This paper was prepared for the ITS America Seventh Annual Meeting, June 2 - 5, 1997, Washington, D.C.

Commercial Vehicle Operations (CVO) Electronic Screening System for the State of Missouri—Implementation through Current ITS Technologies


Bill McCall
Director of Advanced Transportation Technology
Center for Transportation Research and Education (CTRE)

Marilyn Kuntemeyer
Senior Project Manager
Center for Transportation Research and Education (CTRE)


The State of Missouri is actively pursuing a project that will allow commercial vehicles to have electronic screening service available at the weigh/inspection stations along major highways throughout the state with the application of currently available Intelligent Transportation Systems (ITS) technologies. With this electronic screening concept, vehicles that are safe and legal and have no outstanding out-of-service citations will be able to pass the weigh/inspection facility without delay. The Missouri ITS/Commercial Vehicle Operations (CVO) project proposes to combine technologies currently used in electronic toll collection (ETC) with a fiber optic communication system available along 350 miles of interstate highway in Missouri.

Commercial vehicles traveling the Oklahoma and Kansas Turnpikes often travel through Missouri as well, and both turnpike authorities have adopted Electronic Toll and Traffic Management (ETTM) processes and technologies that include the use of Automatic Vehicle Identification (AVI) transponders (tags) to pass through toll facilities without delay. This provides an opportunity to bundle ITS/CVO services with ITS/ETC services in compatible vehicle-to-roadside communication systems.

This paper presents the following information: existing conditions for commercial vehicle operations and the communications infrastructure in Missouri; a discussion of tag technologies; architecture of the proposed Missouri Electronic Screening System; and current status of planning and implementation.

Key Words: CVO, ITS, Electronic Screening, Weigh Stations


State agencies in Missouri are interested in the application of intelligent transportation systems technologies to improve the efficiency and safety of commercial vehicle operations (CVO). The CVO vision shared by state agencies in Missouri is the same as the National Intelligent Transportation Systems (ITS) Program Plan developed by ITS America for the Federal Highway Administration (FHWA). The vision is "Assisted by advanced technology, trucks and buses will move safely and freely throughout North America." The applied technology will take the form of electronic screening that will enable transponder-equipped trucks and buses to have safety status, credentials, and weight checked at mainline speeds. Vehicles that are safe and legal and have no outstanding out-of-service citations will usually be allowed to pass the weigh/inspection facility without delay.

The Missouri Department of Transportation (MoDOT) and the Missouri State Highway Patrol (MSHP) have jointly undertaken a number of initiatives to "promote the economic well-being of Missouri and the nation by facilitating goods movement for business, industry, and motor carriers." In addition to the Kansas-Missouri ITS Institutional Issues Study conducted at the request of MoDOT, Missouri has developed an ITS/CVO Standing Committee at the state level including all agencies contributing to commercial vehicle operations. The ITS/CVO Standing Committee is charged with implementation of the Memorandum of Agreement (MOA) for ITS/CVO that has been signed by the directors of the following organizations: 1) MoDOT; 2) MSHP; 3) Missouri Department of Revenue (MDOR); 4) Missouri Department of Economic Development; 5) Missouri Division Office of the FHWA; 6) Office of Motor Carriers of the FHWA; and 7) Missouri Motor Carriers Association. This MOA has also been signed by the governor of the state of Missouri.

Missouri has also been successful in obtaining participation from the private sector for support of ITS/CVO programs. In cooperation with MoDOT, a private company has laid several hundred miles of fiber optic cable in the highway rights of way throughout the state. MoDOT and MSHP have participated in the design and installation of the network to provide for nodes at weigh stations throughout the state. Once completed, the entire communications infrastructure will be in place with the capability to link the MSHP’s mainframe computers to the fixed weigh stations. The fiber optic network will provide the avenue required to process data transmission at the speeds necessary for electronic clearance of commercial vehicles traveling at mainline highway speeds.


