In some cases, such as many areas in Illinois, the new Interstate Highway not only paralleled the old US 66, it actually used much of the same roadway. A typical approach was to build one new set of lanes, then move one direction of traffic to it, while retaining the original road for traffic flowing in the opposite direction. Then a second set of lanes for traffic flowing in the other direction would be constructed, finally followed by abandoning the other old set of lanes or converting them into a frontage road.