They said the number of drivers caught speeding had risen from 4,000 in 1999 to more than 17,000 in three months this year.
Strathclyde Police is one of eight British forces which acted on a Department of Transport initiative allowing them to put all of the money raised from speeding fines back into maintenance of cameras.
Northamptonshire Police have revealed that the use of all the money which would normally have gone to the Treasury has led to a sharp increase in speeding convictions.
They said the number of drivers caught speeding had risen from 4,000 in 1999 to more than 17,000 in three months this year.
Details of the scheme's success came as the first digital speed cameras - capable of photographing three vehicles a second - went into operation.
The cameras have been mounted on distinctive blue posts and track the average speeds of cars travelling between two cameras.
Nottingham became the first city in the world to install the cameras on a permanent basis. They do not require any film and are very cheap to maintain.
The cameras track vehicles' average speed and then send a photograph of the offending cars to a police computer.
They can photograph the number plate of the vehicle, electronically check who owns it, and send out the penalty notice.
Reduce casualties
Other forces in the cash for cameras scheme have reported similar successes to Northamptonshire.
South Wales Police said the number of speeding tickets had doubled. Cleveland and Thames Valley police also reported increases.
Jacqui Elliott of the cameras' manufacturer, Speed Check, said the aim was to reduce casualties by one third over the two-year scheme.
"That means over 78 serious accidents could be avoided, 12 of which could have been fatalities.
"Motorists may need to change their driving behaviour to drive within the speed limit for the whole stretch of road."