When vehicles enter the cross-over area, unless markings on the ground indicate two turning lanes in the cross-over, drivers form one lane. A cross-over with two lanes is designed at high-volume cross-overs, or when the right lane turns onto an intersecting street. In this case, the right lane is reserved for vehicles completing the design. Most crossovers must be made large enough for semi-trailer trucks to complete the crossover. This large cross-over area often leads to two vehicles incorrectly lining up at a single cross-over.