During January 2005 Ireland converted its speed limits from MPH to KPH in a well planned operation that resulted in minimal confusion and disruption. Since then all cars sold in Ireland are equipped with speedometers that are measured in KPH. The speed limits were reduced on 91% of the roads during the change to metric in an aim to improve road safety. If you are planning to drive through Northern Ireland while in Ireland, please be aware that the speeds have not been converted to metric in Northern Ireland and are still in MPH.

Drivers should observe all posted speed limit and road signs. Weather conditions and the size and condition of the roads can vary widely. Therefore, common sense should be used while traveling. Note that road surveillance cameras strictly enforce speed limits. Any driver (including foreigners renting cars) photographed speeding will get a nasty bill in the mail. (Cameras flash on your rear license plate in order not to invade the privacy of anyone sharing the front seat with someone they shouldn't be with.)

National roads - Speed limit is 100 km/hr (62 miles/hr) - (roads on the map with an 'N' number and signs colored green).
Motorways - Speed limit is 120 km/hr (75 miles/hr) - (roads which bear an 'M' number and have signs colored blue).
Regional Roads - Speed limit is 80km/hr (50 miles/hr) - (signs are colored white).
Towns and Cities - Speed limit is 50 km/hr (30 miles/hr).
Special limits (Schools, etc) - 30 km/hr (19 miles/hr).

In Northern Ireland speeds are still measured in miles per hour with the standard speed limit set at 60 miles/hr.

If you are used to miles as opposed to kilometers, a very quick way to work out how far you have to go is take the kilometers, divide by eight and multiply by five, ie: sign says 32 kilometers, so divide by eight = 4, multiply by five = 20. You have 20 miles to go. It's a really simple way to work it out and you get used to doing it very quickly. Why not practice at home before coming over? Don't be too fussy with the mathematics - if the sign says 34km just round it off and allow for the slight difference.