Neil Greig, from the Institute of Advanced Motorists, said a successful bus lane should not make any cash from fines.
But the £2.5million collected in 2013, from more than 100,000 penalties issued in Glasgow, raises concerns about the project in the city, he said.
Mr Greig, who is the director of policy and research from IAM, told the Evening Times: "The measure of a successful bus lane is not how much money it brings in.
"I would suggest if a lane is raking in thousands of pounds every year it needs to be reviewed. There is likely to be an issue with signage or markings.
"An ideal lane would not catch anybody."
There are 173 bus lanes across the city of varying lengths but only 15 are enforced by cameras which record the registrations of private vehicles prohibited from driving in the lanes and fines of £30, increasing to £60 if not paid within 14 days, are issued.
Cameras were fitted on nine of the lanes in April 2012, one in February 2013, and a further five in November and December 2013.
A camera in Cathedral Street was removed in March last year after part of the road was closed to traffic.
We told you yesterday how Glassford Street was the biggest-earning bus lane for the council generating £545,280 in 2013.
Mr Greig added that while there has been a slight downward turn in the number of drivers caught out, there are still issues about this particular lane.
He said: "Glassford Street is well known as the lane where most drivers have been caught.
"But in this case there is a concern here about access to a NCP car park.
"If a bus lane is pulling in a lot of money it needs to be reviewed frequently."
The motoring expert said that there has been little in the way of evidence from Glasgow City Council to convince the general public of the success of the lanes.
Mr Greig said: "It is very difficult to point to any improvements that have come out of this like fewer potholes, better roads infrastructure or new parking meters.
"If the council really wants to sell this to us it needs to point to something specific.
"The only measures of success seem to be the number of fines issued, not statistics on the number of people leaving the car at home."
Glasgow City Council says the money made from fines - more than £2m last year when the £437,453 cost of administering the penalties is deducted - is spent on "transport strategies".
Mr Greig said that the council must not bank on this money to carry out improvements.
He said: "Over the last few years a lot of money has been made.
"I am concerned that the council may start to rely on this £2m a year to prop up the transport budget, that cuts could be made elsewhere if there is a dependency on this money."
He added that Glasgow's bus lane scheme, in comparison to a similar project in Edinburgh, was initially managed better.
But said motorists are getting fed up: "In Edinburgh there were fines being wrongly issued, people fined for coming out of their driveways etc.
"There hasn't been quite as much anti-camera favour in Glasgow.
"But I think that as time has gone on, more and more people have seen this as a money earner and not a way to get more people taking the bus."
Glasgow City Council says that the number of drivers illegally driving in Glasgow's bus lanes has more than halved in the last 12 months.
Bus lanes were first introduced in the city as part of "route action plan corridors" in 1997/98.
These corridors were along Maryhill Road/Queen Margaret Drive, Thornliebank Road, Pollokshaws Road, Eglinton Street, Victoria Road and Gorbals Street and they were all 24-hour operation.
There are now 173 individual bus lanes of varying lengths throughout the city, of which 81 are peak period only and 92 are 24-hour operation.
The council, as the roads authority, ultimately decides where bus lanes are placed. This is done with support from SPT who consult with bus companies, they say.
All decisions are passed by a committee.
The council says the main purpose of a lane is to: improve bus journey times and reliability; make bus travel more attractive; encourage more people not to travel by car; and reduce air pollution.
A spokesman for the council said: "Buses are the most frequently used public transport option for local journeys in the greater Glasgow area.
"Less than half of Glasgow households have a car."
An "independent evaluation" of bus lanes has been undertaken, says the council, to make sure the lanes are in the correct places and that they are effective in terms of reducing bus delays, improving journey times and increasing passenger numbers.
A council spokesman added that "civil enforcement" bus lane cameras are helping to lower the number of offences also "improving the flow of traffic on a number of congested stretches and improving the reliability of bus journeys on some key routes".
He said: "Around £30m was invested by the council, First Glasgow and the Scottish Government, in a bid to improve public transport in the city and the bus lane enforcement scheme is helping to get full benefit from that.
"It is important we work to ensure public transport services are given priority and this is respected by the majority of drivers. There are very clear and constant reminders of the law - signage and the bus lane markings on the road.
"Regrettably, some selfish drivers continue to break the law, and as with many other driving offences, camera enforcement is an effective deterrent."