The B8 highway is long. It contains the long Učka tunnel, the third longest tunnel in Croatia. The B9 highway is long. It includes the tolled Mirna bridge.
As of 2007, both expressways are completed in the two-lane freeway form. When the traffic levels reach 10,000 vehicles per day year-round or 16,000 vehicles per day during the summer, whichever happens first, the Phase II will start. It includes construction of the second roadway and an upgrade to a full-profile highway including changing the designations from B8 and B9 to A8 and A9, respectively. Current traffic levels are 600 vehicles per day at the Mirna bridge and 1,000 vehicles per day at the Učka tunnel.
Phase II involves converting the complete Istrian Y (except for some viaducts) to four-lane highway. Currently, only the southern arm (B9 south of Kanfanar) is four-lane. Upon finishing Phase II, a closed toll collection system will be in use. Only the Mirna bridge and Učka tunnel are currently tolled. Drivers driving at B8 or B9 at these places pay toll that amounts for the entire B8 or B9 length at the current highway toll tariff.