strangely enough I came across article yesterday (no idea now where it was) that estimated 17km to be the AVERAGE commute. I think it was a U.S., New York study so take it for what it is. I'd be interested in Ireland/Dublin figures.
Personally, I drive 60km to and from work (120 total per day).
As ever, 'average' is limited in what it tells us. Mode and median too would be more enlightening but there you go.
I had a quick look but couldn't see the info immediately. Blorg, however, replied with much more useful search results...quoted below.
Detailed travel data for the Greater Dublin Area (GDA)... http://dublinobserver.com/2011/03/dublin-data-blog-how-when-and-where-travel/
To put it in context: The GDA accounts for nearly 40% of the population of Ireland. Inside Co Dublin alone accounts for 30% of the population of the whole country in I think about 1% of the landmass, and the vast bulk of that again is inside the M50.