Driving through a Toll on the highway?

Ok so I was driving on the highway and on the news i've been hearing about this new "zipcash" kind of thing where instead of paying at each toll you just go through and they bill you at the end of the month. Anyway, I was driving and was coming up to a toll, I thought it was zipcash or whatever its called and went through at a reduced speed, I realized that the light stayed red and there was people behind me so i couldnt reverse or anything so i kept going. No alarm went off but i'm worried whats going to happen, anyone know? please help, thanks