As anyone knows who drives the region’s freeways, one chronic source of backups is when heavy traffic must cope with an entrance ramp followed closely by an exit ramp. In other words, traffic trying to move left from the entrance lane mixes with traffic trying to move right to exit. The result: a chokepoint causing traffic to back up on the freeway and on surface streets.
There’s a good post on County Supervisor Zev Yaroslavsky’s website explaining that part of the 405 Sepulveda Pass Improvement Project aims to help such a situation at the 405′s junction with Wilshire by building flyover ramps for the northbound and southbound sides of the freeway. As the map above shows (the rendering only shows the southbound ramps), the flyover ramps allow traffic exiting to eastbound Wilshire to leave the freeway before traffic from westbound Wilshire enters.
That, I think, is a key improvement that hasn’t received as much attention as the carpool lane that is being added to the freeway. Of course, it will come with construction headaches, with work expected to begin as early as February. More on that soon and we should be able to show a more detailed rendering next month.