High-occupancy-vehicle (HOV) lanes in Phoenix were studied to see how well they work. The lanes help reduce traffic when the roads are busy. Cars in HOV lanes usually have more people in them than cars in regular lanes. This might be because people are choosing to carpool or use other ways of getting around. Even though the HOV lanes in Phoenix may not seem very effective in some ways, they do help more people share rides and make HOV travel better.