2.0 Summary of Benefits and Challenges
In Task 2 of this project, FHWA and Cambridge Systematics interviewed stakeholders from nine states that are at the forefront of the deployment of roadside enforcement systems. Site visits were conducted in four of these states. During the course of these interviews and visits, several standard applications of roadside technologies were identified. These standard deployments include:
Previous project tasks have described the benefits associated with deploying roadside technologies. Roadside technologies and their key benefits are summarized below.
Traffic Monitoring WIM Systems
Mainline WIM systems are commonly used to collect traffic characteristics information for analysis of travel and weight trends, pavement and bridge monitoring and management, pavement design, and development of emissions models; this information is used by the State transportation or highway agency. Additionally, some states’ enforcement agencies use the WIM information to make more effective use of enforcement resources, assigning personnel based on occurrences of recorded weight violations. Historical data from WIM systems can be used to focus inspections at locations where noncompliant and overweight trucks are known to travel. Factors such as levels of truck traffic and frequency of overweight trucks at a site broken down by day and time of day are used to determine the most productive locations, days, and times for scheduling mobile enforcement teams.
Data on CMV travel patterns could be used to determine the most commonly traveled freight corridors, for example, to support Federal and State freight planning initiatives. Vehicle dimension data could be used by FHWA to identify the highways that carry the largest number of commercial vehicles, as well as the heaviest annual loads. This data could be integrated with existing pavement and bridge management processes, in order to target maintenance funding at high-traffic/high-weight/high-risk corridors.
Mobile Screening at WIM Sites
In a typical mobile screening environment, an enforcement 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 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. Mobile screening makes it much easier to identify overweight trucks. In fact, having quantifiable performance measurements (i.e., individual axle weights and gross vehicle weights) avoids stopping vehicles that are legal according to weight thresholds established by the State. Moreover, screening keeps the industry moving by not weighing trucks that are legally loaded.
Mobile screening at WIM sites provides increased opportunity for enforcement by providing added capacity for resources, allowing for enforcement that is not disruptive to the travel stream, and guaranteeing more efficient delivery of enforcement actions through targeted intervention. In many cases, WIM systems chiefly used for data collection can be upgraded to contain mobile screening capabilities at relatively low cost. Traffic monitoring functions (e.g., availability of data for State and Federal planning purposes) 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. These WIM sites may be located in areas currently not monitored by fixed or mobile enforcement resources, or new WIM systems may be installed for the same reasons – to expand the geographic scope of the State’s truck size and weight enforcement program and remove illegally operating, overweight trucks from the roadways. As a result, mobile screening operations help to protect and preserve the roadway infrastructure, improve safety, and level the playing field for safe and legal carriers.
Virtual Weigh Stations
A virtual weigh station is similar to a mobile screening site, but a VWS includes the addition of a camera system, at minimum, and possibly additional technologies, such as a LPR or USDOT number reader. While in use for enforcement purposes, both a mobile screening site and a VWS require human monitoring of the real-time data generated by the WIM installation. A VWS deployment, compared to mobile screening, does not require the monitoring officer to be positioned at or near the WIM site. The addition of a camera allows an officer to be located at a much greater distance from the site, affording lower visibility of enforcement activities. The same data and images viewed by an officer located downstream of the WIM site may be viewed by enforcement personnel in a fixed facility. Instead of an officer located downstream performing monitoring and weighing functions, personnel viewing the WIM data and images at another location such as a central office or weigh station could dispatch nearby enforcement units to intercept and weigh suspect vehicles identified on the monitor.
Flexibility in the positioning of the patrol vehicle was mentioned by several states participating in the project as a key advantage of digital imaging deployment at a VWS. Furthermore, in areas with high truck volumes, a suspect vehicle can be identified by its photo integrated with its WIM record. A LPR or USDOT number reader can be deployed to provide the VWS with digital image capture and identification through 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. LPRs and USDOT number readers are forms of AVI. 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. AVI deployment allows screening on safety, credentials, and criminal justice information as well as weight by associating WIM readings and can considerably reduce the time required to retrieve additional information about a suspect vehicle.
Benefits that accrue to stakeholders from VWS deployment are described below. These benefits are similar to the benefits associated with mobile screening.
