Final answer:
Double yellow lines are used to mark the center of a roadway with four or more lanes of traffic. Vehicles cannot cross these lines to pass, but they can cross them to make a turn.
Step-by-step explanation:
The yellow lines used to mark the center of a roadway with four or more lanes of traffic are called double yellow lines. These lines indicate that vehicles are not allowed to cross them to pass other vehicles. However, vehicles may cross these lines to make a turn when it is safe to do so.