Almost 1,000 motorists have escaped speeding fines in Northern Ireland in the past year.
A backlog in the processing centre meant some fines were not processed within the legal timeframe, police have said.
Fines are processed by staff from the security firm G4S.
The Police Service of Northern Ireland (PSNI) said a shortage of staff was one of a number of factors to blame for the failings.
In the past 12 months, 939 detections had been cancelled from approximately 46,000 detections, as they were unable to be processed within the specified six-month timeframe, the head of the PSNI's operational support department told the Nolan Show.
"This issue relates to detections made by the mobile safety camera vans and fixed cameras," said T/ACC Jonathan Roberts.
Police said they became aware of the backlog in September, but that a "collaborative plan" had been developed with G4S - an outsourcing firm which provides staff to process speeding fines for police in Northern Ireland.
Most of those within the 939 cancelled fines relate to people who failed to comply.
ACC Roberts said the people who failed to comply were people who "have not accepted penalty points, paid their fine or have not accepted the offer of attending a speed awareness course".
Leading road traffic and criminal defence lawyer Nick Freeman said it was possible if those who had not been fined had gone to trial they would have been acquitted.
However, he said this did not give people who "accepted their responsibility" any right of action.
Ulster Unionist assembly member Mike Nesbitt, who sits on the Policing Board, raised questions about the contract in place between the PSNI and G4S and whether the contract put any responsibility on them in terms of the financial loss.
"At 939, you're talking a minimum of £56,000 if it's a £60 fine. If it's a £200 fine you're way into six figures. That should not rest with the public purse," he said.
In a statement, the PSNI said: "As we work to resolve this issue we can reassure the public that road safety and addressing speeding concerns remains a priority.
"Our road safety vans will continue to be deployed and police officers will remain on the road network 365 days of the year preventing and detecting speeding and other motoring offences."
G4S referred the BBC to the police statement.