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U.S. Department of Transportation U.S. Department of Transportation Icon United States Department of Transportation United States Department of Transportation

Public Roads - Autumn 1995

Advantage I-75. Prepares to Cut Ribbon on Electronic Clearance

by Joe Crabtree


 Long lines of trucks waiting to be processed at state weigh stations may soon be a thing of the past thanks to advanced technology currently being tested on Interstate 75 and Canadian Highway 401. The Advantage I-75 Operational Test Project is using a system called MACS (Mainline Automated Clearance System) to process trucks electronically, thus eliminating the need to stop at multiple weigh stations during a trip in this corridor. With MACS, participating trucks can have their weight and credentials checked at highway speeds without exiting the mainline. The system began operating more than a year ago at four sites in Kentucky, but the two-year operational test officially begins in October 1995, when all 30 weigh stations on the corridor will be equipped with the system.

Trucking participants in the project are volunteers, selected from a list of applicants based on their safety records and vehicle inspection programs. A total of 4,500 trucks will participate in the test, representing a wide variety of trucking operations.




I-75 and Highway 401 form a major international trade and goods movement corridor, which is one of the longest and busiest for trucking on the continent. Truck volumes are in excess of 4,500 per day throughout the corridor from Toronto to Detroit to Miami a distance of nearly 3,200 kilometers (km). Trucks represent from 20 to 35 percent of the daily traffic on most interurban segments of the route. Truck traffic on I-75 and Highway 401 exceeds 9 billion vehicle km annually. The total annual value of motor carrier operating expenditures in the corridor has been estimated to be more than $7 billion. It is clear that the corridor is vitally important in the transportation of goods and services.

Inspection stations, or weigh stations, are an important element in motor carrier administration and enforcement. These stations provide the opportunity for state enforcement personnel to check the vehicle's weight, dimensions, and credentials and to ensure that the vehicle is safe to operate. In addition, the driver's condition and operating records can be checked. This process can take anywhere from a few minutes to nearly an hour, depending on the weigh station configuration, the volume of trucks being processed, and whether or not the truck is inspected. Many weigh stations are unable to accommodate the high truck volumes passing through the stations; this results in frequent backups, long delays, and uncontrolled bypassing when ramps are full.

Weigh station stops are costly for truckers and, therefore, for consumers who use the product transported by truck. Time spent waiting in line, being weighed or inspected, or reviewing paperwork is non -productive time that results in a loss of efficiency and productivity. Deceleration, idling time, and acceleration result in higher fuel consumption and additional air pollution. The merging and diverging required at weigh station ramps creates a safety concern, particularly when long lines of trucks back up onto the mainline.

What is Advantage I-75?

Advantage I-75 is a partnership of public and private interests along the I-75 corridor. The goal of the partnership is to reduce congestion, increase efficiency, and enhance the safety of motorists and other users of I-75 (and its connections in Canada) using advanced vehicle and highway technologies. These technologies are usually referred to as Intelligent Transportation Systems (ITS). The Advantage I-75 partnership has sought to identify areas where ITS technologies can be applied quickly to achieve immediate benefits.

The Advantage I-75 partnership had its beginnings in June 1990, when a concept conference was held in Lexington, Ky., to discuss the feasibility of conducting an ITS project for commercial vehicle operations on I-75. Conference participants endorsed the concept and formed a policy committee to guide development of the project.

Project partners include the Federal Highway Administration, the six I-75 states (Florida, Georgia, Tennessee, Kentucky, Ohio, and Michigan), the province of Ontario, the Canadian Ministry of Transport, U.S. and Canadian trucking associations, and various trucking companies. The lead agency for the partnership is the Kentucky Transportation Cabinet. The University of Kentucky's Transportation Center provides project staff and manages the operations center. The system design was performed by JHK & Associates. Science Applications International Corporation (SAIC) is the System Manager.



Hughes Transportation Management Systems (HTMS) is providing the Automatic Vehicle Identification technology, and the Iowa Transportation Center is serving as the independent project evaluator.

The project currently being conducted by the Advantage I-75 partnership is an operational test of MACS. The objective of MACS is to allow transponder-equipped and properly documented trucks to travel any segment along the entire length of I-75 (and Highway 401 in Canada) with no more than a single stop at an inspection station.

