The arrangement, which came into effect on 20 January, took several million euros, involving the erection of 23,000 new road signs and replacing a further 35,000. Although the double switch resulted in little evident confusion, many say there are loose ends in the system which need to be tidied.
The Garda, the Irish police, warned that no special licence would be extended due to the changeover, with road users expected to familiarise themselves with the new system. An extensive advertising campaign set out the new speeds. The new system has four limits for different types of roads, which are shown on the new signs in terms of "km/h." From now on, the limits are set at 50, 80, 100 and 120 kilometres per hour.
The limit on motorways, which are regarded as the safest Irish roads, will increase from 70 to 75 miles per hour, that is 120 kilometres per hour. The current general limit of 60 mph, which applies to roads outside built-up areas other than motorways, is being replaced by two new speeds. That applying to rural national roads, which include most dual carriageways, will go up slightly from 60 mph to 100 km/h (62 mph). The most significant change is on rural regional and local roads, which the Irish often refer to as non-national roads, dropping from 60 mph to 80 km/h, the equivalent of 50 mph. This is a reduction of 20%.
These roads, which make up 90 per cent of the network, are often the scene of fatal accidents. The hope is that the speed reduction will lead to fewer deaths on what have been described as Ireland's most dangerous and poorly policed roads. Road deaths on the Irish Republic have been on the rise, going up from 336 in 2003 to 380 last year.
The fourth and final change applies to built-up areas in cities and towns, where the limit has gone up slightly, from 30 mph to 50 km/h (31 mph). One concern is that few cars on Irish roads have kilometres as the main measurement on their speedometers, a problem for which, the authorities say, there is no "one size fits all solution."
There is no scheme to retro-fit speedometers, they say, due to the sheer number of vehicles that would have to be changed and due to the fact that different models would require different speedometers.
Despite the attempts to achieve mathematical precision, anomalies will remain, partly because councils have a say in setting limits. One stretch of motorway close to Dublin, for example, will have a 100km/h limit rather than 120km/h, the local council ruling that the road was not built to motorway standards and was "constructed with 60mph curves."
According to Cyril McHugh, of the Society of the Irish Motor Industry: "The whole credibility of the country's speed limits is being put in jeopardy by limits that are totally inappropriate. Speed limits throughout Ireland need to be both sensible and logical and, most importantly, consistent."
Meanwhile the huge question remains: will Ireland's speeding young men, some of whom notoriously disregard motoring laws, pay more attention to the new system than they did to the old?