Gay Byrne was speaking after reports that authorities in Britain plan to introduce 20mph (32kp/h) limits in residential areas, in an effort to reduce road deaths.
Speaking on RTÉ's Marian Finucane Show, Mr Byrne said he believed most people were making an effort to improve their behaviour on the roads but some drivers would always ignore all warnings.
He said the introduction of speed cameras was the only way to catch motorists who insisted on breaking speed limits, in the same way as an increased number of checkpoints has helped detect those who drive over the legal alcohol limit.
