Almost £1.3 million will be repaid to motorists who were given an invalid fine for driving in bus lanes.
The Traffic Penalty Tribunal, which decides on appeals made by drivers against parking penalties, discovered that a sign warning of the bus lane restrictions was confusing for road users. It also found that the sign had been placed illegally, meaning the charges handed out were void.
The ruling means that Hertfordshire Council must pay back the fines it sent to drivers who were supposedly in breach of the rules.
The penalty notices had been sent to an estimated 34,000 drivers, of which more than 30,000 have already paid the fine.
While the road users involved did not technically break the law, other drivers who do could incur fines, as well as penalty points which could affectcar insurance premiums.
The council said it will get in touch with the motorists who were given penalties, but any unclaimed repayments will be donated to charity and any outstanding fines are not expected to be paid.
Copyright Press Association 2012