Figures obtained by the Otago Daily Times under the Official Information Act show almost $9.8 million in fines had been generated by speed cameras in the district during the past four years.
Fines totalled $2.9 million in 2007.
The total fell to $2.5 million in 2008 and further still to $1.9 million last year.
Southern district road policing manager Inspector Andrew Burns said it was likely the number of fines was declining because drivers were becoming more compliant.
"In general, we are not picking up such high speeds as we have in the past.
"It's a fact that seems to be in line with national trends.
"High visibility enforcement is also having an impact," he said.
Of the top 10 income-generating speed cameras in 2009 situated south of the Waitaki River, seven were in Dunedin.
The camera on Caversham Valley Rd, situated between Burnett St and Mornington Rd, topped the list for the past four years.
In 2008, it photographed 9368 speeding vehicles but only 3361 in 2009.
Insp Burns said the high number of vehicles photographed in Dunedin might not signify the city's drivers were defying speed limits - they could relate to the number of people travelling to and from the city, and that Dunedin roads were busier than others.
Clinton, Merton and Balclutha also had high volume routes, he said.
"Interestingly, in places like Auckland, the number of fines resulting from speed camera photos tends to be lower, because the traffic flow is more congested.
"There are high concentrations of traffic for short periods of time at lower speeds."
Road policing national manager Superintendent Paula Rose declined to give information about the fastest vehicle photographed by a speed camera in the district last year.
"The possibility exists that misguided people may try to break any maximum speed record that is published and any such publication may serve to either trivialise or sensationalise instances of serious offending."
Supt Rose said many vehicles caught by cameras in the region were snapped more than once.
However, speed camera notices were issued to the registered owner, and that person might not have been the driver at the time of the alleged offending, she said.
