More than 10,000 fines have been issued to drivers using bus lanes in Leicester in just two months.
Camera monitored zones were introduced in Charles Street and Causeway Lane in July with fines ranging from £30 to £90, depending how quickly people paid.
City council figures showed 6,049 fines were imposed in the first month and 4,365 in August.
Officials said the routes were clearly signposted and there was no excuse for unauthorised vehicles using them.
The council insisted the scheme was designed to cut congestion rather than make money.
Director of Planning, Transportation and Economic Development, Andrew Smith, said: "We have made it very clear through signage and consultation before we introduced the bus lane enforcement scheme.
"But people still continue to enter the zones and while they do that they will incur a penalty."
Mr Smith added the money would be invested in transport infrastructure and more routes may become camera monitored.