Within the city center of Dublin, the default speed limit for roads is 31 mph. This limit remains the same for many of the roads within the city boundary. Be aware of speed cameras at either end of Dublin's Port Tunnel. If you’re traveling outside of the city on National Routes, the limit is 62 mph and on highways the speed limit increases to 75 mph. You will always be notified by sign posts where there is a change of speed limit. Search rental cars on KAYAK