To use the system, drivers must place the Tag transponder on their windscreen to identify their vehicle as they drive through the toll lane.
Lanes through the toll booths are dedicated as either Tag (unstaffed), cash (staffed) or automatic debit/credit card only.
This was judged a misuse which can result in a Severn River Crossing "Fine" of £25+VAT.
[4] Whereupon the reader would issue the message "Tag Error" the barrier remains closed and the lane is then blocked.
In July 2017 it was announced that all tolls on the bridge would be abolished,[8] and they were discontinued on 17 December 2018.