Fixed Site-Based Mainline Weight Screening
WIM systems are used to screen vehicles on the mainline (ML) for weight compliance as they approach a weigh station. Trucks that exceed the threshold are directed into the weigh station to be weighed on more accurate static scales used to write citations. Mainline weight screening produces a number of benefits. Weigh-in-motion significantly increases the capacity of weigh stations. In the absence of mainline WIM, queues may form and cause closure of weigh stations; as a result, compliance checks are not performed on the bypassed vehicles. WIM also reduces congestion within the fixed weigh station facility; focuses enforcement on high-risk operators, thereby increasing enforcement personnel’s effectiveness; and provides time savings for safe and legal carriers, supporting more efficient movement of freight. The reduced number of trucks that idle and stop as they enter the weigh station queue to be weighed on the static scale also improves air quality.
When used as part of an electronic screening or bypass system such as PrePass or NORPASS, WIM provides real-time weight verification concurrent with safety and credentials verification for bypass eligibility. Data (e.g., vehicle identification, date, time, location) are generated by these deployments that can allow a motor carrier to track its vehicles’ movements. Additional benefits of mainline weight screening deployments include the availability of WIM data for freight planning and other State and Federal monitoring, tracking, and screening purposes.
WIM scales are also installed on weigh station ramps to weigh and sort vehicles at low speeds. Vehicles that have left the main highway move to the approach ramp where they are weighed by a ramp, or sorter, WIM. The ramp WIM sorts the arriving trucks based on a weight threshold set by weigh station personnel. Axle spacing, vehicle height, and vehicle classification also may be determined. Vehicles that do not exceed the threshold are signaled by a message sign to move to the bypass lane for return to the main highway. Remaining vehicles are directed to the static scale for weighing.
Ramp sorting combined with a bypass lane can process more vehicles than could be supported by static weighing alone. Several states participating in the project reported that they plan to install additional sorter WIM systems in order to increase throughput at the weigh station. While not as effective as mainline WIM in reducing delays for safe and legal carriers and vehicles, ramp systems provide a much quicker alternative to static scale processing.
Table 2.1 summarizes the benefits of the various roadside technologies and identifies the stakeholder groups that accrue the benefits.
Despite the potential of advanced technologies to dramatically improve the effectiveness and efficiency of roadside enforcement operations, a number of challenges commonly confront states that attempt to deploy these systems. These challenges include:
These challenges are described below. Strategies that have been employed successfully by states to overcome these challenges are presented in Section 3.0. Program support that needs to be offered by FHWA to help states overcome these challenges are presented in Section 4.0.
WIM systems vary considerably in cost. An example of a low-cost WIM device that has been deployed in the United States, especially for traffic monitoring purposes, is the piezoelectric sensor. Recently, several states have begun including quartz piezo WIM systems in their programs because of their usefulness in truck enforcement activities. Quartz piezo WIM devices, like electric piezos, are relatively inexpensive and not difficult to install. One State participating in the project reported the cost per lane of piezoelectric WIM as $16,000, the cost of quartz piezo WIM as $29,000, and the cost of bending plate WIM as $40,000. Another State reported the cost per lane of a single load cell system as $87,500. Comparatively expensive systems like load cell and bending plate also are significantly more intrusive to the pavement structure. However, the expected service life of the WIM instrument is greater with higher cost. The accuracy of weight estimates reported for quartz piezo, bending plate, and single load cell systems is about 95 percent; piezoelectric accuracy rate is lower, at about 85 percent.
When WIM systems are used for screening purposes, additional cost elements are required that can substantially raise deployment costs. Most costly is construction of a new weigh station with mainline WIM screening and/or ramp sorting capabilities. Construction, equipment, and operations and maintenance (O&M) costs were identified by participating states as a primary reason states are not building new weigh stations. A “typical” weigh station can cost $12 million to build. If land must be purchased, the cost of a new weigh station can approach $300 million. In comparison, adding a mainline WIM system to an existing weigh station is a fraction of the cost.
Virtual weigh stations are a low-cost alternative to a new weigh station. 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 Commercial Vehicle Information Systems and Networks (CVISN) Deployment funds, estimated costs of recent VWS deployments are between $300,000 and $1,400,000. (Data is from State applications for Federal CVISN Deployment Grant applications, Fiscal Years 2006-2008.) Even the high-end costs are much lower than the costs associated with building a new fixed weigh station. At the lower cost range, a basic VWS consists of WIM (which may be new or existing, thereby affecting the cost), a camera system, and high-speed communications. At the upper cost range, an expanded VWS includes WIM, AVI (such as a license plate reader or USDOT number reader), multiple database linkages, enhanced screening algorithm, and additional technologies.
