More than 9,000 motorists have been fined for using a bus-only junction since it opened, figures show.
The bridge over the M32 was constructed as part of Bristol's Metrobus project, which aims to shorten journey times in and out of the city.
Fines of up to £60 were sent out between 28 May and 26 August to drivers caught using the bridge on cameras at both ends of the crossing.
Bristol City Council said the bridge and approach roads were clearly marked.
Figures obtained through a Freedom of Information Act request revealed 9,458 letters were sent out, with 6,000 paid so far.
The majority of motorists were caught leaving the M32.
Bristol City Council said the bridge was a crucial element of the Metrobus route, helping to make it quicker and more reliable.
"Twenty-four-hour CCTV is in place along the bridge and we will issue penalty notices for up to £60 to anyone caught using this route without permission," a council spokesman said.
"If someone feels they have been fined incorrectly they can always appeal the decision."
There are two cameras - one to catch motorists coming off the M32 northbound, and another for those coming onto the M32 southbound.