Primary responsibility for motor carrier regulation and credentialing is shared by four agencies in the state of Missouri: 1) MoDOT; 2) MDOR; 3) Missouri Department of Economic Development, Division of Motor Carrier and Railroad Safety (MCRS); and 4) MSHP.

[Note: state agencies in Missouri changed the names of some organizations during 1996. The Missouri Highway and Transportation Department (MHTD) became the Missouri Department of Transportation (MoDOT), and the Division of Transportation (MDOT) in the Department of Economic Development became the Division of Motor Carrier and Railroad Safety (MCRS). Documents published prior to 1997 will refer to these organizations using the previous names of MHTD and MDOT.]

MoDOT administers the oversize/overweight (OS/OW) permit program in the state of Missouri. Carriers wishing to operate a vehicle that exceeds Missouri dimensional or weight limits must obtain an OS/OW permit for that vehicle. Carriers moving loads exceeding 120,000 pounds Gross Vehicle Weight (GVW) may be subject to bridge stress studies, which are conducted by the DOT.

The MDOR oversees several motor carrier functions including vehicle titling and registration (including the International Registration Plan, or IRP, for interstate carriers); motor fuel taxes (International Fuel Tax Agreement or IFTA); commercial drivers licensing; and the issuance of temporary permits. In conjunction with these functions, the MDOR is responsible for accepting and reviewing applications, issuing credentials to approved carriers, and auditing and collecting fees when required.

The MCRS Division in the Department of Economic Development is responsible for regulating common, contract, and private motor carriers in the state of Missouri. Motor carriers that fall into one of these categories and conduct intrastate or interstate operation must obtain operating authority from the MCRS. MCRS operating authority may be granted to motor carriers who are registered with the Interstate Commerce Commission (ICC), as well as to ICC-exempt carriers.

The MSHP enforces the credentials issued by the agencies listed above and operates all fixed and mobile enforcement facilities. The MSHP is also responsible for administration of the Motor Carrier Safety Assistance Program (MCSAP) funded by FHWA. Weight and safety enforcement is the responsibility of the MSHP's Commercial Vehicle Enforcement (CVE) Unit. Vehicles may be weighed at fixed inspection stations located throughout the state or by mobile inspection units. The CVE Unit also conducts vehicle and driver inspections. Enforcement personnel have the authority to put drivers out of service for certain vehicle or driver safety violations, or for operating without the proper credentials.

Under the current weight enforcement strategy, all trucks must stop at weigh stations when the scales are open. This causes unnecessary delays for legal carriers, and the requirement for all of the trucks to exit and enter the traffic flow may have a negative impact on safety. Under the current enforcement system, driver and vehicle credentials cannot be inspected without the truck stopping, either at a weigh station or a roadside spot check. Requiring all trucks to stop, whether or not they are operating legally, dilutes the effectiveness of enforcement efforts and reduces carrier productivity.

The State of Missouri currently operates weigh stations at 19 locations as shown in Figure 1. During 1995, the Center for Transportation Research and Education (CTRE) conducted a study for Missouri to focus on the enforcement activities that currently take place at the permanent weigh stations and to investigate Automatic Vehicle Identification (AVI) technologies that could be easily implemented for electronic screening at the weigh stations along I-70 and I-44.

Table 1 shows general traffic flow information at the weigh stations on these two interstate highways through Missouri. I-70 carries the highest volume of truck traffic with more than 7,500 trucks using this route each day, and I-44 is the second busiest with truck volumes over 6,000 per day.

A communications infrastructure is also in place that can serve the weigh stations along I-44 and I-70. Figure 2 shows the extent of the fiber optic network for ITS communications that has been developed along highway rights of way throughout Missouri. The fiber optic network will provide the avenue required to process data transmission at the speeds necessary for electronic screening of commercial vehicles traveling at mainline highway speeds. The fixed weigh stations along I-44 and I-70 will be able to communicate with the mainframe computers of the Highway Patrol located in Jefferson City.

