Rush-hour motorists in Cardiff are spending more than half their time stationary during their morning commute to work, a survey has revealed.
St Mary Street is one of the busiest roads in Cardiff city centre
Of six cities studied by Citroen, including London, Cardiff jams were worst, with drivers spending more than 30 minutes at a standstill in an hour.
But Cardiff drivers were able to cover more miles than Londoners in that time.
Friends of the Earth Cymru called for drivers to leave their cars at home to ease congestion and save money.
The Citroen survey found that typical Cardiff drivers were able to complete 15.7 miles during a one-hour morning commute.
In contrast, London drivers were able to cover only 6.8 miles in an hour but were stationary for just over 19 minutes.
The best commuting conditions were found in Edinburgh where drivers were able to cover 17.3 miles in an hour and were stationary for just under 18 minutes.
Whether motorists are driving a small or larger vehicle, they will ultimately feel the delays in their wallets, says the AA.
It estimates that a small car loses 1.5p per minute of petrol every time it stops. This figure rises to 3p per minute in a medium car.
"This means Cardiff motorists in medium-sized cars with an hour-long commute are losing about 90p each time they get stuck in congestion, according to these figures," said the AA.
Time stationary in 1 hour commute
London: 19m 20s
Cardiff: 30m 13s
Norwich: 20m 32s
Birmingham: 21m 44s
Edinburgh: 17m 54s
"And assuming there are similar delays on their way home too, that pushes the figure up more than, say, £1.50 per day."
With these estimates, motorists could be losing up to £390 per year due to traffic jams, says the AA.
"It is a pretty hefty total and this can only be bad news for the businesses and the economy," said the spokesman.
Miles covered in one-hour commute
"The only way to alleviate these findings is to find an alternative way to work or find a way of not driving in during the rush-hour.
"But many commuters have no alternative other than using their cars because the public transport system is not sufficient to meet their lifestyle needs.
"From a motorist's point of view it is extremely galling to use petrol and spend money while you are sitting in a traffic jam."
Friends of the Earth Cymru say drivers should leave their cars at home to ease congestion, cut costs and improve the city's environment.
A spokeswoman for the organisation said traffic queues and congestion created an "enormous amount" of climate changing carbon dioxide emissions.
"They also contribute to a poor quality of life," she said.
Cardiff councillor Elgan Morgan, executive member for environment and transport, said the council was trying to tackle the congestion issue by encouraging people to cycle, walk and use public transport.
New park and ride sites in the city's suburbs of Llanrumney and Coryton are being developed and the council was working with Cardiff Bus to improve routes and reduce bus journey times, he said.
"However, the amount of time spent stationary is perhaps not as significant as the amount of miles people manage to travel in total, which in Cardiff's case is not really different to any other major city outside of London in the survey," he said.