Deployment of mobile screening at a WIM site is less costly than a virtual weigh station. “Limited incremental costs” were reported by one State for upgrading a WIM site from traffic monitoring data collection only to enforcement (screening). A more robust WIM site with four lanes of new quartz sensors, WIM controller, roadside cabinet, radio frequency transmitter and receiver, and utilities was reported to cost $160,000.
Owing to the very high cost of constructing, operating, and maintaining a weigh station, many states are turning to mobile screening and virtual weigh stations to increase the scope of enforcement activities at less cost and staff than are required by weigh station operations. As states deployed these non-traditional forms of enforcement, they found considerable benefits, to the point where several states reported that better results in identifying overweight trucks were obtained by using WIM sites, either through mobile screening or virtual weigh stations, because of the greater coverage afforded by these WIM applications.
Arguably the most labor intensive roadside operations are weigh stations, which must support a complement of size, weight, and safety specialists on a continuous basis when the weigh stations are open. Mainline weight screening and ramp sorting using WIM systems automate much of the process of weighing vehicles approaching or entering weigh stations, but staff still are needed to interact with vehicles that must be weighed on the static scale. For a new weigh station, personnel previously assigned to other duties will be needed to operate the new facility, drawing officers away from existing operations, including mobile patrols.
Inasmuch as virtual weigh stations today serve only as screening tools for roadside enforcement personnel, VWS deployments require that a human weigh a truck and 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.
States participating in the project emphasized that sufficient staffing is critical in any enforcement operation, whether the operations take place at weigh stations, where staffing tends to be continuous, or at WIM sites (as mobile screening) or virtual weigh stations, which do not require continuous staffing, but where resources are necessary to monitor, intercept, and take enforcement action on commercial vehicles.
Benefits from deploying roadside technologies accrue most noticeably when technologies are combined. In fact, the Task 1 deliverable (“American Lego diagram”) illustrated how roadside technologies could be combined to improve the efficiency and effectiveness of various elements of the roadside enforcement process in the United States. The experiences of the states participating in the project provided real-world examples of improving enforcement operations through the integration of technologies.
Many states support weigh stations equipped with mainline and/or ramp WIM, as well as traffic monitoring WIM systems. In a relatively simple enhancement, traffic monitoring WIM sites are upgraded or retrofitted with Wi-Fi (wireless fidelity) connectivity, a transmitter/receiver, a laptop capable of handling data, and software that can display the WIM data, to support real-time weight screening. A camera system and enhanced communication capability and computer software can be added to the WIM site to allow a vehicle to be identified by its photo integrated with its WIM record, as part of a virtual weigh station. Further, virtual weigh stations can be enhanced with automatic vehicle identification that can provide an automated screening decision based on linkages with vehicle, safety, and security databases and screening algorithms.
The challenges facing a State that seeks to deploy systems with multiple technologies, whether by adding on to existing systems or building complex systems anew, are technical and institutional. Virtual weigh stations that support digital imaging, AVI, automatic access to commercial vehicle data, and advanced screening algorithms, for example, rely on a well-designed architecture with documented systems interfaces, data flows, and communications networks. More often than not, it will be a challenge to integrate the technologies into one system. It also is a challenge to deploy the system with one user interface. As additional technologies (e.g., radiation detection, infrared brake sensing) are added, there is a tendency to add user interfaces (computer screens) to the mix of operations. According to one participating State, any project with multiple technologies will have this problem. Regardless, the goal is to minimize the number of interfaces that enforcement personnel have to monitor.
Interagency cooperation is crucial to the success of non-traditional enforcement applications such as mobile screening and virtual weigh stations. The importance of interagency teamwork was expressed by several states as an essential requirement for deploying virtual weigh stations because of the need to involve the State’s transportation or highway agency, chief enforcement agency, and motor vehicle agency in designing the deployment. The multiple technologies associated with the virtual weigh station rely on a team concept for successful deployment, according to one of the participating states. Interagency cooperation also is essential to ensure multiple objectives are met when deploying a new mainline WIM application in the vicinity of a weigh station. Enforcement needs as well as data collection needs should be coordinated during planning and design. Mobile screening often utilizes existing traffic monitoring WIM systems that have been upgraded to enable real-time weight screening. The new enforcement needs, as well as new equipment (e.g., communication capability), must be integrated with the existing data collection functions. In many cases, the interests of multiple agencies are involved and these agencies must work together to establish an effective and mutually beneficial WIM application.