The Oklahoma and Kansas Turnpikes have adopted Electronic Toll and Traffic Management (ETTM) processes and technology that include the use of AVI transponders (tags) to pass through toll facilities without delay. Trucks operating on I-44 and I-70 in Missouri are often users of the Oklahoma and Kansas Turnpikes and may already have toll tags on the vehicles. Both turnpike authorities have selected a common technology so future customers will not have to purchase more than one tag and to assure compatibility between the toll facilities.

MoDOT decided to investigate the use of enhanced toll tags to facilitate electronic screening for trucks at weigh stations on I-44 and I-70. Because trucks operating on the Oklahoma and Kansas Turnpikes are likely to already have toll tags, the same identification tags could be used to identify trucks with valid and current Commercial Vehicle Safety Alliance (CVSA) safety inspections and with current and valid credentials. In conjunction with mainline Weigh-In-Motion (WIM), the opportunity appears to exist, at a minimum level of investment and risk (both financial and technical), to electronically screen trucks for current safety inspections and possibly for credentials and weight.

As a first step in determining if those toll collection transponders currently on commercial vehicles could support electronic screening at weigh stations, MoDOT first wished to know approximately how many tag-equipped trucks were currently passing the weigh stations. Field data were collected during the summer of 1995 in order to estimate the number of trucks passing weigh stations along I-44 and I-70 that are currently equipped with toll tags from either Oklahoma or Kansas.

During June 1995, an AVI reader system was placed along the side of the eastbound travel lanes of I-44 just before the exit ramp for the Joplin weigh station. Data were recorded from Monday, June 12, 1995 through Tuesday, June 20, 1995, and the highest number of tags recorded was more than 1,500 on Friday, June 16, 1995. The vehicles carrying tags from the Oklahoma Turnpike Authority (OTA) were easily identifiable in the tag numbers recorded, and the OTA tags ranged from 89 percent to 94 percent of the total number of tags recorded.

During the time period that the toll tags were recorded, traffic volumes from a nearby permanent count station showed eastbound travel on I-44 at approximately 8,000 vehicles on weekdays (range = 7,378 vehicles per day to 8,571 vehicles per day). Total traffic on Friday, Saturday and Sunday was substantially higher with volumes ranging from about 10,000 vehicles per day to more than 11,000. The percent of vehicles in the eastbound traffic flow with toll tags ranged from about 24 percent to 35 percent.

The toll tag counts on I-44 show that a significant number of vehicles are already carrying toll tags and have the potential to qualify for a CVO electronic screening program, but it cannot be assumed that all of the toll tags recorded were on commercial vehicles. An attempt was made to determine the exact number of OTA toll tags records that were actually on commercial vehicles. The Pike Pass of the OTA is sold for commercial vehicle accounts as well as those for private, passenger vehicles. Assistance was requested from both the manufacturer of the OTA toll tags and from officials at the OTA to see if these toll tag records could be sorted into groups of commercial vehicles and private, passenger vehicles. At present, due to legal constraints on the release of information, the OTA is unable to provide assistance that would allow more detailed sorting of the toll tag records.

The AVI reader system was also placed along the eastbound travel lanes of Interstate 70 at the Odessa weigh station from June 22 through July 10, 1995. The data records of the tag readings were not useable for the entire time period, but for the days with valid data, the number of toll tags recorded on I-70 ranged from 215 to 513 per day.

The number of vehicles equipped with toll tags is currently much higher along I-44 (with a maximum reading of more than 1,500) than along I-70 (with a maximum reading of slightly over 500). Vehicles from the Oklahoma Turnpike are not as likely to be traveling on I-70 since there is no direct connection from Oklahoma. Vehicles from the Kansas Turnpike are much more likely to be traveling on I-70, but the Kansas Turnpike Authority only began using ETTM during 1995 and penetration of the toll tags has not reached the level that is seen in Oklahoma. (The OTA has been using electronic toll payment since 1991). In general, the information collected about current toll tag use along I-44 and I-70 shows that a sufficient number of vehicles are currently equipped with tags to support building on this technology for CVO electronic screening.


