Why not just widen the parallel freeway?
Experience in cities throughout the U.S. has shown that widening freeways can add to capacity but that it also has some severe disadvantages. One is that it doesn’t really reduce congestion for long, as more cars come to take up the added capacity. Another is that it harms the environment by adding to air pollution, noise and visual blight. In addition, it is incredibly expensive, with a total cost possibly eventually exceeding $20 billion for the planned widening of the I-405. This is far higher than the notorious Big Dig freeway project in Boston. Actually, the I-405 freeway has already been widened several times and is currently being widened again, but congestion just keeps getting worse. For a closer look at this issue, please see The Great I-405 Boondoggle.
