Re-read some of the info and everything says plates of " vehical " nothing about trailers. Here is a link to there site and a contact # you can call and ask for yourself. I-PASS Customer Call Center. 1-800-UC-IPASS. (1-800-824-7277) Weekdays: 6 a.m. - 10 p.m. Weekends: 8 a.m. - 5 p.m. More @Wikipedia
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