Glasgow issued the lion’s share of penalty charge notices (PCNs) north of the Border, a Freedom of Information request revealed, with a total of 339,402 served from 2015-2017.
The city, which has 25 miles of bus lanes, reported the third highest total of PCNs in the UK behind London and Manchester.
Edinburgh, which has 40 miles of bus lanes, a total of 78,332 PCNs were issued in the same period - an average of 26,000 a year.
The RAC, which submitted the FOI requests to city councils across the UK, said it was concerned that drivers were being punished for accidently straying into bus lanes.
Of the 16 councils that provided full data, seven saw an increase in penalties handed out and nine saw a fall between 2015 and 2017.
RAC spokesman Simon Williams said: “Bus lanes have a vital role to play in ensuring the reliability of public transport as they help to keep our urban areas moving. But the sheer quantity of fines – more than a million every year – suggests something is awry and we don’t believe the vast majority are knowingly breaking the rules. While there is clearly no defence for deliberately driving in a bus lane, we believe more can be done to make it obvious to drivers when they can and can’t drive in one.
“A lot of this is down to improving signage. Every city driver will be familiar with the blue bus lane sign, but on city centre streets with a lot of signage ‘clutter’ it can be very easy to miss the specific times of operation. This poses the risk of drivers straying into bus lanes when they shouldn’t be or avoiding using one when they are actually allowed to.
“We also think it is time we saw modern technology being used to make things clearer for road users, which would also have the benefit of making the best use of available road space at times when bus lanes can be used by all vehicles. Stretches of smart motorway use roadside signs to indicate which lanes are open and closed – we believe towns and cities should now consider introducing ‘smart bus lanes’ that use similar signage.”