Madness of differing speed limits

Dear sir - Since the opening of the M3 motorway on 4th June, the old N3 has now become the R147. One thing I cannot understand is the speed reduction from 100 km/hour to 80 km/hour. If it was safe to drive at the higher speed prior to 4th June, surely it is even safer now that there is considerably less traffic on the road. This madness is typical of the National Roads Authority. They reduced the limit on the N51 last year from 100km per hour to 80km per hour in County Meath, yet when you enter County Louth at Rossin it goes back up to 100 km per hour. The quality of the N51 in Louth is not as good as in Meath, yet one can travel at 20 km per hour faster in Louth. Yours, Liam Byrne, St Brigid's Villas, Navan.