The gardai paid a speed-camera operator 14.6 million euro last year - but took in less than 7.2 million in fines as a result.
GoSafe has high-viz vans throughout the country, acting on the gardai's behalf to make roads safer.
They've been employed since 2010 to check drivers' speeds.
Sinn Féin's justice spokesman, Martin Kenny, says the contract is not good value for money.
