 

million barrels of diesel fuel and generate 10 million tons of CO2, 50,000 tons 

of nitrogen oxides, and 2,000 tons of particulates annually.”15 While most of 

this environmental impact is caused by commercial vehicles idling overnight, 

the targeting of enforcement resources at high-risk motor carriers and 

commercial vehicles should reduce air quality costs associated with trucks 

idling while waiting for roadside inspections. The PrePass electronic 

clearance program estimates that over 309,000 metric tons of carbon 

emissions have been prevented through its bypass program, which currently 

 

14 CVISN National Evaluation Report, Volume 1, Federal Motor Carrier Safety 

Administration, 2008, page 5-13. 

15 Argonne National Laboratories, “Reducing Heavy Truck Idling,” 

http://www.transportation.anl.gov/engines/idling.html. 
Concept of Operations for Virtual Weigh Station 

5-4 

is deployed at over 280 sites and has 413,224 commercial vehicles enrolled.16 

A nationwide deployment of similar technologies (i.e., VWS) has the 

potential to substantially increase these benefits. 

 Improved asset tracking—VWS technologies and other roadside 

enforcement technologies can generate the requisite data (e.g., vehicle 

identification, date, time, location) to allow a motor carrier to track its 

commercial vehicles’ movements. To date, motor carriers have expressed 

minimal interest in accessing VWS data for the purpose of asset tracking 

because 1) they already use private sector service providers for this function 

and 2) there are concerns about timeliness and robustness of the data. As 

VWS is deployed more widely, motor carriers may express an increased 

interest in this functionality.

5.2 COSTS

VWS is a low-cost alternative to expanding a State’s truck size and weight 

enforcement program. Costs associated with VWS deployments vary by the 

scope of the VWS being deployed, the amount of existing infrastructure that can 

be leveraged by a State, as well as the type of technology being deployed. Based 

on requests to FMCSA for Federal CVISN Deployment funds, estimated costs of 

recent VWS deployments are between $300,000 and $1,400,000.17 Even the highend costs are much lower than the costs associated with building a new fixed 

weigh station, which typically costs $12 million but can cost as much as $300 

million if land acquisition is required. 

5.3 AVAILABLE FUNDING SOURCES

Various funding sources are available to support the deployment of VWS. These 

funding sources include: 

 Federal-Aid Highway Program (FAHP)—Deployment of WIM systems in 

conjunction with a VWS deployment may be an eligible FAHP expense. 

FAHP funding eligibility is determined by the primary intended purpose and 

use of the WIM. Construction of WIM systems “that directly facilitate an 

effective vehicle weight enforcement program” are eligible for FAHP funding 

as defined under “construction” in Section 101(a)(3)(H) of Title 23, United 

States Code (USC). 

 

16 PrePass website, www.cvo.com, June 18, 2009. 

17 Data is from State applications for Federal CVISN Deployment Grant applications, 

Fiscal Years 2006-2008. 
Concept of Operations for Virtual Weigh Station 

5-5

 State Planning and Research (SP&R) program—WIM systems that are built 

to primarily support the statewide traffic monitoring program for uses 

including analysis of travel and weight trends, pavement and bridge 

monitoring and management, and pavement design, qualify for funding 

through the State Planning and Research (SP&R) program. These WIM sites 

can be used secondarily by enforcement personnel for resource planning and 

commercial vehicle weight screening. 

 Commercial Vehicle Information Systems and Networks (CVISN)—In the 

past few years, over a dozen states have used Federal CVISN Deployment 

Grant funds to implement virtual weigh stations. Among components of the 

virtual weigh station that are eligible expenses for CVISN funding are WIM 

scales, cameras, OCR technology, system electronics, screening software, and 

system integration. A State’s CVIEW system, which is an eligible CVISN 

expense, also can serve as a key data repository in support of VWS 

deployments (e.g., serve as a database of motor carrier and commercial 

vehicle safety and credentials data that can be queried by the VWS screening 

system, serve as a repository for data collected from the VWS). CVISN funds 

also can be used to support expanded communication networks to support 

the timely and secure transmission of virtual weigh station data to users, as 

well as integration of safety data/screening algorithms into roadside 

operations. 

