Returning home from IAD on the 12/9 (in heavy rain), I missed the entry to the Dulles Access Road and ended up on the toll road. The only sign I noticed read "To I-495." I don't remember seeing anything saying "Dulles Access Road (No Toll)" or "To I-66." Since I found myself in the wrong lane and didn't connect the "To I-495" sign to the Access Road, I didn't exit. Next thing I know, I see a sign telling me to pay toll ahead. Only then did everything click. Hopefully signage has improved since then, but now I'm definitely on the alert to take the left exit onto the access road upon exiting the airport.