The Oklahoma and Kansas Turnpikes have adopted ETTM processes and technologies that include the use of AVI transponders (tags) to pass through toll facilities without delay. Common to all Electronic Toll Collection (ETC) systems are a vehicle-mounted transponder/tag, a reading device, and a computer system for processing and storing data.

AVI or tag technologies and systems are often categorized as being either "Read Only" or "Read/Write." ETTM and CVO use the same terms to describe tag functionality. The three types of tags commonly envisioned to support electronic screening and ETTM applications are:

Type I - Supports only one-way transmission of an identifier or other fixed information from the transponder to the roadside reader.

Type II - Supports two-way data transmissions and, typically, a variable message component. This allows the transmission of variable data to the transponder at one reader (such as location identification and time stamp), and the subsequent transmission of that data from the tag to another reader.

Type III - Supports not only two-way transmission of data, but also supports electronic communication interfaces to external devices mounted on the vehicle, such as onboard computers. This allows data to be sent from an onboard computer to the tag, and from there transmitted to a roadside reader. Similarly, information from a roadside reader can be transmitted to the transponder and from there sent to an onboard computer or signaling device to be read by the truck driver.

The technological basis for transponder technology is not new. Its origins can be traced to the use of Identification Friend or Foe (IFF) interrogation employed during World War II. Aircraft detected by radar could not be readily identified as friendly; radio contact with the pilot could confirm the nature of the aircraft. However, in the absence of direct pilot confirmation, "friendly" could not be established. This problem was solved by placing a transponder in the friendly aircraft. As the aircraft entered radar range, the transponder was interrogated and a code was exchanged between the aircraft and security establishing the aircraft as friendly.

From that early beginning, tags can now be used to support electronic screening. The basic differences among various tag technologies lie in the communications medium, the sophistication of the communications protocol between tag and reader, and the extent of tag "intelligence." The majority of systems currently utilize some form of radio frequency identification (RFID) scheme to establish reliable communications between tag and reader. The carrier frequency of choice lies in the 902 - 928 MHZ band, but others operate as high as

2450 MHZ (2.45 GHz) and as low as 134 KHz. Radio Frequency (RF) tags can be further differentiated by whether they merely modulate the carrier signal (passive or backscatter tag) transmitted by the reader and reflect the signal back to the reader or contain an internal transmitter (active tag), capable of replying when the reader is not transmitting.

The Pike Pass tags of the OTA are Type I, and the Kansas tags are Type II. Both turnpike authorities have selected a common technology, backscatter, with the tags manufactured by Amtech.

Most major toll agencies in the United States either have Dedicated Short Range Communications (DSRC) systems in current revenue service or have made the decision to install DSRC and have selected a technical solution. By the end of 1994, approximately 500,000 tags were in use, by 1995 this number had doubled to 1 million, and by the end of 1996 it doubled again to 2 million. CVO applications currently include approximately 10,000 users on the two major CVO applications (HELP Inc. and Advantage I-75) as well as several border crossing projects on the borders of Texas, California, New York and Michigan.

The OTA began using electronic toll payment in 1991, and a 1996 survey by International Bridge, Tunnel and Turnpike Association (IBTTA) showed that the OTA had the largest number of ETC customer accounts. Based on March 1997 information provided by Amtech (letter dated 3/10/97), the OTA has approximately 332,000 customer accounts for ETC tags, of which about 75,000 are issued to accounts for commercial vehicles of a classification that would have to stop at weigh stations. The Kansas Turnpike Authority began ETC operations in late 1995 and currently has 65,000 customer accounts for toll tags. Fifty thousand of these Kansas accounts are for commercial accounts such as trucking or other service businesses. The Amtech tags used by Oklahoma and Kansas currently amount to almost 400,000 of the estimated 2 million customer accounts (about 20 percent) that are in place nationwide for ETC operations.

Tag technologies have evolved, and continue to evolve, on the basis of technological advancements and market requirements. Various standards setting activities are currently underway, and Missouri plans to evaluate both the existing RFID population and other tag technologies as the state moves forward with implementation of electronic screening.


