I have worked in Sandyford on and off for years now.
In 2006/2007, the traffic was savage in rush hour. I wasn't in Sandyford for 18 months and when I went back working there in Nov 2008, I was pleased for myself and horrified for the economy how light the traffic was.
For the last 2 years, the traffic has got steadily worse out there, even though the Luas now goes to Central Park. Even the Luas is busier on the days I take it.
There are even far more cycling commuters on the roads, at least there are in good weather. ( Lots of shiny new Cycle-to-work scheme bikes)
This is a gradual increase over the two years, not seasonal variations.