Many states’ WIM systems originated as part of FHWA’s Strategic Highway 

Research Program (SHRP) or Long-Term Pavement Performance (LTPP) 

Program. These programs, focused on pavement research, placed an emphasis 

on collecting locally- or segment-specific vehicle loadings. Some states have 

upgraded the WIM systems originally used only for data collection to contain 

screening capabilities, as found in virtual weigh stations, at relatively low cost. 

Traffic monitoring functions have remained intact, while the addition of 

screening capabilities is attractive to the State’s enforcement agency and 

optimizes the utility of the WIM equipment. If consideration is given to using 

existing WIM sites to support roadside enforcement, a State must be diligent in 

ensuring that an off-road location is available for enforcement officials to conduct 

more extensive weighing activities safely removed from the traffic stream should 

a roadside inspection be warranted. 

Concept of Operations for Virtual Weigh Station 

6.0 Conclusions 

6.1 SUMMARY OF IMPROVEMENTS

As previously noted, virtual weigh stations have the potential to: 

 Improve operational efficiency and effectiveness of states’ roadside 

enforcement programs by targeting resources at commercial vehicles that are 

known to be overweight, are known to be operated by carriers with histories 

of poor safety performance and/or compliance with Federal and State size 

and weight regulations, or are currently noncompliant with Federal and/or 

State credentialing regulations; 

 Expand the geographic scope of a State’s roadside enforcement program to 

limit the number of roads on which a noncompliant commercial vehicle can 

operate without being detected by an enforcement resource; 

 Improve motor carrier compliance with Federal and State truck size and 

weight regulations; 

 Improve motor carrier safety through improved enforcement and a reduction 

in the number of operating overweight commercial vehicles; 

 Improve productivity of compliant motor carriers through a reduction in the 

number of roadside inspections to which they are subjected; 

 Provide an additional source of tracking information for motor carriers; 

 Reduce fuel consumption by legally loaded and operating carriers caused by 

unnecessary delays at weigh stations; 

 Reduce costs associated with new roadside enforcement assets due to the cost 

differential between deployment of a VWS and a fixed weigh station; 

 Improve real-time data sharing with commercial vehicles; 

 Provide a rich source of weather and traffic information for system managers; 

and 

 Provide augmented data sources for use by freight and highway planners. 

6.2 DISADVANTAGES AND LIMITATIONS

While there currently are no known disadvantages to the deployment of VWS 

technology, the current state of technology does limit the applications that can be 

supported by these systems. These limitations include: 

 Universal identification of commercial vehicles currently is not possible—

The only identifiers that currently are common to all commercial vehicles are 

6-1
Concept of Operations for Virtual Weigh Station 

license plates, vehicle identification numbers, and USDOT numbers (for 

interstate motor carriers, as well as intrastate motor carriers in states 

participating in the PRISM program). Unfortunately, these devices were 

designed to be read by a human and not by a machine/automated system. 

License plate readers and USDOT number readers use a combination of 

cameras and OCR to interpret these visually-based identifiers into data that 

can be used as part an automated system. The accuracy of the current LPR 

and USDOT reader technology varies widely due to operational and 

environmental factors and prohibits all commercial vehicles from being 

identified by VWS systems at this time. Research is continuing to refine the 

camera hardware, as well as the OCR software, to improve the reliability of 

these systems but some states are concerned that optically-based VWS will 

never be able to achieve the goal of 100 percent identification. 

 Human interaction is still required—A variety of technical (e.g., accuracy of 

current WIM technology) and institutional/legal factors dictate that VWS 

technology serve only as a screening and planning tool for roadside 

enforcement personnel. VWS deployments currently require that a human 

issue a citation for any overweight or compliance issue that may be detected. 

As such, despite the presence of VWS technology a State’s enforcement 

capacity remains limited to the number of enforcement personnel that are on 

duty at one time in a given region. These enforcement resources can be 

easily overwhelmed by the number of noncompliant vehicles operating in a 

region thereby reducing the overall utility and effectiveness of the 

technology. 