The term "architecture" is used in many contexts with varying definitions. For research currently being conducted for ITS, the overall structure (i.e., major components and interfaces) and unifying design characteristics (i.e., principles and standards) of a system are referred to as the architecture of that system. This section will describe a general architecture for electronic screening for the state of Missouri. The architecture is intended to provide guidance to implementers of the CVO electronic screening system.

The MSHP currently verifies the following information when trucks come through the weigh stations:

1) Vehicles are weighed to check for compliance with weight limits, and if overweight, the vehicle is checked for a valid OW permit from MoDOT;

2) Vehicle credentials may be checked to verify that the vehicle has all necessary permits to operate in the state of Missouri;

3) Vehicle credentials may be checked to verify that the vehicle has paid fuel tax and has a fuel permit;

4) Driver credentials may be checked to verify that the driver has a valid Commercial Driver's License (CDL) to operate a commercial vehicle in the State of Missouri; and

5) Vehicle inspection may occur to determine if the vehicle meets all applicable vehicle safety codes.

Under the current weight enforcement procedures, all trucks must stop at weigh stations in Missouri when the scales are open. The credentials of trucks and drivers cannot be inspected without the truck stopping, either at a weigh station or a roadside spot check. Table 2 lists the credential check and inspections actions that could be accomplished by the screening of information on a transponder or by automated field review.

Figure 3, Typical Weigh Station Configuration, shows the configuration that could be used at a typical weigh station that combines Weigh-In-Motion (WIM) scales with AVI readers of transponders that contain data elements about the truck passing the weigh station. Through the WIM scale and AVI reader shown in Figure 3, many credential checks and inspection actions could be accomplished by verification of information on a transponder or by automated field review.

In order to accomplish the screening actions listed in Table 2, information exchange will need to be accomplished very effectively. Figure 4, Information Exchange Architecture for State Motor Carrier Functions, illustrates the information exchange that will be required for the motor carrier functions of the State of Missouri. Information exchange will be required between the following state government agencies involved in motor carrier functions: MDOR, MoDOT, and MSHP.

Figure 5 shows the general architecture of the proposed Missouri Electronic Screening System and identifies subsystems that Missouri can evaluate for implementation. The illustration is organized beginning at the Roadway AVI and WIM subsystem and flowing to the subsystem of the processors at the weigh stations. The weigh station processors then connect to the processors at the state, regional and national levels.


Missouri will consider two alternatives to support implementation of the Roadway AVI and WIM subsystem for electronic screening:

1) Missouri owning the Roadway AVI and WIM subsystem; and

2) Missouri contracting with a company to provide the data necessary to support the Roadway AVI and WIM subsystem for electronic screening.

Although many options could be considered for this subsystem of electronic screening, ownership and contracting are the two major alternatives. Other options could include contracting for only certain elements of the Roadway AVI and WIM subsystem, such as training or maintenance.

If Missouri decides to pursue ownership of the Roadway AVI and WIM subsystem, this will include purchasing the equipment, either installing or contracting the installation, commissioning the subsystem, and maintaining the subsystem. Contracting for the service will include the establishment of an agreement with a company to provide the data necessary to support roadside electronic screening. In either case, Missouri will make a financial and technical resource investment.

A first step toward conducting a financial analysis which will support the decision that Missouri either own the subsystem or contract for data, is identifying the associated cost elements. Table 3, Roadway AVI and WIM Subsystem Cost Elements, identifies cost elements to consider when making the decision to either own this subsystem or contract for data. In Table 3, the Cost Elements are subdivided into non-recurring and recurring. Non-recurring costs are typically incurred once during the program, and periodic charges are incurred for recurring costs. Each of the cost elements is discussed in the following paragraphs.

