Existing vehicle data bus, cellphone SMS proposed for nearterm VMT charge

July 10, 2009
By Peter Samuel

Engineers at the University of Minnesota (UMinn) have devised a plug-in device for measuring vehicle-miles traveled and logging it for road use charges (RUC) that they say could be deployed near-term. The system makes use of an electronic processor and memory that can be plugged into an existing vehicle data bus via a Data Link Connector plug, and which uses cellphone data links. The data link connector at the heart of the UMinn proposal is already installed in all vehicles manufactured in North America since 1996. Its primary purpose is for engine diagnostics at repair garages and emission control monitoring.

The UMinn RUC device uses cellular telephone location finding to establish general location and uses cellular telephone based wireless text messaging for automated uploads of charges incurred, and credits due to the various authorities levying RUCs.

No new infrastructure needed

A big selling point for the UMinn RUC device is that no new wireless infrastructure is needed, no roadside readers.

The device has no directional antenna of the kind used in a regular electronic toll transponder, just a cellphone modem. It can therefore be buried under the dashboard in the space above the driver's knees, rather than being on the windshield.

Data link connector means it is plug & play

With most vehicles already equipped with the needed data link connector plug, and making use of the existing cellphone infrastructure UMinn RUC devices could be in use nationwide within a couple of years.

The basic UMinn plug-in RUC device is designed primarily to measure distance traveled since the highest priority is seen by the authors as being a charge that replaces the gasoline/diesel fuel tax as the primary funding for roads.

The RUC device's cellphone tower based location finding would be sufficient to locate each vehicle by general area. Where greater location detail was needed the system could be enhanced with cellphone frequency beacons. That would allow pricing by individual roadways, the authors say.

Avoids problems of GPS

The UMinn RUC proposal challenges a widespread notion that GPS or satellite location finding in-vehicle devices are needed for wide area road use charges.

GPS works most poorly where RUC needs good location finding most - in dense urban environments.

The cellphone-based RUC would have an advantage over GPS units in dense city environments and under bridges and in tunnels where GPS signals are distorted or completely blocked, but where there is usually a dense cellphone infrastructure. Most GPS proposals involve log-ins and uploads of travel data at gasoline stations, and therefore they won't work for all-electric vehicles.

For the VMT uploads to the billing office the UMinn RUC proposal uses SMS/text messaging, now generally available in the US via cellphone networks. It is not dependent on gasoline stations.

The proposal is laid out in a report titled "Technology Enabling Near Term Nationwide Implementation of Distance Based Road User Fees" is authored by Max Donath, Alec Gorjestani, Craig Shankwitz, Richard Hoglund, Eddie Arpin, PiMing Cheng, Arvind Menon, and Bryan Newstrom of the Intelligent Transportation Systems Institute, University of Minnesota, Minneapolis. We'll call it the Near term road use fees report or UMinn report or the Donath report.

The full report is available here:


The UMinn RUC would plug in to the OBD2's Data Link Connector. All motor vehicles manufactured since 1996 come with an OBD2 mounted in the dash under the steering column. It provides garage mechanics with access to vehicle data for engine diagnostic work and has data useful  for emissions control  monitoring.

The UMinn device would plug into this data bus and read the vehicle speed, draw on an electronic clock signal, and calculate distance traveled.  It would use cellphone tower identification to tag the data with a location.

Vehicles manufactured after 2002 also provide a reading of the VIN (vehicle identification number) via the OBD2.

Some insurance companies have already made use of the OBD2 connector, inserting a memory module and using the data to calibrate insurance rates according to distance traveled and speeds driven.  The UMinn RUC module would be similarly placed and would also have a female connector for the bus original purpose at the garage, or for an insuran \ce company device.

The UMinn RUC plug-in would time and location stamp data on vehicle movement, and the VIN, encrypt it and transmit to the RUC office via automatic cellphone text messaging. The uploads could be timed off-peak to occur when normal text messaging volumes were slight. Private vehicles would upload VMT data at least weekly, commercial vehicles daily.

"The device mounted on the OBD2 Data Link Connector is designed so that a second OBD2 DLC on the device is accessible by shop personnel, so that its original functionality (vehicle diagnostics) remains intact. The device would come in multiple configurations so that the open connector is not blocked by adjacent vehicle structures, which vary from vehicle model to model. Sufficient electronic memory would be included to store the last VMT data set that was transmitted AND a data set that is being computed.

"One VMT data set is always retained until a new one has been calculated and transmitted. The memory must be such that it retains its data without power. To enhance privacy, no archive (other than the last VMT data set) would be maintained once the data are transmitted. If auditing is desired, additional memory can be included to maintain an archive exclusively for this purpose.