How Does MACS Work?

MACS is based on the use of Automatic Vehicle Identification (AVI) technology to electronically identify and process a truck while it is on the mainline. The AVI subsystem consists of truck-mounted transponders and roadside readers. Each participating truck has a transponder (installed in the cab) that is capable of two-way communication with the roadside readers. Each weigh station has a reader installed about 0.8 km in advance of the station, and an additional two or three readers in the weigh station complex (depending on the weigh station configuration). The transponders and readers communicate with each other via radio frequency transmissions in the 915-megahertz band, using a time division multiple access (TDMA) protocol, also referred to as "slotted aloha." The protocol has been placed in the public domain.

The basic operation of MACS is simple. When a truck begins a trip on the I-75 corridor and is processed through a weigh station, specific information about the truck and the transaction (e.g., date, time, location, weight data, axle data) is collected and stored electronically in the truck's transponder. As the truck continues its trip and approaches a subsequent weigh station, the information in the transponder is read by the roadside reader in advance of the station. The reader's computer processes the information, makes a clearance decision, and communicates this decision to the transponder. The transponder has built -in communication functions (red and green lights and audible tones) that signal the driver to either bypass or pull in.

One enhancement to the basic concept that is already being implemented is the use of high-speed, weigh-in-motion (WIM) equipment on the I-75 mainline. When a truck begins a trip on I-75 and the first weigh station encountered has mainline WIM, even the first weigh station stop can be eliminated.

MACS is being installed at every weigh station on the I75/Highway 401 corridor from Miami, Fla., to Belleville, Ontario. This is a total of 30 weigh stations; 22 in the United States and eight in Ontario.

Each weigh station has a host computer that controls the system and provides an interface to the system for enforcement personnel. Another computer, located at the project's operations center at the University of Kentucky, provides a central location for the enrollment of carriers, system monitoring and diagnostics, data collection, and report generation. The operations center also provides a help desk and a toll -free hotline for project partners.



The project has purchased 4,500 transponders for installation onparticipating trucks.It is likely that the demand for the transponders will exceed 4,500; if so, to enrolladditional trucks, the trucking companies must pay the cost of the additional transponders$75 per truck. Project officials expect that the number of participating trucks willcontinue to grow throughout the two-year operational test.

Costs and Benefits

The total, cumulative, public-sector cost of the Advantage I-75 operationaltest project from 1990 to 1997 will be about $12 million. Approximately 80 percentof this funding is being provided by the federal government; the balance is comingfrom the Advantage I-75 states and province.

During the operational test, a significant amount of effort will be directed towardsystem evaluation. A major focus of the evaluation will be to identify and quantifythe benefits of the system.

The primary benefit of MACS is expected to be increased productivity for trucking.A reduction in the amount of time spent waiting for processing at weigh stations willtranslate directly into cost savings; increased productivity; and more reliable, ontimedelivery of goods. Increased trucking productivity will, in turn, reduce transportationcosts and thus reduce the costs of goods for the consumer. In addition, reducing thenumber of times a truck must decelerate and accelerate, as well as reducing idlingtime, will result in improved fuel economy and reduced exhaust emissions.

The enforcement community should also benefit from Advantage I75. By allowingthose carriers with the best safety and compliance records to bypass weigh stationson the mainline, enforcement personnel will be able to concentrate their efforts onthe more problematic carriers.


A bending-plate weigh-in-motion system is used in Scott County, Ky., to weigh trucks on the I-75 mainline.


By eliminating repeated checking of the same vehicle, we will improve enforcement efficiency, allowing more effective allocation of scarce resources.

The data collected by MACS also has significant value. Every transaction between a roadside reader and a transponder is logged in the weigh station host computer and periodically uploaded to the central computer at the operations center. Information of this type is of great value to trucking companies, shippers, or customers who wish to track their shipments. Enforcement agencies will also have access to valuable data on motor carrier operations within their respective jurisdictions.

Of course, the benefits described here represent only the tip of the iceberg compared to the potential benefits if the Advantage I-75 concept is expanded and enhanced. Once the MACS system is in place and operating, there are numerous enhancements that can be added, and there are many ways in which the system can grow.

