Caltrans announced Tuesday its preferred method for improving the 405-101 freeway interchange, which the agency says is one of the busiest in the world. But don't get too excited. The agency also says that it doesn't have the money to design or build the project, which is expected to cost about $135 million. Still, this is one of those classic bottlenecks, and understanding why it doesn't work helps explain a lot of other bottlenecks on Southern California freeways. The big problem is that entrance and exit ramps have been placed too close to one another. The particular issue on the...