"If additional privacy is desired, the state and federal VMT rates for that vehicle year and model can be set on the device when initialized on startup (and updated at appropriate intervals). These would then be used to compute the state and federal road user fees. The VIN, the computed fees,
and the time stamp (i.e., the VMT fee data set, rather than the VMT data set) are then combined in an appropriate format, encrypted, and transmitted to the back office....

"A recommended scenario is that the device be installed by one’s local “certified” service station (to ensure correct installation), which would send the VIN and corresponding vehicle odometer reading at the time of the installation to the appropriate agency or back office. When first turned on, the device would electronically acquire the actual time and send off its first VMT data set (with a zero VMT), equivalent to its initial odometer reading."

Donath and coauthors go into some detail describing how the motorist could check the VMT data set for accuracy by calling or logging in with the a personal ID number.

The system  provides for various payment methods including bill-by-mail, credit accounts, online payment, payment at a gasoline pump as in the Oregon demonstration. It has a scheme for providing a credit for gasoline/diesel tax paid against the RUC.

Text messaging would be via new cellphone area codes, about 30 new ones providing for 300m vehicles at 10m vehicles/area code.

"To facilitate enhanced security, the device would be programmed with a preset list of addresses/phone numbers. These are the only destinations to which it will be able to transmit a VMT data set. Similarly, the device would be programmed with a separate preset list of addresses/phone numbers, the only addresses from which it will accept requests for a VMT data set.... (S)ecure encryption algorithms, which have been developed for payment and commerce applications, can also be applied here."

Location finding

The UMinn RUC device is constantly locating the vehicle using its cellphone modem to read the identifier numbers of nearby cellphone antenna towers.

"(A) device-resident database associates all towers in each identified travel zone with a common tag. The onboard database contains no longitude or latitude data, just tags representing each zone, or zone classification. The accuracy of such a system to identify the zone of travel would certainly be sufficient for recognizing travel within a state and would also be more than adequate to distinguish travel within different counties."


The UMinn proposal is that enforcement would be associated with a tamper-proof seal and involve an annual inspection by a certified agent, and automated random checks of VMT data uploads.

Enhancements with RFID transponder-reader systems

Donath and coauthors describe a set-up in which regular windshield or license plate-mounted RFID transponders could support their datalink/cellular device. They see various kinds of RFID/UMinnRUC collaboration to:

- check on the accuracy and calibrate the UMinnRUC device RFID readers could be set a known distance apart, triggering the check and allowing data to be corrected

- check the presence and functioning of the RUC device RFID could be checked, supplemented with license plate readers

- reconcile tolls on tollroads with the VM or RUC fees

- add congestion pricing in certain areas

- allowing in-vehicle display of congestion information and pricing options 

- collaborating with Nationwide Differential GPD in areas where it operates

They summarize the advantages as being independent of GPS and thus can:

- work in all environments (including tunnels, skyscraper canyons, etc.),

-  maintain the vehicle’s privacy since no location is ever captured or saved on the device

- be installed with little effort as a plug-in, requiring minimal skill and no wire harnessing

- requires no new deployment of infrastructure except as described for automated enforcement and VMT
‘surcharges’ for specialized facilities

- allows for varying the ‘rate’ based on the fuel efficiency and the carbon footprint for that vehicle year and model contained in the VIN data

- allows for plug-in hybrids and electric vehicles to pay their fair share for road use

- be used for trucks with provision made to capture data for the towed trailer on combination trucks, a time stamp indicating when trailer is
hitched and unhitched, number of axles on trailer, gross vehicle weight etc

GPS devices by contrast require:

- mounting for an antenna with a line of sight to the sky

- power connection

- digital maps and map matching

The report lays out the detailed tasks needed to be performed by the microprocessor in the schematic form needed by chip designers and for programmers writing the code.

COMMENT: This seems to be an important concept that has considerable credibility as a first generation technology for nationwide road use charging.

A critical issue will be the accuracy of the distance measurements computed from the data bus, and the extent to which recalibrations are needed. Our guess is that the enhancements with RFID will be essential.

Another issue will be the cost of these devices. They require a processor and memory beyond that on most existing electronic toll transponders, also a cellphone chipset, plugs and wiring. Hopefully under $50 each by the million.

The concept is brilliant in that it piggybacks on an existing cellphone network and has a plug-&-play simplicity by using the data link connectors under the dash in 90% or so of the vehicle fleet.

TERMINOLOGY: By RUC we mean Road Use (not 'useR') Charge. Road Use Charge is the correct term, because what is being charged is use of the road. Road UseR Charges by contrast are charges on road users and therefore encompass vehicle registration fees, driver license fees, sales taxes on cars, taxes on fuel, and any other kind of tax or charge on the user of the road.

TOLLROADSnews 2009-07-09 ADDITION 2009-07-10 12:00

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