6.3 NEXT STEPS

In order to overcome the current technical/operational limitations affecting the 

effectiveness of VWS deployments, the following should be pursued: 

 Develop architecture for “e-Permitting/Virtual Weigh Stations”—With the 

complexity of the data model, business case, and overall use case associated 

with “e-Permitting/VWS,” schematics and diagrams are needed to identify 

and document data production and storage aspects supporting enforcement 

and truck support services at the roadside platform. Data interrelationships 

can be identified, eliminating unnecessary duplication of information 

employed by the wide array of automated systems operating at the roadside. 

Data flows enabling all Title 23 and Title 49 of the United States Code truck 

checks and measurements coupled with State permit verifications, revenue 

agency oversight interests, and truck company and driver services, need to 

be mapped in a comprehensive roadside architecture model providing 

insights that could enhance system performance and deliver Smart Roadside 

Initiative program objectives.

 Determine which vehicle identification technology is best suited to 

identify all commercial vehicles—A variety of research is underway to 

6-2 
Concept of Operations for Virtual Weigh Station 

6-3

determine the suitability of LPR, USDOT number readers, 900 MHz 

transponders, passive transponders, 5.9 GHz radios, cellular, and satellite 

technologies to achieve the goal of identifying 100 percent of commercial 

vehicles in real-time at highway speeds. Each of these technologies has 

unique strengths and weaknesses. For instance, while license plate readers 

currently do not offer 100 percent accuracy, they are based on an identifier 

(license plate) that is required on all commercial vehicles and for which there 

is an existing process of distribution and renewal (i.e., the registration 

process). Conversely, passive transponders, while offering 100 percent 

accuracy in identification, currently do not have a process by which they can 

be distributed. The FHWA universal truck identification project is designed 

to consider these operational and implementation issues and provide greater 

clarity regarding which technology offers the greatest potential to accurately 

identify all commercial vehicles at the roadside within three to five years. 

The benefits/costs associated with mandating a technology also will be 

evaluated. 

 Conclusively document the benefits of VWS—The benefit data associated 

with VWS deployments currently is derived from evaluations of related 

systems/programs (e.g., electronic screening, CVISN). In order to encourage 

future deployments of VWS and ensure that deployments are delivering their 

intended benefits, FHWA should commission a formal evaluation of the VWS 

concepts. To the extent possible, the evaluation should isolate the relative 

benefits and costs associated with basic and expanded VWS components so 

that states can determine which VWS elements they want to deploy. 

 Investigate the deployment of direct enforcement concepts in the United 

States—The real compliance, safety, and operational benefits of VWS will be 

seen if the United States is able to move towards a direct enforcement regime 

using advanced technology. Several countries in Europe currently employ 

direct enforcement based on the data from their WIM scales. Similarly, some 

jurisdictions in the United States use direct/photo enforcement for red-light 

running and driving through an automated toll lane without a transponder. 

An alternative to the current VWS model would include a gross vehicle and 

axle or axle set weight detection system capable of determining vehicle and 

axle weights with enough accuracy to enable the issuance of citations for 

violations. Further, research into the institutional and legal implications 

associated with issuing citations and/or warnings based on an automated 

system also should be studied. Precedents and lessons learned from other 

direct enforcement applications (e.g., red-light running cameras) should be a 

key part of this research. 

