More from Pravin Varaiya, who is a research for the Institute of Transportation Studies at UC Berkeley: "They made I-15 in San Diego County into a HOT [High-Occupancy/Toll] Lane. You go through free if you are two people or more, or you can pay a toll. They vary the toll so that that lane doesn't become congested. During rush hour the toll is much higher. It's a free market. It senses the quality of congestion and adjusts the toll accordingly. I think that is a very good idea, and it would benefit everybody."