Trials have begun of a new electronic tolling system on the Tamar Bridge and Torpoint Ferry crossings between Devon and Cornwall.
The Tamar Bridge carries about 50,000 vehicles a day
The system, which involves having tags on windscreens, will mean regular drivers using the routes are charged automatically as they cross.
About 500 people are involved in the trial of the new TamarTag system.
The tag scheme is replacing the 15-year-old system of discount vouchers for frequent users.
Roadside equipment will detect the tags and trigger a debit from a pre-paid account.
The trials are just being carried out on one lane of the bridge and on one ferry.
The Tamar Bridge, which opened in 1961, carries about 50,000 vehicles a day alone.