If by Level of road deaths you mean the rate of road deaths then it appears that you may be correct, in the 1970's the average no of deaths was 378. For the last nine years it has been 412 (a total incerease of 8%) I can't find the number of cars on Irish roads in the 70's compared to today but it's a safe bet it has more than doubled -googlers to your positions please. If these assumptions are corrct then the rate has about halved.
Broughahaha: didn't see UR last post before I posted mine, but it looks like the same conclusion