Enhancements and Growth Directions

One of the simplest ways in which Advantage I-75 can grow is in the number of participating trucks. The initial enrollment of 4,500 trucks represents only a small percentage of the total number of trucks that travel in the I-75 corridor. As the project progresses, it is reasonable to expect that additional trucking companies will express interest in participating. The cost of a transponder can be recovered very quickly when weigh station stops are being eliminated. Of course, acceptance into the project will require an acceptable safety rating, safety record, and vehicle inspection program. This will provide an incentive for carriers who do not meet the criteria to voluntarily improve their safety performance to qualify for the bypass privilege.

Another way for the project to grow is geographically. While Advantage I-75 is a corridor project, I-75 intersects many interstate highways to which the system could easily expand. Several states have already expressed interest in expanding MACS to additional interstate highways. The current system has been designed to support a network of highways, rather than just a corridor, so MACS can readily develop into a regional or even national system of commercial vehicle electronic clearance.

There are also many potential system enhancements that have been recognized. Two of these have been already mentioned: (1) incorporating mainline WIM equipment into the system and (2) providing vehicle location and tracking data to trucking companies, shippers, and customers. Others include:

  • Providing traveler information and safety advisories to transponder-equipped vehicles. The Advantage I-75 transponder has an interface that can be connected to other onboard devices, such as an onboard computer or display device. When connected, the transponder can receive messages from the roadside and display them for the driver.
  • Providing an automated, multistate permit-issuing capability. The partnerships, databases, and communications infrastructure established for Advantage I-75 can be used to support automated issuing and monitoring of permits for travel anywhere on the Advantage I-75 corridor. This capability could include oversize/overweight permits or any other type of temporary operating permit.
  • Improving incident detection using Advantage I-75 vehicles as probes. The ability to detect transponder-equipped vehicles as they pass selected points makes them ideal to serve as probes to determine travel times and detect incidents or congestion.
  • Monitoring safety. As devices are developed that can continuously monitor various safety parameters of the vehicle and the driver, the Advantage I-75 transponder can be used to communicate this information to the roadside for use by enforcement agencies.
  • Collecting tax data. Collection of data on kilometers traveled for use in allocating fuel tax could be greatly improved and automated, thus improving data accuracy. This could reduce the administrative burden on trucking companies and state agencies and could result in a more equitable assessment of taxes.
  • Tracking the movement of hazardous materials (HAZMAT) and responding to incidents. The movement of HAZMAT could be tracked by equipping trucks with Advantage I-75 transponders. Response to HAZMAT incidents could be enhanced by providing truck-specific cargo information and response guidelines in the MACS database.


The Advantage I-75 venture has, from its beginnings, been directed toward providing an early success story in ITS. The motor carrier project has intentionally been focused on a specific, achievable objective with a system design that allows incremental expansion. Advantage I-75 provides an example of how ITS technologies can be applied now, at moderate cost, to achieve tangible benefits, while also allowing for expansion and enhancements as new technologies and applications are developed.

When the ribbon is cut for Advantage I-75 this autumn, it marks the beginning of the operational test project. However, it also serves as a tribute to the strength of the Advantage I-75 partnership. Throughout the development of the system, there have been issues and potential barriers that could easily have derailed the project. The trust, cooperation, and tireless effort of the project partners allowed those issues to be resolved. Much work still must be done. The system needs to be operated, maintained, evaluated, refined, enhanced, and expanded. Nevertheless, the project partners should be justifiably proud of what has been accomplished. The project has moved from concept to reality.

Managers of the project are excited about the next two years. If, as we expect, the system provides tangible benefits for both the trucking and enforcement communities, then the Advantage I-75 will continue to grow through expansion of the system to other corridors and through enrollment of additional trucking partners.

Joe Crabtree is the director of the Advantage I-75 Operations Center at the University of Kentucky's Transportation Center. He also manages the research activities of the Transportation Center in the area of policy and impact analysis, and he serves as an adjunct professor of civil engineering.

He has seven years of transportation research experience, four years in manufacturing management with Mobil Chemical Company, and four years as a nuclear propulsion officer in the U.S. Navy. He received his bachelor's and master's degrees in civil engineering from the University of Kentucky.