The non-recurring costs include the following elements:

The recurring costs include the following elements:

If Missouri decides to pursue a contract agreement with a service provider, this will relieve Missouri of the responsibility for major non-recurring and recurring tasks. However, establishing a contract with a service provider will require that Missouri conduct a very focused effort in contract administration. For example, the contract must clearly establish the time period for the service provider to replace failed equipment and to have malfunctioning software back in operation. Further, the Missouri contract administrator must make sure the service provider meets the downtime specification in the agreement. Therefore, although Missouri will be relieved of subsystem facility maintenance and upgrading, Missouri’s contract administrator must assertively follow up on service provider performance levels established in the contract agreement.

During the coming year, the State of Missouri will be actively working on implementation of a CVO Electronic Screening System that builds on toll tag technology. This will include a bid process that will allow the state to perform financial evaluation of ownership versus contracting for service.


  1. National Program Plan for Intelligent Transportation Systems (ITS), Final Draft, November 1994.
  2. Kansas-Missouri ITS Institutional Issues Study, Final Report (December 1994) by Cambridge Systematics, Inc. with WHM Transportation Engineering, Inc.
  3. Kansas-Missouri ITS Institutional Issues Study, Final Report (December 1994) by Cambridge Systematics, Inc. with WHM Transportation Engineering, Inc.
  4. Fact Sheet on "Electronic Toll Collection in the U.S." from the ITS America Information Clearinghouse, June 8, 1995.
  5. Migration Plan for Dedicated Short Range Communications, prepared by PB Farradyne, Inc., Working Draft, January 6, 1997.
  6. ETTM System Survey, April 1996, International Bridge, Tunnel and Turnpike Association (IBTTA).

TABLE 1. Traffic Volumes at Missouri Weigh Stations on I-44 and I-70

Highway Route Identification Highway Patrol ID / Location of Weigh Station 1993 Average Daily Traffic (All Vehicles) 1994 Average Daily Truck Traffic
Number Percent of Total Traffic


C-2 / St. Clair



21 %

D-1 / Strafford



22 %

D-4 / Joplin



39 %


A-3 / Odessa



32 %

C-4 / Foristell



8 %

Source: Traffic volumes supplied by Missouri Department of Transportation

TABLE 2. Credential Checks and Inspection Actions

Credential, permit or inspection action Agency that issues permit Potential for tag screening or automated field review

Missouri-based registration or IRP registration with carrier apportioned for Missouri travel?

MDOR and


Tag screening

Driver trip permit if IRP Registration not apportioned for Missouri travel?


Tag screening

Does GVW comply with state law?

Truck weighed at station; no permit issued

Automated field review

OS/OW permit if truck GVW or size does not comply with state law?


Tag screening

ICC or ICC-exempt authority?


Tag screening

IFTA credentials or trip permit?


Tag screening

Valid driver's CDL?


Tag screening

Bill of lading match load?

No permit

Field inspection

Hazmat waste license and manifest?

Federal Highway Administration (FHWA)

Tag screening

Visible safety defects?

No permit

Field inspection

Driver's log current?

No permit

Future tag

Driver has driving time remaining?

No permit

Future tag

Driver has physical qualification certificate or physical waiver?


Future tag

TABLE 3. Roadway AVI & WIM Subsystem Cost Elements

Cost Element Cost Elements included by Alternative
Missouri Ownership Contract
Non-Recurring Costs










Subsystem Test



Subsystem Commissioning



Training for Operation



Training for Subsystem Maintenance



AVI & WIM Site Rehabilitation



Recurring Costs

Outside Services (i.e., telecommunications)



Technical Staff & Support for Subsystem Maintenance

  • Engineers & Technicians
  • Test Equipment
  • Repair Parts
  • Vehicle
  • Travel



Preventive Maintenance

  • AVI
  • WIM Calibration
  • Site Maintenance



Corrective Maintenance



Subsystem Upgrades

  • Equipment (site & transponder)
  • Software



Periodic Contract Charges



Contract Administration



Figure 1 Locations of Weigh Stations in Missouri

Figure 2 Fiber Optic Network for ITS Communications

Figure 3 Typical Weigh Station Configuration

Figure 4 Information Exchange Architecture for State Motor Carrier Functions

Figure 5 Proposed Electronic Screening Systems

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