Public Transportation around IAD. HA HA
Sorry, no offense, but that is one thing that is sadly lacking. Most Pilots and FA's I know have crash pad cars. There are crash pads where a group of guys share a car as well as all sorts of other sharing arrangements. The only Mass transit is the Washington Flyer Bus to the West Falls church Metro Station. 25 minute ride at least and about $8.00, I think. Some people have crash pads at the Holiday Inn Express in Herndon which has a van service to and from the airport. Other people pay off the van drivers to hotel vans near their crash pads. Best bet is to get a car if you get based at IAD. As for ORD I have no Idea.
Welcome aboard!