Concept of Operations for Virtual Weigh Station 

Appendix – Acronyms 

AASHTO American Association of State Highway and Transportation Officials

AVI Automatic Vehicle Identification

BASIC Behavioral Analysis Safety Improvement Categories

ConOps Concept of Operations

COST Cooperation in Science and Technology

CSA Comprehensive Safety Analysis

CVIEW Commercial Vehicle Information Exchange Window

CVISN Commercial Vehicle Information Systems and Networks 

DOT Department of Transportation

ESAL Equivalent Single Axle Load

ETA Estimated Time of Arrival

FAHP Federal-Aid Highway Program

FHWA Federal Highway Administration

FMCSA Federal Motor Carrier Safety Administration

GHG Greenhouse Gas 

GHz Gigahertz 

HSWIM High-Speed Weigh-in-Motion 

IFTA International Fuel Tax Agreement

IRP International Registration Plan

ISS Inspection Selection System 

IT Information Technology

LPR License Plate Reader 

A-1
Concept of Operations for Virtual Weigh Station 

A-2 

LTPP Long-Term Pavement Performance

MHz Megahertz

NCHRP National Cooperative Highway Research Program

OCR Optical Character Recognition 

OOS Out-of-Service Order 

OS/OW Oversize and Overweight 

PRISM Performance and Registration Information Systems Management

SAFER Safety and Fitness Electronic Records

SafeStat Safety Status Measurement System

SHRP Strategic Highway Research Program

SP&R State Planning and Research

TIG Technology Implementation Group 

TMC Traffic Management Center

UCR Unified Carrier Registration

USC United States Code

USDOT United States Department of Transportation 

VII Vehicle Infrastructure Integration

VIN Vehicle Identification Number

VMT Vehicle Miles Traveled 

VWS Virtual Weigh Station

WIM Weigh-in-Motion 

WIM-VID Weigh-in-Motion and Visual Identification 
Technical Report Documentation Page 

1. Report No. 

FHWA-HOP-09-051 

2. Government Accession No. 3. Recipient’s Catalog No. 

5. Report Date 

June 2009 

4. Title and Subtitle 

Concept of Operations for Virtual Weigh Station 

6. Performing Organization Code 

7. Author(s) 

Steve Capecci, Cathy Krupa, Cambridge Systematics, Inc. 

8. Performing Organization Report No. 

9. Performing Organization Name and Address 10. Work Unit No. 

Cambridge Systematics, Inc. 

100 CambridgePark Drive, Suite 400 

Cambridge, MA 02140

11. Contract or Grant No. 

DTFH61-06-D-00004 

13. Type of Report and Period Covered 

Final Report 

12. Sponsoring Agency Name and Address 

Federal Highway Administration 

Office of Freight Management and Operations 

1200 New Jersey Avenue, SE 

Washington, DC 20590 

14. Sponsoring Agency Code 

15. Supplementary Notes 

FHWA COTM: Tom Kearney 

16. Abstract 

This document describes the concept of operations (ConOps) for the virtual weigh station (VWS). The 

ConOps describes the goals, functions, key concepts, architecture, operational scenarios, operational 

policies, and impacts of virtual weigh stations. This ConOps will provide technical guidance to 

jurisdictions regarding their implementations of the virtual weigh station concept and will be a tool that 

can be used to plan roadside programs, support states’ funding requests, obtain buy-in from public and 

private stakeholders, and communicate information among State, Federal, and private sector parties. The 

document consists of six sections: 

1. Section 1.0, Introduction – Provides the context for developing a concept of operations for the virtual 

weigh station. 

2. Section 2.0, Current Situation – Reviews current roadside enforcement operations and existing 

virtual weigh station deployments. 

3. Section 3.0, Motivation for Virtual Weigh Station – Describes the challenges and needs underlying 

states’ virtual weigh station deployments and the operations that will address the challenges. 

4. Section 4.0, Concept of Operations – Presents the operational scenarios, information needs, and 

functionality associated with virtual weigh stations. 

5. Section 5.0, Summary of Benefits and Costs – Relates the expected benefits and costs of deploying 

virtual weigh stations. 

6. Section 6.0, Conclusions – Summarizes the enforcement improvements gained from virtual weigh 

stations, as well as limitations and next steps. 

17. Key Words 

Commercial vehicles, trucks, virtual weigh 

stations, concept of operations 

18. Distribution Statement 

No restrictions. 

19. Security Classif. (of this report) 

Unclassified 

20. Security Classif. (of this page) 

Unclassified 

21. No of Pages 

60 

22. Price 

Form DOT F 1700.7 (8-72) Reproduction of completed pages authorized