More highway lanes.
Maybe that's unfair (but, hey, this is a blog). 405 definitely could use a carpool lane. In fact, I think it would even be worth it for California taxpayers to spring for the cost of one. How much do new signs and some white paint cost?
Adding another lane to the highway, besides being shortsighted and defeating the purpose of a carpool lane (to discourage solo driving), would be especially ironic/infuriating given that is less than a mile away from Westwood Village, where Michael Dukakis just became the first person in history to convince Los Angeles leaders that they should dedicate less land to cars.