The introduction of the new metric speed limits at midnight last night was accompanied by complaints that the opportunity to review certain speed limits had been missed.
The criticisms centred around inappropriate speed limits which, it has emerged, cannot be changed until guidelines are finalised and issued by the Department of the Environment.
A range of inappropriate speed limits were identified more than two years ago by the Minister for Transport, Mr Brennan.
The Department wrote to local authorities as far back as 2003 and again in 2004, asking them them to review their speed limits.
While the local authorities were praised by the Minister of State at the Department of Transport, Mr Ivor Callely, for efforts in erecting almost 60,000 new speed limit signs, he said some had failed over the last 11 years to put appropriate speed limits - particularly in relation to those outside schools - in place.
Where limits outside schools on national routes have not been changed by local authorities, the official limit yesterday was 60 m.p.h. and is today 100km/h. Where the local authorities have failed to change them outside schools on regional roads, the limit is now 80km/h. In towns, speed limits past schools have increased marginally from 30 m.p.h. to 50km/h.
The Irish National Teachers' Organisation (INTO) claimed that "lives will be in danger because of the limits", and described the change-over as a "golden opportunity which has been missed".
Agreeing with the INTO, the Automobile Association described the changeover as a "missed opportunity" for a general review.
The AA said inappropriate speed limits - both too high as well as too low - brought the whole process into disrepute, with ongoing safety implications.
According to the AA spokesman, Mr Conor Faughnan, speed limits which had been as low as 30 m.p.h. on the State's newest triple carriageways at Loughlinstown, Belfield and Lucan in Co Dublin were "derisory".
Mr Faughnan said that the 40 m.p.h. limits at Lucan and Belfield should have been revised before being automatically reduced to 60km/h. The 30 m.p.h. limit at Loughlinstown had been "simply ludicrous", he said.
"It just makes people concentrate on not getting caught and demeans the whole process. Local authorities dropped the ball here," he added.
In a separate issue, the Garda acknowledged that not all its speed cameras would be changed over to kilometres by today and some Garda fines books continue to record speeds only in miles per hour.
The Garda said, however, it was "satisfied" it had enough machines to handle the change-over.
The National Safety Council also defended the change-over, commenting that "the most significant change to speed limits in the history of the State" was being achieved and "would improve safety".
