Cahill doubted that any of the tickets issued to officers travelling more than 50kmh over the limit were for non-emergencies.
There were 632 police vehicles caught speeding between January and September in 2015 - 475 of which were waived.
A police spokeswoman said police travel between 85 and 90 million kilometres every year, with more than 3000 vehicles on the road.
"Ideally, we'd like the number of infringements to be zero - however, given the high mileage travelled by police vehicles, how often we are on the road (24/7), and the size of the fleet it is going to happen from time to time.
"Policing is unique in that it requires officers to travel at higher speeds in some circumstances to respond to urgent situations. In cases where Police officers have a legitimate need to respond urgently, tickets are waived."
When officers are ticketed for speeding, it is followed up and an explanation is sought, the police spokeswoman said.
"If the speed is not found to be justified in the circumstances, the driver responsible is required to pay any infringements incurred."
"Where there are serious breaches of Police driving practice, officers may face a range of disciplinary actions. This for example may include retraining, suspension or downgrading of their driver status."
Police could not clarify whether the total amount owed in fines this year included the 541 tickets that were waived in 2016.
"Police are just as accountable for their driving as any member of the public, and we both demand and expect high standards. In any case where speed is not justified, we accept responsibility for this," the police spokeswoman said.
"We appreciate that we have a responsibility to model good driving behaviour and drive safely as we enforce the law for other motorists."