On Tue, Aug 26, 2008 at 11:56 AM, Dustin D. Trammell
> This is the same for the state-wide Texas tag, TxTag[1].  If your tag
> doesn't register, or you disable or remove it, the toll system can still
> accurately bill you based on your license plate and vehicle
> registration.  If you're not in the TxTag system at all, they simply
> mail you a bill.

I think this is a bit different than what Michael Heyman said.  TxTag,
IIRC, was implemented by the same company (Raytheon) that implemented
the 407 ETR toll system in Toronto.  In the case of the 407, there is
no image recognition done if the car has a valid transponder.  Only in
the case of a missing or invalid transponder is the plate imagery
used.  Supposedly the OCR has a high enough error rate that there is
still manual verification of plates before sending a bill, and
accordingly a $3.60 additional charge is applied per trip.

If the images are used even when the vehicle has a valid transponder
-- as Michael Heyman suggests is happening with E-ZPass -- then it
might be feasible to have back end defenses against cloning, though
not without inconvenience to customers who borrow cars, buy new cars,
or rent cars while their own is getting serviced.  Also as Matt Blaze
pointed out this makes the transponder wholly redundant.


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