Motor carriers expressed concerns about the data generated from roadside enforcement technologies in interviews conducted in Task 5. These concerns involve data retention, usage, and privacy. The issues are described briefly below.
Performance issues with AVI technologies commonly used in advanced virtual weigh stations can jeopardize the widespread deployment of virtual weigh stations as a means to identify and screen all commercial vehicles. The only identifiers that currently are common to all CMVs are license plates, vehicle identification numbers, and USDOT numbers (for interstate motor carriers, as well as intrastate motor carriers in states participating in the Performance and Registration Information Systems Management [PRISM] program). These identifiers were designed to be read by a human and not by a machine or automated system. Because of this limitation, and operational and environmental factors related to these OCR technologies frequently used in virtual weigh stations, LPRs and USDOT number readers are not currently able to accurately identify 100 percent of CMVs that are screened.
While in-cab transponders are commonly used for AVI at fixed sites in association with electronic screening with excellent results, they have not been deployed at virtual weigh stations because system operators want to screen all CMVs, not only the modest number of vehicles with transponders. As most experts believe that accuracy will never approach 100 percent because license plates and displayed USDOT numbers are not standardized and not optimized for automated reading, it may be necessary for the stakeholder community to establish a universal, electronically readable identifier for commercial vehicles. It is within this context that the Federal Highway Administration is undertaking a universal truck identification project that will encourage the implementation of a technology that can accurately identify all CMVs at the roadside.
WIM technologies in use today for screening provide 85 to 95 percent accuracy of highway speed weight estimates. States that have deployed virtual weigh stations report the performance of WIM systems as excellent for screening purposes. However, inasmuch as greater accuracy will result in fewer trucks that require static weighing, which will conserve resources and eliminate delays for more trucks, higher performing WIM systems will be a considerable benefit to states. For direct weight enforcement to be adopted in the United States, 100 percent accuracy in determining a vehicle’s weight will be necessary. As such, current WIM technology cannot support direct enforcement in the United States.
Lack of funding is a major impediment to the deployment of virtual weigh stations and other roadside technologies. Federal CVISN funds currently are the primary source of funding that states are pursuing to support the deployment of virtual weigh stations. To date, 14 states have applied for CVISN funds for this purpose. While this is an effective source of funds with favorable rules regarding the State/private sector match that is required, several factors may impact its utility.
First, the CVISN Deployment Grant program is only authorized through Federal Fiscal Year (FY) 2009, which concludes on September 30, 2009. While FMCSA has requested an extension of this program, the future of the funding program will not be determined until Congress completes the highway bill reauthorization. Second, states can only receive a combined $3.5 million in Federal funding to support its CVISN program under TEA-21 and SAFETEA-LU. A handful of states already have reached this limit and therefore are ineligible to receive additional Federal funding to support their CVISN programs. Even if the CVISN program is reauthorized as part of the new highway legislation, this $3.5 million ceiling could limit the utility of the funding source for some states. Finally, states are required to deploy basic (i.e., Core) functionality as part of the CVISN program. This Core CVISN functionality (e.g., electronic credentialing, safety information exchange, and electronic screening) may require all of a State’s available CVISN funding and therefore not leave sufficient funding to support the deployment of additional functionality (i.e., virtual weigh stations).
Lack of Standards/Architecture
The CVISN Architecture “identifies the general vehicle, general driver, and CVO-unique aspects of the National ITS Architecture.” (Commercial Vehicle Information Systems and Networks (CVISN) System Design Description, The Johns Hopkins University Applied Physics Laboratory, June 2009, page 10. “ITS” refers to Intelligent Transportation Systems.) While states have a great deal of flexibility in determining how to deploy CVISN functionality, the National CVISN Architecture with its pre-defined interface standards and data models ensures that data can be shared effectively and accurately across jurisdictional boundaries. An architecture has the following high-level benefits:
Relatively new roadside operations such as virtual weigh stations do not have an established architecture. This makes it difficult for various jurisdictions to achieve consistency in designing and deploying technologies, communications, software, interfaces, and user services. Communication about a “virtual weigh station” frequently causes confusion as different jurisdictions conceptualize VWS differently.In view of the increasing number of virtual weigh station deployments without a common framework, FHWA in Task 2 of this project directed the development of a concept of operations (ConOps), including a high-level architecture, for the virtual weigh station. The ConOps will be available in June 2009. previous | next
United States Department of Transportation - Federal Highway Administration