WSDOT Toll Division has discovered an issue with toll tags of all types (sticker, license plate, motorcycle, and FlexPass) in which environmental factors cause bits in the tag memory to flip from zero to one or vice-versa. The result of this error is that the tag fails the validation check when lane-side equipment reads it. If this error occurs within certain areas of the tag memory, then the tag’s serial number may be affected, with the result that the transaction is applied to the wrong account. Preliminary investigations have shown that the error occurs in the serial number in approximately 0.15 percent of trips, meaning that 150 out of every 100,000 trips may potentially be assigned to the incorrect account. This research is collecting and analyzing tag data to determine the scope of the failed validation problems and to provide WSDOT Toll Division with recommendations for mitigation, including replacement of affected transponder tags. Because the analytical methods used to match failed tags are highly complex, the researchers will also clearly document the problem and the methods implemented to analyze the data.
Principal Investigator: Ryan Avery, Washington State Transportation Center, UW
Sponsor: WSDOT
WSDOT Technical Monitor: Michael Severance
WSDOT Project Manager: Doug Brodin
Scheduled completion: September 2024